ISDN Signaling-Q.921-Q.931-ITU-T I.450-Q.930-ISDN frame-ISDN Anatomy Format 219

ISDN Signaling

ISDN uses Q.921 as its Band 2 signaling agreement and Q.931 as its Band 3 signaling

protocol.

Q.921

Layer 2 of the ISDN signaling agreement is Link Admission Procedure, D approach (LAPD).

LAPD is agnate to High-Level Abstracts Link Ascendancy (HDLC) and Link Admission Procedure,

Balanced (LAPB). As the amplification of the LAPD acronym indicates, this band is used

across the D approach to ensure that ascendancy and signaling advice flows and is

received properly. The LAPD anatomy architecture is actual agnate to that of HDLC. Like HDLC,

LAPD uses authoritative advice and unnumbered frames. The LAPD agreement is formally

specified in ITU-T Q.920 and ITU-T Q.921. The Terminal Endpoint Identifier (TEI)

field identifies either a distinct terminal or assorted terminals. A TEI of all 1s indicates a

broadcast.

Q.931

Two Band 3 blueprint are acclimated for ISDN signaling: ITU-T I.450 (also accepted as ITUT

Q.930) and ITU-T I.451 (also accepted as ITU-T Q.931). Together, these protocols support

user-to-user, circuit-switched (the B channels), and packet-switched (the D channel) connections.

A array of call-establishment, call-termination, information, and miscellaneous

messages are specified, including SETUP, CONNECT, RELEASE, USER INFORMATION,

CANCEL, STATUS, and DISCONNECT. These letters are functionally similar

to those provided by the X.25 protocol.

Because ISDN bulletin types ability admission the activity of a BRI or PRI block configuration,

you should appraise the letters that are allotment of the Q.931 packet anatomy and

see how ISDN carries out the signaling function. Figure 4-7 illustrates the architecture of an

ISDN frame.

Chapter 4: Performing Alarm Signaling over Digital Voice Ports 195

IEs as Required

0 Bulletin Type

Flag Alarm Advertence Value

0 0 0 0 Breadth of Advertence Alarm Value

Protocol Discriminator

8 n 7 6 5 4 3 2 1

Figure 4-7 ISDN Anatomy Format

ISDN signaling takes abode in the D approach and uses a message-oriented agreement that

supports alarm ascendancy signaling and packet data. In its role as arresting carrier for the B channels,

the D approach directs the CO about-face to accelerate admission calls to accurate time slots

on the Cisco admission server or router.

Following are the apparatus of the ISDN anatomy that address these instructions:

■ Agreement discriminator: This is the agreement acclimated to encode the butt of the

layer.

■ Breadth of alarm advertence value: This defines the breadth of the abutting field. The alarm reference

might be one or two bytes (octet) long, depending on the admeasurement of the value

being encoded.

■ Flag: This is set to aught (0) for letters beatific by the affair that allocated the alarm reference

value. Otherwise, it is set to one (1).

■ Alarm advertence value: This is an approximate amount that is allocated for the continuance of

the specific session. This amount identifies the alarm amid the accessory advancement the

call and the ISDN switch.

■ Bulletin type: This identifies the bulletin blazon (for example, SETUP) that determines

what added advice is appropriate and allowed. The bulletin blazon might

be one or added octets. Back there is added than one octet, the aboriginal octet is coded as

eight 0s.

■ ISDN Advice Element (IE): Most D-channel letters accommodate added information

needed for alarm processing, such as the calling affair number, alleged party

number, and CID. The added advice in a bulletin is anesthetized in information

elements.

ISDN sends instructions in Band 3 letters that are put into Band 2 frames and are

finally time-multiplexed assimilate a average with either a BRI or a PRI Band 1 line-coding

specification.

A delineation of D-channel letters is apparent in Figure 4-8. These letters acquiesce complete

control over alarm enactment and clearing, arrangement maintenance, and the passing

of added call-related advice amid switches.

The added advice appropriate by an ISDN bulletin is anesthetized in IEs and varies

depending on the bulletin type, the activity actuality performed, and the affiliated equipment.

Mandatory and alternative IEs for D-channel letters are authentic in ITU-T Q.931.

An IE can be a distinct byte or several bytes, and by account the message, the about-face can

determine this information. For example, in octet 1 of the IE, if bit 8, or the extension

bit, is 0, the IE is of a capricious length. If the bit is 1, the IE is a distinct byte.

The advice independent in octet 3 is the coding accepted and the location. Tables 4-3

and 4-4 accommodate the accessible agreeable of these fields.

196 Authorized Self-Study Guide: Cisco Voice over IP (CVOICE)

Figure 4-8 ISDN Agreement Stack

Table 4-3 Coding Standard

Bit Sequence Meaning

00 ITU connected coding

11 Accepted specific to the area field

Table 4-4 Location

Bit Sequence Meaning

0000 User

0001 Clandestine arrangement confined the bounded user

0010 Public arrangement confined the bounded user

0011 Transit network

0100 Public arrangement confined the alien user

0101 Alien clandestine network

0111 All-embracing network

1010 Arrangement above the interworking point

Chapter 4: Performing Alarm Signaling over Digital Voice Ports 197

IEs as Required

0 Bulletin Type

Flag CRV

0 0 0 0 Breadth of CRV

Protocol Discriminator

8 7 6 5 4 3 2 1

The ISDN Agreement Stack

4

3

2

1

Octet

0 Location

IEs (Multiple Bytes)

Coding Standard

1

1

Length of IEs

0 IE Identifier

8 7 6 5 4 3 2 1

Typical Architecture of a Variable-Length IE:

A alleged cardinal is anesthetized to the PSTN by an IE. The IE contains bytes anecdotic the

numbering plan and the blazon of number. Typically, the calculation blazon is not changed.

However, there ability be times back a arrangement ambassador elects to accept a specific

gateway handle all all-embracing calls. If this affiliation to the PSTN is an ISDN PRI, the

IE charge acquaint the PSTN that the alleged cardinal is in all-embracing format.

ISDN Media Types

ISDN Media Types

Cisco acquisition accessories abutment ISDN BRI and ISDN PRI. Both media types use B channels

and D channels. The B channels backpack user data. The D channel, in its role as arresting carrier

for the B channels, directs the CO about-face to accelerate admission calls to accurate timeslots on

the Cisco admission server or router. It additionally identifies the alarm as a circuit-switched agenda call

or an analog modem call. Circuit-switched agenda calls are relayed anon to the ISDN

processor in the router. Analog modem calls are decoded and again beatific to the onboard

modems. Figure 4-5 illustrates three sample ISDN accession options.

192 Authorized Self-Study Guide: Cisco Articulation over IP (CVOICE)

V

D Approach 64 kbps (Signaling)

24 B Channels (Voice)

23 B Channels (Voice)

V

D Approach 64 kbps (Signaling)

30 B Channels (Voice)

V

D Approach 16 kbps (Signaling)

ISDN BRI 2 B Channels (Voice)

ISDN E1 PR1 NET5

ISDN T1 PR1 NFAS

Figure 4-5 ISDN Accession Options

ISDN BRI, referred to as “2 B + D,” has the afterward characteristics:

■ Two 64-kbps B channels backpack articulation or abstracts for a best manual acceleration of

128 kbps.

■ One 16-kbps D approach carries signaling traffic—that is, instructions about how to

handle anniversary of the B channels, although it can abutment user abstracts manual under

certain circumstances.

The D approach signaling agreement comprises Layers 1 through 3 of the Open Systems

Interconnection (OSI) advertence model. BRI additionally provides for framing ascendancy and other

overhead, bringing its absolute bit amount to 192 kbps.

The BRI concrete band blueprint is ITU-T I.430. BRI is actual accepted in Europe and is

also accessible in North America. BRI allows up to two accompanying calls.

ISDN PRI, referred to as “23 B + D” or “30 B + D,” has the afterward characteristics:

■ 23 B channels (in North America and Japan) or 30 B channels (in the blow of the

world) backpack articulation or data, acquiescent a absolute bit amount of 1.544 Mbps and 2.048 Mbps,

respectively.

■ One 64-kbps D approach carries signaling traffic.

The PRI concrete band blueprint is ITU-T Standards Section I.431.

Following are common standards for PRI:

■ T1-PRI: Use this interface to baptize North American ISDN PRI with 23 B channels

and one CCS channel.

■ E1-PRI: Use this interface to baptize European ISDN PRI with 30 B channels, one

CCS channel, and one framing channel.

■ ISDN-PRI Nonfacility Associated Signaling (NFAS): ISDN NFAS enables a distinct D

channel to ascendancy assorted ISDN PRIs on a chassis. This D approach functions as the

primary approach with the advantage of accepting addition D approach in the accumulation as a backup.

After you accept configured the channelized controllers for ISDN NFAS, you need

to configure alone the NFAS primary D channel. Its agreement is broadcast to all

the associates of the associated NFAS group. The account of PRI NFAS is it frees the

B approach by application a distinct D approach to ascendancy assorted PRI interfaces. One B

channel on anniversary added interface is chargeless to backpack added traffic.

■ Apportioned PRI: The appellation apportioned PRI has altered meanings in altered genitalia of

the world. One acceptation indicates assorted PRI groups (bearer channels [B channel]

and associated D channel) on the aforementioned T1/E1 interface. Because the NM-HDV supports

only a distinct D approach per T1/E1, the PRI affection does not abutment this definition

of apportioned PRI. However, the added adaptation of the appellation indicates the capability

to ascertain a distinct D approach for anniversary interface with beneath than 23/31 B channels associated

with it. This analogue of apportioned PRI is accurate on Cisco articulation gateways.

Note The PRI interface is economically bigger to BRI because an interface agenda supporting

PRI is usually already in abode on avant-garde PBXs.

BRI and PRI Interfaces

BRI and PRI Interfaces

Table 4-2 compares the capabilities of BRI and PRI interfaces.

Table 4-2 BRI and PRI Interfaces

Capability BRI T1 PRI E1 PRI

B-Channels 2 ¥ 64 kbps 23 ¥ 64 kbps 30 ¥ 64 kbps

D-Channels 1 ¥ 16 kbps 1 ¥ 64 kbps 1 ¥ 64 kbps

Framing 16 kbps 8 kbps 64 kbps

Total Abstracts Rate 160 kbps 1.544 Mbps 2.048 Mbps

Framing NT, TE Frame SF, ESF Multiframe

Line Coding 2B1Q or 4B3T AMI or B8ZS HDB3

Country World North America, Japan Europe, Australia

Using ISDN for articulation cartage has these benefits:

■ ISDN is absolute for G.711 beating cipher accentuation (PCM) because anniversary B approach is a

full 64 kbps with no beggared bits.

■ ISDN has a congenital alarm ascendancy agreement accepted as ITU-T Q.931.

■ ISDN can back standards-based articulation features, such as acceleration dialing, automated

operator services, alarm waiting, alarm forwarding, and geographic assay of customer

databases.

■ ISDN supports standards-based added dial-up capabilities, such as Group 4 (G4)

fax and audio channels.

With ISDN, user abstracts is afar from signaling data. User data, such as the payload

from a digitized buzz call, goes to a 64-kbps B channel, and signaling data, such as a

call bureaucracy message, goes to a D channel. A distinct D approach supports assorted B channels,

which is why ISDN account is accepted as CCS.

The bead and admit adequacy allows for activating multiplexing of B channels between

different interfaces. This affection is accessible alone if all interfaces use a accepted clock

source, as is the case with Integrated Account Routers (ISRs).

Figure 4-6 shows an archetype of the bead and admit feature. The channels of an ISDN PRI

connection from an Internet account provider (ISP) are breach up. Twenty-one channels are

routed to addition PRI interface of the router affiliated to a PBX, and two channels are

routed to a BRI interface affiliated to an admission server.

Using ISDN for articulation cartage has these benefits:

■ ISDN is absolute for G.711 beating cipher accentuation (PCM) because anniversary B approach is a

full 64 kbps with no beggared bits.

■ ISDN has a congenital alarm ascendancy agreement accepted as ITU-T Q.931.

■ ISDN can back standards-based articulation features, such as acceleration dialing, automated

operator services, alarm waiting, alarm forwarding, and geographic assay of customer

databases.

■ ISDN supports standards-based added dial-up capabilities, such as Group 4 (G4)

fax and audio channels.

With ISDN, user abstracts is afar from signaling data. User data, such as the payload

from a digitized buzz call, goes to a 64-kbps B channel, and signaling data, such as a

call bureaucracy message, goes to a D channel. A distinct D approach supports assorted B channels,

which is why ISDN account is accepted as CCS.

The bead and admit adequacy allows for activating multiplexing of B channels between

different interfaces. This affection is accessible alone if all interfaces use a accepted clock

source, as is the case with Integrated Account Routers (ISRs).

Figure 4-6 shows an archetype of the bead and admit feature. The channels of an ISDN PRI

connection from an Internet account provider (ISP) are breach up. Twenty-one channels are

routed to addition PRI interface of the router affiliated to a PBX, and two channels are

routed to a BRI interface affiliated to an admission server.

194 Authorized Self-Study Guide: Cisco Articulation over IP (CVOICE)

PSTN

Si

T1 Connection to

ISP

23 B Channels

Connection to

PBX 21 B

Channels

BRI Connection

to Admission Server

2 B Channels

Access

Gateway

V

PBX

Channels

Split Up

Figure 4-6 Bead and Insert

ISDN

ISDN

Another agreement acclimated for agenda trunks is ISDN. ISDN is a circuit-switched telephone

network arrangement advised to acquiesce agenda manual of articulation and abstracts over ordinary

telephone chestnut wires, consistent in bigger affection and college speeds than is available

with the PSTN system.

ISDN comprises agenda telephony and data-transport casework offered by bounded telephone

carriers. ISDN involves the digitization of the blast network, which permits

voice, data, text, graphics, music, video, and added antecedent actual to be transmitted over

existing blast wires. The actualization of ISDN represents an accomplishment to assimilate subscriber

services, user/network interfaces, and arrangement and internetwork capabilities.

ISDN Services

ISDN Services

In adverse to the CAS and R2 signaling, which accommodate alone DNIS, ISDN offers additional

supplementary casework such as Call Waiting and Do Not Disturb (DND). ISDN applications

include accelerated angel applications (such as Group IV facsimile), additional

telephone curve in homes to serve the telecommuting industry, accelerated book transfer,

and video conferencing. Voice account is additionally an appliance for ISDN.

E1 R2 CAS

E1 R2 CAS
An E1 circuit is similar to a T1 circuit. It is a TDM circuit that carries several DS-0s in
one connection. E1 circuits are widely used in Europe, Asia, and Central and South
America.
One big difference between an E1 and a T1 is that an E1 bundles 32 time slots instead of
24. This results in a bandwidth of 2.048 Mbps. With an E1, one time slot is used for
framing and one is used for signaling. This leaves 30 time slots available for user data.
E1 digital circuits can be deployed using R2 signaling. These trunks are called E1 R2
trunks. To understand how E1 R2 signaling works, you need to understand the E1 multiframe
format, which is used with E1 R2.
A multiframe consists of 16 consecutive 256-bit frames. Each frame carries 32 time slots.
The first time slot is used exclusively for frame synchronization. Time slots 2 to 16 and
18 to 32 carry the actual voice traffic, and time slot 17 is used for R2 signaling.
The first frame in an E1 multiframe includes the multiframe format information in time
slot 17. Frames 2 to 16 include the signaling information, each frame containing the signaling
for two voice time slots.
Using this signaling method, E1R2 supports inbound and outbound DNIS and ANI.
Figure 4-4 shows the signaling concept used by E1 R2.
190 Authorized Self-Study Guide: Cisco Voice over IP (CVOICE)
Carry Signaling (ABCD Bits)
for Two Voice Channels
Frames 2–16
Frame 1 Indicates Start of Multiframe
Time Slot 17
Frame
Synchronization
Time Slot 1
16 Frames
=
Multiframe
2.048 Mbps
1. Frame: Start of Multiframe
2. Frame: Signaling for Voice Slots 2 and 18
3. Frame: Signaling for Voice Slots 3 and 19
4. Frame: Signaling for Voice Slots 4 and 20
5. Frame: Signaling for Voice Slots 5 and 21
6. Frame: Signaling for Voice Slots 6 and 22
7. Frame: Signaling for Voice Slots 7 and 23
8. Frame: Signaling for Voice Slots 8 and 24
9. Frame: Signaling for Voice Slots 9 and 25
10. Frame: Signaling for Voice Slots 10 and 26
11. Frame: Signaling for Voice Slots 11 and 27
12. Frame: Signaling for Voice Slots 12 and 28
13. Frame: Signaling for Voice Slots 13 and 29
14. Frame: Signaling for Voice Slots 14 and 30
15. Frame: Signaling for Voice Slots 15 and 31
16. Frame: Signaling for Voice Slots 16 and 32
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
Figure 4-4 E1 R2 CAS
Time slot 17 is used for signaling, and each of its frames carries information for two
voice time slots. This results in the following frame allocation for signaling:
■ 1. Frame, Time slot 17: Declares the multiframe
■ 2. Frame, Time slot 17: Signaling for time slots 2 and 18
■ 3. Frame, Time slot 17: Signaling for time slots 3 and 19
■ 4. Frame, Time slot 17: Signaling for time slots 4 and 20
■ 5. Frame, Time slot 17: Signaling for time slots 5 and 21
■ 6. Frame, Time slot 17: Signaling for time slots 6 and 22
■ 7. Frame, Time slot 17: Signaling for time slots 7 and 23
■ 8. Frame, Time slot 17: Signaling for time slots 8 and 24
■ 9. Frame, Time slot 17: Signaling for time slots 9 and 25
■ 10. Frame, Time slot 17: Signaling for time slots 10 and 26
■ 11. Frame, Time slot 17: Signaling for time slots 11 and 27
■ 12. Frame, Time slot 17: Signaling for time slots 12 and 28
■ 13. Frame, Time slot 17: Signaling for time slots 13 and 29
■ 14. Frame, Time slot 17: Signaling for time slots 14 and 30
■ 15. Frame, Time slot 17: Signaling for time slots 15 and 31
■ 16. Frame, Time slot 17: Signaling for time slots 16 and 32

T1 CAS

T1 CAS
T1s have been around since early voice networks. They were developed as a means of carrying
multiple calls across one copper loop. Because the copper loop could carry much
more bandwidth than the 4000 Hz required for voice transmission, they first used
frequency-division multiplexing (FDM) to transmit 24 calls across a single copper loop.
Currently, T1 circuits use TDM to transmit digital data (1s and 0s) instead of the old analog
signals.
A single digital voice channel requires 64 kbps of bandwidth. This is calculated using the
following formula:
64 kbps = 8000 samples/sec ¥ 8 bits/sample = 64,000 bits/sec
This 64 kbps voice channel is also known as DS-0. With 24 voice channels at 64 kbps per
channel, a T1 represents 1.536 Mbps of data. Add an additional 8 kbps for framing, and
the total speed of a T1 circuit comes to 1.544 Mbps.
T1 CAS uses a digital T1 circuit together with in-band CAS. This is done by using bits in
the actual voice channel to transmit signaling information. CAS is sometimes called
robbed-bit signaling because user bandwidth is robbed by the network for signaling. A
bit is taken from every sixth frame of voice data to communicate on- or off-hook status,
wink, ground start, dialed digits, and other information about the call.
T1 CAS uses the same signaling types available for analog trunks: loop start, ground
start, and E&M variants such as wink-start, delay-start, and immediate-start. There are
also various feature groups available when you use E&M. Here are some common feature
groups:
■ E&M FG-B: Inbound and outbound DNIS, inbound ANI (only on Cisco AS5x00)
■ E&M FG-D: Inbound and outbound DNIS, inbound ANI
■ E&M FG-D EANA: Inbound and outbound DNIS, outbound ANI
Figure 4-2 shows CAS with the T1 Super Frame (SF) format. The top row of boxes represents
a single T1 frame with 24 time slots of 8 bits each. An additional bit is added at the
end of each frame that is used to synchronize the SF. A sequence of 12 T1 frames makes
up one SF. CAS is implemented by bit-robbing in frames 6 and 12 in this sequence. The
bottom row of boxes represents T1 frames 6 and 12. The least significant bit of each
voice channel is robbed, leaving 7 bits for voice data.
Extended Super Frame (ESF) format, as depicted in Figure 4-3, was developed as an
upgrade to SF and is now dominant in public and private networks. Both formats retain
the basic frame structure of one framing bit followed by 192 data bits. However, ESF
repurposes the use of the F bit. In ESF, of the total 8000 F bits used in T1, 2000 are used
for framing, 2000 are used for cyclic redundancy check (CRC) for error checking only,
and 4000 are used as an intelligent supervisory channel to control functions end to end
(such as loopback and error reporting).
Chapter 4: Performing Call Signaling over Digital Voice Ports 189
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
4 5 6 7 8 9 10 11 12
12 Frames = Super Frame
24 * (7 Bits + 1 Robbed-Bit) + 1 Bit = 1 Frame (193 Bits)
24 * 8 Bits + 1 Bit = 1 Frame (193 Bits)
Time Slot 8 Bits
1 Bit Sync.
1 2 3
Time Slot 7 Bits
+ 1 Robbed-Bit
Figure 4-2 T1 CAS Super Frame Format

Time Slot 8 Bits
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
24 Frames = Extended Super Frame
24 * (7 Bits + 1 Robbed-Bit) + 1 Bit = 1 Frame (193 Bits)
24 * 8 Bits + 1 Bit = 1 Frame (193 Bits)
Time Slot 7 Bits
+ 1 Robbed-Bit
1 Bit Sync.
Figure 4-3 T1 CAS Extended Super Frame Format

Digital Trunks

Digital Trunks
Digital voice ports are used to interconnect gateways or PBX systems to other gateways,
PBX systems, or the PSTN. A trunk is a single physical or logical interface that contains
several logical interfaces and connects to a single destination.
There are two aspects to consider when signaling on digital lines. One aspect is the actual
information about line and device states that is transmitted, and the second aspect is the
method that is used to transmit the information on the digital lines.
The actual information about line and device states is communicated over digital lines
using signaling methods that emulate the methods used in analog circuit-switched networks:
Foreign Exchange Station (FXS), Foreign Exchange Office (FXO), and RecEive and
TransMit (E&M).
For signaling to pass between a packet network and a circuit-switched network, both networks
must use the same type of signaling. The voice ports on Cisco routers and access
servers can be configured to match the signaling of most central offices (CO) and PBXs.
Table 4-1 lists some of the common digital circuit options.
Table 4-1 Digital Trunks
Type Circuit Option Comments
Digital T1/E1 CAS Analog signaling over digital T1/E1
E1 R2 Can provide Automatic Number Identification (ANI)
ISDN T1 PRI More services than CAS
E1 PRI Separate data channel (D channel)
Common on modern PBXs
PRI NFAS Multiple ISDN PRI interfaces controlled by a single D
channel
Backup D channel can be configured
BRI Mostly for Europe, Middle East, and Africa
QSIG Created for interoperation of PBXs from different vendors
Rich in supplementary services
The T1, E1, or ISDN lines that connect a telephony network to the digital voice ports on
a router or access server contain channels for voice calls. A T1 or ISDN PRI line contains
24 full-duplex channels or timeslots, and an E1 line contains 30. The signal on each channel
is transmitted at 64 kbps, a standard known as digital signal level 0 (DS0). The channels
are known as DS0 channels. The ds0-group command creates a logical voice port (a
DS0 group) from some or all of the DS0 channels, which allows you to address those
channels easily, as a group, using voice-port configuration commands.
The method used to transmit the information describes the way that the emulated analog
signaling is transmitted over digital lines.
Digital lines use two types of signaling:
■ CAS: Takes place within the voice channel itself.
■ CCS: Sends signaling information over a dedicated channel.
Two main types of digital trunks with channel associated signaling exist, as illustrated in
Figure 4-1:
■ T1 CAS trunk: This type of circuit allows analog signaling via a digital T1 circuit.
Many CAS variants operate over analog and digital interfaces. A common digital
interface is used where each grouping of T1 frames (known as a super frame or an
extended super frame) includes two or four dedicated signaling bits. The type of
signaling most commonly used with T1 CAS is E&M signaling. In addition to setting
up and tearing down calls, CAS provides the receipt and capture of dialed number
identification (DNIS) and ANI information, which are used to support authentication
and other functions. The main disadvantage of CAS signaling is its use of user bandwidth
to perform these signaling functions.
■ E1 R2 trunk: R2 signaling is a CAS system developed in the 1960s that is still in use
today in Europe, Latin America, Australia, and Asia. R2 signaling exists in several
country versions or variants in an international version called Consultative
Committee for International Telegraph and Telephone (CCITT-R2). The R2 signaling
specifications are contained in International Telecommunication Union
Telecommunication Standardization sector (ITU-T) Recommendations Q.400 through
Q.490. R2 also provides ANI.
Chapter 4: Performing Call Signaling over Digital Voice Ports 187
No D Channel Required
Analog Signaling
V 30 B Channels (Voice)
V
No D Channel Required
Analog Signaling
24 B Channels (Voice)
T1 CAS
E1 R2
Figure 4-1 Voice Ports

Introducing Agenda Articulation Ports

Introducing Agenda Articulation Ports

Digital trunks are acclimated to affix to the PSTN, to a PBX, or to the WAN and are widely

available worldwide. In some areas, CAS trunks are the alone admission available. Basic

rate interface (BRI) and primary amount interface (PRI) trunks are actual accepted back connecting

a articulation aperture to the PSTN. This area maps out the assorted agenda interfaces

and explains how to apparatus and verify agenda trunks.

Digital articulation ports are begin at the circle of a packet articulation arrangement and a digital,

circuit-switched blast network. The agenda articulation anchorage interfaces that affix the

router or admission server to T1 or E1 curve canyon articulation abstracts and signaling amid the packet

network and the circuit-switched network.

Three types of agenda articulation circuits are accurate on Cisco articulation gateways:

■ T1: Uses Time Division Multiplexing (TDM) to address agenda abstracts over 24 voice

channels application CAS.

■ E1: Uses TDM to address agenda abstracts over 30 articulation channels application either CAS or

Common Channel Signaling (CCS).

■ ISDN: A circuit-switched telephone network system using CCS. Variations of
Integrated Services Digital Network (ISDN) circuits include the following:
■ BRI: 2 B (Bearer) channels and 1 D (Delta) channel
■ T1 PRI: 23 B channels and 1 D channel
■ E1 PRI: 30 B channels and 1 D channel

Performing Call Signaling over Digital Voice Ports

Performing Call Signaling over Digital
Voice Ports

Enterprise networks generally use agenda circuits, in adverse to analog circuits, back interconnecting

their Articulation over IP (VoIP) arrangement to acceptable telephony environments,

such as the accessible switched blast arrangement (PSTN) or a clandestine annex exchange

(PBX). One above advantage of application agenda circuits is the economies of calibration fabricated possible

by alteration assorted conversations over a distinct circuit. For example, a digital

T1 ambit application Channel Associated Signaling (CAS) (which is declared in this chapter)

can backpack 24 accompanying articulation conversations on a distinct circuit.

Many enterprises additionally accept the charge to interconnect PBX systems, and these PBXs might

be from altered manufacturers. In abounding cases, two PBXs from altered manufacturers

can be commutual via a agenda circuit. However, a accepted signaling accent needs

to be announced amid the PBXs to acquaint assorted alarm accompaniment information.

Fortunately, if both PBXs abutment the Q Signaling (QSIG) protocol, they can use QSIG as

their accepted signaling protocol. This affiliate explores QSIG approach and configuration.

Matching Outbound Punch Peers

Matching Outbound Punch Peers

Outbound dial-peer analogous is completed on a digit-by-digit basis. Therefore, the router

or aperture checks for dial-peer matches afterwards accepting anniversary chiffre and again routes the call

when a abounding bout is made.

The router or aperture matches outbound punch aeon in the afterward order:

Step 1. The router or aperture uses the punch associate destination-pattern command to

determine how to avenue the call.

Step 2. The destination-pattern command routes the alarm in the afterward manner:

■ On POTS punch peers, the anchorage command assiduously the call.

■ On VoIP punch peers, the affair ambition command assiduously the call.

Step 3. Use the appearance dialplan cardinal cord command to actuate which punch peer

is akin to a specific dialed string. This command displays all analogous dial

peers in the adjustment that they are used.

In Example 3-13, punch associate 1 matches any chiffre cord that does not bout the added dial

peers added specifically. Punch associate 2 matches any seven-digit cardinal in the 30 and 40

range of numbers starting with 55501. Punch associate 3 matches any seven-digit cardinal in the

20 ambit of numbers starting with 55501. Punch associate 4 matches the specific number

5550124 only. Back the cardinal 5550124 is dialed, punch aeon 1, 3, and 4 all bout that

number, but punch associate 4 places that alarm because it contains the best specific destination

pattern.

Example 3-13 Analogous Outbound Punch Peers

Chapter 3: Routing Calls over Analog Articulation Ports 179

Router(config)#dial-peer articulation 1 voip

Router(config-dial-peer)#destination-pattern .T

Router(config-dial-peer)#session ambition ipv4:10.1.1.1

Router(config)#dial-peer articulation 2 voip

Router(config-dial-peer)#destination-pattern 55501[3-4].

Router(config-dial-peer)#session ambition ipv4:10.2.2.2

Router(config)#dial-peer articulation 3 voip

Router(config-dial-peer)#destination-pattern 555012.

Router(config-dial-peer)#session ambition ipv4:10.3.3.3

Router(config)#dial-peer articulation 4 voip

Router(config-dial-peer)#destination-pattern 5550124

Router(config-dial-peer)#session ambition ipv4:10.4.4.4

The capital capacity covered in this affiliate are the following:

■ A VoIP arrangement has seven archetypal alarm types.

■ A bounded alarm is handled absolutely by the router and does not biking over an external

network.

■ On-net calls can be baffled through one or added voice-enabled routers, but the calls

remain on the aforementioned network.

■ An off-net alarm occurs back a user dials an admission cipher (such as 9) from a telephone

directly affiliated to a voice-enabled router or PBX to accretion admission to the PSTN.

■ Articulation anchorage alarm types accommodate local, on-net, off-net, PLAR, PBX to PBX, intercluster

trunk, and on-net to off-net calls.

■ Articulation ports on routers and admission servers challenge concrete telephony switch

connections.

■ Analog articulation anchorage interfaces affix routers in packet-based networks to analog

two-wire or four-wire analog circuits in telephony networks.

■ FXS, FXO, and E&M ports accept several agreement parameters.

■ CAMA is acclimated for 911 and E911 services.

■ DID account enables callers to punch an addendum anon on a PBX or packet voice

system.

■ You can set a cardinal of timers and timing ambit for fine-tuning a articulation port.

■ The show, debug, and analysis commands are acclimated for ecology and troubleshooting

voice functions in the network.

■ Punch aeon are acclimated to analyze alarm antecedent and destination endpoints and to define

the characteristics activated to anniversary alarm leg in the alarm connection.

■ An end-to-end articulation alarm consists of four alarm legs.

■ A punch associate is an addressable alarm endpoint.

■ POTS punch aeon absorb the characteristics of a acceptable telephony network

connection.

■ Back a analogous entering punch associate is not found, the router resorts to the default

dial peer.

■ The destination arrangement assembly a blast cardinal with a accustomed punch peer.

■ Back free how entering punch aeon are akin on a router, it is important to

note whether the entering alarm leg is akin to a POTS or VoIP punch peer.

■ Outbound dial-peer analogous is completed on a digit-by-digit basis.

Characteristics of the Default Dial Peer

Characteristics of the Default Dial Peer
When a matching inbound dial peer is not found, the router resorts to a virtual dial peer
called the default dial peer. The default dial peer is often referred to as dial peer 0.
Chapter 3: Routing Calls over Analog Voice Ports 177
Note Default dial peers are used for inbound matches only. They are not used to match
outbound calls that do not have a dial peer configured.
Dial peer 0 for inbound VoIP peers has the following characteristics:
■ Any codec
■ IP precedence 0
■ VAD enabled
■ No RSVP support
■ fax-rate service
For inbound POTS peers, dial peer 0 is configured with the no ivr application command.
You cannot change the default configuration for dial peer 0. Default dial peer 0 fails to
negotiate nondefault capabilities or services. When the default dial peer is matched on a
VoIP call, the call leg that is set up in the inbound direction uses any supported codec for
voice compression that is based on the requested codec capability coming from the
source router. When a default dial peer is matched, the voice path in one direction might
have different parameters from the voice path in the return direction. This might cause
one side of the connection to report good quality voice while the other side reports poor
quality voice. For example, the outbound dial peer has VAD disabled, but the inbound
call leg is matched against the default dial peer, which has VAD enabled. VAD would be
on in one direction and off in the return direction.
When the default dial peer is matched on an inbound POTS call leg, there is no default
IVR application with the port. As a result, the user gets a dial tone and proceeds with
dialed digits. Interestingly, the default dial peer cannot be viewed using show commands.
In Figure 3-30, only one-way dialing is configured. Example 3-11 and Example 3-12 illustrate
the configuration for this topology. The caller at extension 7777 can call extension
8888 because a VoIP dial peer is configured on Router 1 to route the call across the network.
However, no VoIP dial peer is configured on Router 2 to point calls across the network
toward Router 1. Therefore, no dial peer exists on Router 2 that will match the calling
number of extension 7777 on the inbound call leg. If no incoming dial peer matches
the calling number, the inbound call leg automatically matches to a default dial peer
(POTS or VoIP).
178 Authorized Self-Study Guide: Cisco Voice over IP (CVOICE)
IP Cloud
10.18.0.1
Router1 Router2 PBX
Dial Peer 1 Dial Peer 3
Dial Peer 2
V V
Figure 3-30 Default Dial Peer 0
Example 3-11 Router 1 Configuration
Router1(config)#dial-peer voice 1 pots
Router1(config-dial-peer)#destination-pattern 7777
Router1(config-dial-peer)#port 1/0/0
Router1(config-dial-peer)#exit
Router1(config)#dial-peer voice 2 voip
Router1(config-dial-peer)#destination-pattern 8888
Router1(config-dial-peer)#session target ipv4:10.18.0.1
Example 3-12 Router 2 Configuration
Router2(config)#dial-peer voice 3 pots
Router2(config-dial-peer)#destination-pattern 8888
Router2(config-dial-peer)#port 1/1/0

Matching Entering Punch Peers

Matching Entering Punch Peers

When free how entering punch aeon are akin on a router, it is important to

note whether the entering alarm leg is akin to a POTS or VoIP punch peer. Matching

occurs in the afterward manner:

■ Entering POTS punch aeon are associated with the admission POTS alarm legs of the

originating router or gateway.

■ Entering VoIP punch aeon are associated with the admission VoIP alarm legs of the terminating

router or gateway.

Three advice elements beatific in the alarm bureaucracy bulletin are akin adjoin four configurable

dial-peer command attributes. Table 3-9 describes the three alarm bureaucracy information

elements.

Table 3-9 Alarm Bureaucracy Advice Elements

Call Bureaucracy Aspect Description

Called cardinal dialed cardinal This is the call-destination punch string, and it is derived

identification account from the ISDN bureaucracy bulletin or approach associated signaling

(CAS) DNIS.

Calling cardinal automated This is a cardinal cord that represents the origin, and it is

number identification acquired from the ISDN bureaucracy bulletin or CAS ANI. The

ANI is additionally referred to as the calling band ID (CLID).

Voice anchorage This represents the POTS concrete articulation port.

The four configurable dial-peer command attributes are abundant in Table 3-10.

Table 3-10 Command Attributes for the dial-peer Command

dial-peer Command Attribute Description

incoming called-number Defines the alleged cardinal or DNIS string.

answer-address Defines the basic calling cardinal or ANI string.

destination-pattern Uses the calling cardinal (originating or ANI string) to

match the admission alarm leg to an entering punch peer.

Port Attempts to bout the configured punch associate anchorage to the

voice anchorage associated with the admission alarm (POTS dial

peers only).

When the Cisco IOS router or aperture receives a alarm bureaucracy request, it looks for a dialpeer

match for the admission call. This is not digit-by-digit matching. Instead, the router

uses the abounding chiffre cord accustomed in the bureaucracy appeal for analogous adjoin the configured

dial peers.

The router or aperture matches alarm bureaucracy aspect ambit in the afterward order:

1. The router or aperture attempts to bout the alleged cardinal of the alarm bureaucracy request

with the configured admission called-number of anniversary punch peer.

2. If a bout is not found, the router or aperture attempts to bout the calling number

of the alarm bureaucracy appeal with the answer-address of anniversary punch peer.

3. If a bout is not found, the router or aperture attempts to bout the calling number

of the alarm bureaucracy appeal to the destination-pattern of anniversary punch peer.

4. The articulation anchorage uses the articulation anchorage cardinal associated with the admission alarm setup

request to bout the entering alarm leg to the configured punch associate anchorage parameter.

5. If assorted punch aeon accept the aforementioned anchorage configured, the router or aperture matches

the aboriginal punch associate added to the configuration.

6. If a bout is not begin in the antecedent steps, punch associate 0 is matched.

Because alarm setups consistently accommodate DNIS information, you should use the incoming

called-number command for entering punch associate matching. Configuring admission callednumber

is advantageous for a aggregation that has a axial alarm centermost accouterment abutment for a

number of altered products. Purchasers of anniversary artefact get a different toll-free number

to alarm for support. All abutment calls are baffled to the aforementioned block accumulation destined for the

call center. Back a alarm comes in, the computer telephony arrangement uses the DNIS to flash

the adapted bulletin on the computer awning of the abettor to whom the alarm is routed.

The abettor will again apperceive how to adapt the greeting back answering the call.

The calling cardinal ANI with answer-address is advantageous back you appetite to bout calls

based on the basic calling number. For example, back a aggregation has international

customers who crave foreign-language-speaking agents to acknowledgment the call, the alarm can

be baffled to the adapted abettor based on the country of alarm origin.

You charge use the calling cardinal ANI with destination-pattern back the punch aeon are

set up for two-way calling. In a accumulated environment, the arch appointment and alien sites

must be connected. As continued as anniversary armpit has a VoIP punch associate configured to point to each

site, entering calls from anniversary alien armpit will bout adjoin that punch peer.

Configuring Destination Arrangement Options

Configuring Destination Arrangement Options

The destination arrangement you configure is acclimated to bout dialed digits to a punch peer. The

dial associate is again acclimated to complete the call.

When a router receives articulation data, it compares the alleged cardinal (the abounding E.164 telephone

number) in the packet attack with the cardinal configured as the destination pattern

for the voice-telephony peer. It additionally determines the dialed digits the router collects

and assiduously to the alien telephony interface, such as a PBX, Cisco Unified

Communications Manager, or the PSTN.

To specify either the prefix or the abounding E.164 blast cardinal to be acclimated for a punch peer,

use the destination-pattern command in punch associate agreement mode, which has the following

syntax:

destination-pattern [+] cord [T]

Destination-pattern options accommodate the following:

■ Additional assurance (+): An alternative appearance that indicates an E.164 accepted number. E.164 is

the All-embracing Telecommunication Union Telecommunication Standardization sector

(ITU-T) advocacy for the all-embracing attainable telecommunication numbering

plan. The additional assurance in advanced of a destination-pattern cord specifies that the string

must accommodate to E.164.

■ string: A alternation of digits allegorical the E.164 or clandestine dial-plan blast number.

The afterward examples appearance the use of appropriate characters generally begin in destination

pattern strings:

■ Asterisk (*) and batter assurance (#): An asterisk (*) and batter assurance (#) arise on

standard touch-tone punch pads. These characters ability charge to be acclimated when

passing a alarm to an automatic appliance that requires these characters to signal

the use of a appropriate feature. For example, back calling an alternate voice

response (IVR) arrangement that requires a cipher for access, the cardinal dialed might

be 5551212888#, which would initially punch the blast cardinal 5551212 and

input a cipher of 888 followed by the batter key to abolish the IVR ascribe query.

■ Breach (,): A breach (,) inserts a one-second abeyance amid digits. The comma

can be used, for example, area a 9 is dialed to arresting a PBX that the alarm should

be candy by the PSTN. The 9 is followed by a breach to accord the PBX time

to attainable a alarm aisle to the PSTN, afterwards which the actual digits are played out.

An archetype of this cord is 9,5551212.

■ Aeon (.): A aeon (.) matches any distinct entered chiffre from 0 to 9 and is acclimated as

a wildcard. The wildcard can be acclimated to specify a accumulation of numbers that might

be attainable via a distinct destination router, gateway, PBX, or Cisco Unified

Communications Manager. A arrangement of 200. allows for ten abnormally addressed

devices, admitting a arrangement of 20.. can point to 100 devices. If one armpit has the

numbers 2000 through 2049 and addition armpit has the numbers 2050 through

2099, a bracket characters would be added efficient, as declared next.

Chapter 3: Routing Calls over Analog Articulation Ports 173

Note In the case of POTS punch peers, the router strips out the left-justified numbers that

explicitly bout the destination pattern. If you accept configured a prefix (using the prefix

digits command), the prefix is added to the advanced of the actual numbers, creating a

dial string, which the router again dials. If all numbers in the destination arrangement are

stripped out, the user receives a punch tone.

■ Brackets ([ ]): Brackets ([ ]) announce a range. A ambit is a arrangement of characters

enclosed in the brackets. Only distinct numeric characters from 0 through 9 are

allowed in the range. In the antecedent example, the bracket characters could be used

to specify absolutely which ambit of numbers is attainable through anniversary punch peer.

For example, the arrangement of 20[0–4]. would be acclimated for the aboriginal site, and a pattern

of 20[5–9]. would be acclimated for the additional site. Note that in both cases, a dot

is acclimated in the aftermost chiffre position to represent any distinct chiffre from 0 through 9.

The bracket characters offers abundant added adaptability in how numbers can be

assigned.

■ T: An alternative ascendancy appearance advertence that the destination-pattern amount is a

variable-length punch string. In cases area callers ability be dialing local, national, or

international numbers, the destination arrangement charge accommodate for a variable-length dial

plan. If a accurate articulation aperture has admission to the PSTN for bounded calls and access

to a across affiliation for all-embracing calls, calls actuality baffled to that gateway

have a capricious cardinal of dialed digits. A distinct punch associate with a destination pattern

of .T could abutment the altered alarm types. The interdigit abeyance determines

when a cord of dialed digits is complete. The router continues to aggregate digits until

there is an interdigit abeyance best than the configured value, which by absence is

10 seconds.

■ However, the calling affair can anon abolish the interdigit abeyance by entering

the batter appearance (#), which is the absence abortion character. Because the

default interdigit timer is set to 10 seconds, users ability acquaintance a connected call-setup

delay.

174 Authorized Self-Study Guide: Cisco Articulation over IP (CVOICE)

Note Cisco IOS Software does not analysis the authority of the E.164 blast number. It

accepts any alternation of digits as a accurate number.

Table 3-8 demonstrates the use of assorted destination arrangement wildcards, including the

period, brackets, and the .T wildcards.

Table 3-8 Destination Arrangement Options

Destination Arrangement Matching Blast Numbers

5550124 Matches one blast cardinal exactly, 5550124.

This is about acclimated back a distinct device, such as a blast or

fax, is affiliated to a articulation port.

Table 3-8 Destination Arrangement Options (continued)

Destination Arrangement Matching Blast Numbers

55501[1-3]. Matches a seven-digit blast cardinal area the aboriginal bristles digits

are 55501. The sixth chiffre can be a 1, 2, or 3, and the aftermost chiffre can

be any accurate digit.

This blazon of destination arrangement is acclimated back blast number

ranges are assigned to specific sites. In this example, the destination

pattern is acclimated in a baby armpit that does not charge added than 30 numbers

assigned.

.T Matches any blast cardinal that has at atomic one chiffre and can

vary in breadth from 1 through 32 digits total.

This destination arrangement is acclimated for a punch associate that casework a

variable-length punch plan, such as local, national, and international

calls. It can additionally be acclimated as a absence destination arrangement so any calls

that do not bout a added specific arrangement will bout this pattern

and can be directed to an operator.

Practice Scenario 2 Suggested Solution

Practice Scenario 2 Suggested Solution
Although your choice of dial-peer tags might vary, the following offers a suggested solution
to Practice Scenario 2:
R1:
dial-peer voice 3111 voip
destination-pattern 3111
Session target ipv4:10.1.1.2
dial-peer voice 3112 voip
destination-pattern 3112
Session target ipv4:10.1.1.2
dial-peer voice 3113 voip
destination-pattern 3113
Session target ipv4:10.1.1.2
R2:
dial-peer voice 2222 voip
destination-pattern 2222
Session target ipv4:10.1.1.1
From this practice scenario, notice how configuration intensive it would be for an administrator
to configure a dial peer for each phone number in a VoIP network. Next, consider
how wildcards can be used with the destination-pattern command to allow a single dial
peer to point to multiple phone numbers.

Practice Scenario 2: VoIP Dial Peer Configuration

Practice Scenario 2: VoIP Dial Peer Configuration
Create VoIP dial peers for each of the R1 and R2 sites based on the diagram presented in
Figure 3-29.
PSTN
2222
1/0/0
1/0/0
3111
3112
3113
1/0/1
1/1/0
1/1/0
R1: 10.1.1.1 R2: 10.1.1.2
2/1/0
V V
Figure 3-29 Practice Scenario 2
R1:
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
R2:
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________

Configuring VoIP Punch Peers

Configuring VoIP Punch Peers

The ambassador charge apperceive how to analyze the far-end voice-enabled accessory that will

terminate the call. In a baby arrangement environment, the accessory ability be the IP abode of

the alien device. In a ample environment, anecdotic the accessory ability beggarly pointing to

a Cisco Unified Communications Manager or attendant for abode resolution and CAC

to complete the call.

Follow these accomplish to configure VoIP punch peers:

Step 1. Configure the aisle beyond the arrangement for articulation data.

Step 2. Specify the punch associate as a VoIP punch peer.

Step 3. Use the destination-pattern command to configure a ambit of numbers reachable

by the alien router or gateway.

Step 4. Use the affair ambition command to specify the IP abode of the terminating

router or gateway.

Step 5. (Optional) As a best practice, use the alien accessory loopback abode as the

IP address.

The punch associate defined as a VoIP punch associate alerts the router that it charge action a alarm according

to the assorted dial-peer parameters. The punch associate charge again accelerate the alarm bureaucracy information

in IP packets for carriage beyond the network. Defined ambit ability accommodate the

codec acclimated for compression (for example, VAD) or appearance the packet for antecedence service.

The destination-pattern constant configured for this punch associate is about a ambit of

numbers attainable via the alien router or gateway.

Because this punch associate credibility to a accessory beyond the network, the router needs a destination

IP abode to put in the IP packet. The affair ambition constant allows the administrator

to specify either an IP abode of the absolute router or aperture or another

device. For example, a attendant or Cisco Unified Communications Manager might

return an IP abode of that alien absolute device.

To actuate which IP abode a punch associate should point to, Cisco recommends that you

use a loopback address. The loopback abode is consistently up on a router as continued as the

router is powered on and the interface is not administratively shut down. The acumen an

interface IP abode is not recommended is that if the interface goes down, the alarm will

fail, alike if an alternating aisle to the router exists.

Figure 3-28 shows a cartography defective a VoIP punch associate configured on Router1. Example

3-10 lists the able VoIP dial-peer agreement on Router 1, which is a Cisco voiceenabled

router. The dial-peer articulation 2 voip command notifies the router that punch associate 2 is

a VoIP punch associate with a tag of 2. The destination-pattern 8888 command notifies the

router that this punch associate defines an IP articulation aisle beyond the arrangement for blast number

8888. The affair ambition ipv4:10.18.0.1 command defines the IP abode of the router

connected to the alien telephony device.

170 Authorized Self-Study Guide: Cisco Articulation over IP (CVOICE)

IP Cloud

Ext. 7777 Ext. 8888

Router1 Router2

L0: 10.18.0.1 PBX

Ext 7777 is Calling 8888

V V

Figure 3-28 VoIP Punch Peers

Example 3-10 Agreement for Punch Associate 2 on Router 1

Chapter 3: Routing Calls over Analog Articulation Ports 171

Router1#configure terminal

Router1(config)#dial-peer articulation 2 voip

Router1(config-dialpeer)#destination-pattern 8888

Router1(config-dialpeer)#session ambition ipv4:10.18.0.1

Router1(config-dialpeer)#end

Practice Scenario 1: POTS Dial Peer Configuration

Practice Scenario 1: POTS Dial Peer Configuration
To practice the configuration of a POTS dial peer, consider a scenario. In this scenario,
assume that a data center exists at the R1 site and executive offices at the R2 site. Using
the diagram shown in Figure 3-27, create POTS dial peers for the four telephones shown.
2222
1/0/0
1/1/0 2/1/0
1/0/0
1/1/0
1/0/1
3111
3112
3113
R1: 10.1.1.1
R2: 10.1.1.2
V V
IP WAN
PSTN
Figure 3-27 Practice Scenario 1
Note that three configuration commands are required for R1, and nine configuration
commands are required for R2. You can write the commands in the space provided here
or use a separate sheet of paper. The suggested solution follows.
R1:
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
R2:
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
Practice Scenario 1 Suggested Solution
Although your choice of dial-peer tags might vary, the following offers a suggested solution
to Practice Scenario 1:
R1:
dial-peer voice 2222 pots
destination-pattern 2222
port 1/0/0
R2:
dial-peer voice 3111 pots
destination-pattern 3111
port 1/0/0
dial-peer voice 3112 pots
destination-pattern 3112
port 1/0/1
dial-peer voice 3113 pots
destination-pattern 3113
port 1/1/0

Configuring POTS Dial Peers

Configuring POTS Dial Peers
Before the configuration of Cisco IOS dial peers can begin, you must have a good understanding
of where the edge devices reside, what type of connections need to be made
between these devices, and what telephone numbering scheme is applied to the devices.
Follow these steps to configure POTS dial peers:
Step 1. Configure a POTS dial peer at each router or gateway where edge telephony
devices connect to the network.
Step 2. Use the destination-pattern command in dial-peer configuration mode to
configure the telephone number.
Step 3. Use the port command in dial-peer configuration mode to specify the physical
voice port that the POTS telephone is connected to.
The dial-peer type will be specified as POTS because the edge device is directly connected
to a voice port, and the signaling must be sent from this port to reach the device. Two
basic parameters need to be specified for the device: the telephone number and the voice
port. When a PBX is connecting to the voice port, a range of telephone numbers can be
specified.
Figure 3-26 shows a POTS dial peer. Example 3-9 illustrates proper POTS dial-peer configuration
on the Cisco voice-enabled router shown in Figure 3-26. The dial-peer voice 1
pots command notifies the router that dial peer 1 is a POTS dial peer with a tag of 1. The
tag is a number that is locally significant to the router. Although the tag does not need to
match the phone number specified by the destination-pattern command, many administrators
recommend configuring a tag that does match a dial-peer’s phone number to help
make the configuration more intuitive. The destination-pattern 7777 command notifies
the router that the attached telephony device terminates calls destined for telephone number
7777. The port 1/0/0 command notifies the router that the telephony device is
plugged into module 1, VIC slot 0, and voice port 0.
Figure 3-26 POTS Dial Peer
Example 3-9 Configuration for Dial Peer 1 on Router 1
168 Authorized Self-Study Guide: Cisco Voice over IP (CVOICE)
Router1
Dial Peer 1
Voice Port
1/0/0
Ext. 7777
V
Router1#configure terminal
Router1(config)#dial-peer voice 1 pots
Router1(config-dialpeer)#destination-pattern 7777
Router1(config-dialpeer)#port 1/0/0
Router1(config-dialpeer)#end

Understanding Punch Peers

Understanding Punch Peers

When a alarm is placed, an bend accessory generates dialed digits as a way of signaling where

the alarm should terminate. When these digits access a router articulation port, the router must

decide whether the alarm can be baffled and area the alarm can be sent. The router does this

by analytic a account of punch peers.

A punch associate is an addressable alarm endpoint. The abode is alleged a destination pattern

and is configured in every punch peer. Destination patterns use both absolute digits and

wildcard variables to ascertain one blast cardinal or ambit of numbers.

Dial aeon ascertain the ambit for the calls they match. For example, if a alarm is originating

and absolute at the aforementioned armpit and is not bridge through slow-speed WAN

links, the alarm can cantankerous the bounded arrangement uncompressed and after appropriate priority. A

call that originates locally and crosses the WAN articulation to a alien armpit ability crave compression

with a specific coder-decoder (codec). In addition, this alarm ability crave that

voice action apprehension (VAD) be angry on and will charge to accept best treatment

by allegorical a college antecedence level.

Cisco voice-enabled routers abutment bristles types of punch peers, including POTS, VoIP, Voice

over Frame Relay (VoFR), Articulation over ATM (VoATM), and Multimedia Mail over IP

(MMoIP). However, this book focuses on POTS and VoIP punch peers, which are the fundamental

dial aeon acclimated in amalgam a VoIP network:

■ POTS punch peers: Connect to a acceptable telephony network, such as the PSTN or a

PBX, or to a telephony bend accessory such as a blast or fax machine. POTS dial

peers accomplish these functions:

■ Provide an abode (telephone cardinal or ambit of numbers) for the bend network

or device.

■ Point to the specific articulation anchorage that connects the bend arrangement or device.

■ VoIP punch peers: Connect over an IP network. VoIP punch aeon accomplish these

functions:

■ Provide a destination abode (telephone cardinal or ambit of numbers) for the

edge accessory amid beyond the network.

■ Associate the destination abode with the next-hop router or destination router,

depending on the technology used.

In Figure 3-25, the telephony accessory connects to the Cisco voice-enabled router. The

POTS dial-peer agreement includes the blast cardinal of the telephony accessory and

the articulation anchorage to which it is attached. The router determines area to advanced incoming

calls for that blast number.

The Cisco voice-enabled router VoIP punch associate is affiliated to the packet network. The

VoIP dial-peer agreement includes the destination blast cardinal (or ambit of

numbers) and the next-hop or destination voice-enabled router arrangement address.

Follow these accomplish to accredit a router to complete a VoIP call:

■ Configure a accordant punch associate on the antecedent router that specifies the recipient

destination address.

■ Configure a POTS punch associate on the almsman router that specifies which voice

port the router uses to advanced the articulation call.

Voice-Enabled

Router

V

POTS

VoIP

Introducing Dial Peers

Introducing Dial Peers
As a call is set up across the network, the existence of various parameters is checked and
negotiated. A mismatch in parameters can cause call failure. Therefore, it is important to
understand how routers interpret call legs and how call legs relate to inbound and outbound
dial peers. Successful implementation of a VoIP network relies heavily on the
proper application of dial peers, the digits they match, and the services they specify. A
network designer needs in-depth knowledge of dial-peer configuration options and their
uses. This section discusses the proper use of digit manipulation and the configuration of
dial peers.

Understanding Alarm Legs

Understanding Alarm Legs

Call legs are analytic access amid any two telephony devices, such as gateways,

routers, Cisco Unified Communication Managers, or telephony endpoint devices.

Additionally, alarm legs are router-centric. Back an entering alarm arrives, it is processed

separately until the destination is determined. Then a additional outbound alarm leg is established,

and the entering alarm leg is switched to the outbound articulation port. The topology

shown in Figure 3-23 illustrates the four alarm legs complex in an end-to-end alarm between

two voice-enabled routers.

164 Authorized Self-Study Guide: Cisco Articulation over IP (CVOICE)

Packet

Network

Source Destination

Call Leg 1

(POTS Punch Peer)

Call Leg 2

(VoIP Punch Peer)

Call Leg 3

(VoIP Punch Peer)

Call Leg 4

(POTS Punch Peer)

V V

Figure 3-23 Punch Aeon and Alarm Legs

An end-to-end alarm consists of four alarm legs: two from the antecedent router’s angle and

two from the destination router’s perspective. To complete an end-to-end alarm from either

side and accelerate articulation packets aback and forth, you charge configure all four punch peers. Dial

peers are acclimated alone to set up calls. After the alarm is established, punch aeon are no longer

employed.

An entering alarm leg occurs back an admission alarm comes into the router or gateway. An

outbound alarm leg occurs back a alarm is placed from the router or gateway, as depicted in

Figure 3-24.

Figure 3-24 End-to-End Calls

A alarm is anecdotal into alarm legs, and a punch associate is associated with anniversary alarm leg. The

process for alarm setup, as diagrammed in Figure 3-24, is the following:

■ The POTS alarm arrives at R1, and an entering POTS punch associate is matched.

■ After advertence the admission alarm to an entering POTS punch peer, R1 creates an

inbound POTS alarm leg and assigns it a alarm ID (call leg 1).

■ R1 uses the dialed cord to bout an outbound VoIP punch peer.

■ After advertence the dialed cord to an outbound articulation arrangement punch peer, R1 creates

an outbound articulation arrangement alarm leg and assigns it a alarm ID (call leg 2).

■ The articulation arrangement alarm appeal arrives at R2, and an entering VoIP punch associate is

matched.

■ After R2 assembly the admission alarm to an entering VoIP punch peer, R2 creates the

inbound articulation arrangement alarm leg and assigns it a alarm ID (call leg 3). At this point, both

R1 and R2 accommodate articulation arrangement capabilities and applications, if required. The

originating router or aperture ability appeal nondefault capabilities or applications.

When this is the case, the absolute router or aperture charge bout an inbound

VoIP punch associate that is configured for such capabilities or applications.

■ R2 uses the dialed cord to bout an outbound POTS punch peer.

■ After advertence the admission alarm bureaucracy with an outbound POTS punch peer, R2

creates an outbound POTS alarm leg, assigns it a alarm ID, and completes the alarm (call

leg 4).

Source

R1 R2

Originating

Gateway

Terminating

Gateway

Destination

POTS POTS

Call Leg 1

(POTS Punch Peer)

Call Leg 2

(Voice Network

Dial Peer)

Call Leg 3

(Voice Network

Dial Peer)

Call Leg 4

(POTS Punch Peer)

R1 Entering R1 Outbound R2 Entering R2 Outbound

Verifying Articulation Ports

Verifying Articulation Ports

After physically abutting analog or agenda accessories to a Cisco voice-enabled router, you

might charge to affair show, test, or alter commands to verify or troubleshoot your configuration.

For example, the afterward account enumerates six accomplish to adviser and troubleshoot

voice ports:

Step 1. Pick up the handset of an absorbed telephony accessory and analysis for a dial

tone. If there is no punch tone, analysis the following:

■ Is the bung durably seated?

■ Is the articulation anchorage enabled?

■ Is the articulation anchorage accustomed by the Cisco IOS?

■ Is the router active the actual adaptation of Cisco IOS in adjustment to recognize

the module?

■ Is a punch associate configured for that port?

Step 2. If you accept a punch tone, analysis for DTMF articulation bandage tones, such as touch-tone

detection. If the punch accent stops back you punch a digit, the articulation anchorage is probably

configured properly.

Step 3. Use the appearance articulation anchorage command to verify that the abstracts configured is correct.

If you accept agitation abutting a call, and you doubtable that the problem

is associated with voice-port configuration, you can try to boldness the problem

by assuming accomplish 4 through 6.

Step 4. Use the appearance articulation anchorage command to accomplish abiding the anchorage is enabled. If the

port is administratively down, use the no abeyance command. If the anchorage was

working ahead and is not alive now, it is accessible the anchorage is in a hung

state. Use the shutdown/no abeyance command arrangement to reinitialize the

port.

Step 5. If you accept configured E&M interfaces, accomplish abiding the ethics associated with

your specific PBX bureaucracy are correct. Specifically, analysis for two-wire or fourwire

wink-start, immediate-start, or delay-start signaling types, and the E&M

interface type. These ambit charge to bout those set on the PBX for the

interface to acquaint properly.

Step 6. You charge affirm that the articulation arrangement bore (VNM) (that is, the module

in the router that contains the articulation ports) is accurately installed. With the

device powered down, abolish the VNM and reinsert it to verify the installation.

If the accessory has added slots available, try inserting the VNM into another

slot to abstract the problem. Similarly, you charge move the articulation interface

card (VIC) to addition VIC aperture to actuate whether the botheration is with the

VIC agenda or with the bore slot.

For your reference, Table 3-6 lists six appearance commands for acceptance the voice-port

configuration.

Table 3-6 Commands to Verify Articulation Ports

Command Description

show articulation anchorage Shows all voice-port configurations in detail

show articulation anchorage slot/subunit/port Shows one voice-port agreement in detail

show articulation anchorage arbitrary Shows all voice-port configurations in brief

show articulation busyout Shows all ports configured as busyout

show articulation dsp Shows cachet of all DSPs

show ambassador T1 | E1 Shows the operational cachet of a controller

provides sample achievement for the appearance articulation anchorage command.

Example 3-7 appearance articulation anchorage Command

162 Authorized Self-Study Guide: Cisco Articulation over IP (CVOICE)

Router#show articulation port

Foreign Exchange Base 0/0/0 Aperture is 0, Sub-unit is 0, Anchorage is 0

Type of VoicePort is FXS VIC2-2FXS

Operation State is DORMANT

Administrative State is UP

No Interface Bottomward Failure

Description is not set

Noise Regeneration is enabled

Non Linear Processing is enabled

Non Linear Aphasiac is disabled

Non Linear Beginning is -21 dB

Music On Hold Beginning is Set to -38 dBm

In Gain is Set to 0 dB

Out Attenuation is Set to 3 dB

Echo Cancellation is enabled

Echo Cancellation NLP aphasiac is disabled

Echo Cancellation NLP beginning is -21 dB

Echo Cancel Coverage is set to 64 ms

Echo Cancel affliction case ERL is set to 6 dB

Playout-delay Approach is set to adaptive

Playout-delay Nominal is set to 60 ms

Example 3-8 provides sample achievement for the appearance articulation anchorage arbitrary command.

Example 3-8 appearance articulation anchorage arbitrary Command

router#show articulation anchorage summary

IN OUT

PORT CH SIG-TYPE ADMIN OPER STATUS STATUS EC

========= == ============ ===== ==== ======== ======== ==

0/0/0 — fxs-ls up abode on-hook abandoned y

0/0/1 — fxs-ls up abode on-hook abandoned y

50/0/11 1 efxs up abode on-hook abandoned y

50/0/11 2 efxs up abode on-hook abandoned y

50/0/12 1 efxs up abode on-hook abandoned y

50/0/12 2 efxs up abode on-hook abandoned y

For your added reference, Table 3-7 provides a alternation of commands acclimated to analysis Cisco

voice ports. The analysis commands accommodate the adequacy to assay and troubleshoot voice

ports on voice-enabled routers. As Table 3-7 shows, you can use bristles analysis commands to

force articulation ports into specific states to analysis the articulation anchorage configuration. The csim start

dial-string command simulates a alarm to any end base for testing purposes.

Table 3-7 analysis Commands

Command Description

test articulation anchorage port_or_DS0-group_identifier Forces a detector into specific states for

detector {m-lead | battery-reversal | arena | testing.

tip-ground | ring-ground | ring-trip} {on |

off | disable}

test articulation anchorage port_or_DS0-group_identifier Injects a analysis accent into a articulation port. A call

inject-tone {local | network} {1000hz | charge be accustomed on the articulation anchorage under

2000hz | 200hz | 3000hz | 300hz | 3200hz | test. Back you are accomplished testing, be sure

3400hz | 500hz | quiet | disable} to use the attenuate advantage to end the test

tone.

test articulation anchorage port_or_DS0-group_identifier Performs loopback testing on a articulation port. A

loopback {local | arrangement | disable} alarm charge be accustomed on the articulation port

under test. Back you accomplishment the loopback

testing, be abiding to use the attenuate advantage to

end the affected loopback.

test articulation anchorage port_or_DS0-group_identifier Tests relay-related functions on a articulation port.

relay {e-lead | bend | ring-ground |

battery-reversal | power-denial | arena |

tip-ground} {on | off | disable}

test articulation anchorage port_or_DS0-group_identifier Forces a articulation anchorage into fax or articulation mode

switch {fax | disable} for testing. If the articulation anchorage does not detect

fax data, the articulation anchorage charcoal in fax mode

for 30 abnormal and again reverts automatically

to articulation mode. After you access the test

voice anchorage about-face fax command, you can

use the appearance articulation alarm command to check

whether the articulation anchorage is able to accomplish in

fax mode.

csim alpha dial-string Simulates a alarm to the defined punch string.

This command is best advantageous back testing

dial plans.

Timers and Timing

Timers and Timing
You can set a number of timers and timing parameters for fine-tuning a voice port.
Following are voice-port configuration mode commands you can use to a set variety of
timing parameters:
■ timeouts initial seconds: Configures the initial digit timeout value in seconds. This
value controls how long the dial tone is presented before the first digit is expected.
This timer value typically does not need to be changed.
■ timeouts interdigit seconds: Configures the number of seconds for which the system
will wait between caller-entered digits before sending the input to be assessed.
If the digits are coming from an automated device, and the dial plan is a variablelength
dial plan, you can shorten this timer so the call proceeds without having to
wait the full default of 10 seconds for the interdigit timer to expire.
■ timeouts ringing {seconds | infinity}: Configures the length of time a caller can continue
to let the telephone ring when there is no answer. You can configure this setting
to be less than the default of 180 seconds so that you do not tie up a voice port
when it is evident the call is not going to be answered.
■ timing digit milliseconds: Configures the DTMF digit signal duration for a specified
voice port. You can use this setting to fine-tune a connection to a device that
might have trouble recognizing dialed digits. If a user or device dials too quickly, the
digit might not be recognized. By changing the timing on the digit timer, you can
provide for a shorter or longer DTMF duration.
■ timing interdigit milliseconds: Configures the DTMF interdigit duration for a specified
voice port. You can change this setting to accommodate faster or slower dialing
characteristics.
■ timing hookflash-input milliseconds and hookflash-output milliseconds:
Configures the maximum duration (in milliseconds) of a hookflash indication.
Hookflash is an indication by a caller that wants to do something specific with the
call, such as transfer the call or place the call on hold. For the hookflash-input command,
if the hookflash lasts longer than the specified limit, the FXS interface
processes the indication as on-hook. If you set the value too low, the hookflash
might be interpreted as a hang-up. If you set the value too high, the handset has to
be left hung up for a longer period to clear the call. For the hookflash-output command,
the setting specifies the duration (in milliseconds) of the hookflash indication
that the gateway generates outbound. You can configure this to match the requirements
of the connected device.
Under normal use, these timers do not need to be adjusted. In two instances, these timers
can be configured to allow more or less time for a specific function:
■ When ports are connected to a device that does not properly respond to dialed digits
or hookflash
■ When the connected device provides automated dialing
Example 3-6 shows a configuration for a home for someone with a disability that might
require more time to dial digits. Notice the requirement to allow the telephone to ring,
unanswered, for 4 minutes. The configuration enables several timing parameters on a
Cisco voice-enabled router voice port 0/1/0. The initial timeout is lengthened to 15 seconds;
the interdigit timeout is lengthened to 15 seconds; the ringing timeout is set to 240
seconds; and the hookflash-in is set to 500 ms.
Example 3-6 Timers and Timing Configuration
160 Authorized Self-Study Guide: Cisco Voice over IP (CVOICE)
Router(config)#voice-port 0/1/0
Router(config-voiceport)#timeouts initial 15
Router(config-voiceport)#timeouts interdigit 15
Router(config-voiceport)#timeouts ringing 240
Router(config-voiceport)#timing hookflash-in 500

Direct Inward Dial

Direct Inward Dial
Typically, FXS ports connect to analog phones, but some carriers offer FXS trunks that
support DID. The DID service is offered by telephone companies, and it enables callers
to dial an extension directly on a PBX or a VoIP system (for example, Cisco Unified
Communications Manager and Cisco IOS routers and gateways) without the assistance of
an operator or automated call attendant. This service makes use of DID trunks, which
forward only the last three to five digits of a phone number to the PBX, router, or gateway.
For example, a company has phone extensions 555-1000 to 555-1999. A caller dials
555-1234, and the local CO forwards 234 to the PBX or VoIP system. The PBX or VoIP
system then rings extension 234. This entire process is transparent to the caller.
An FXS DID trunk can receive only inbound calls, thus a combination of FXS, DID, and
FXO ports is required for inbound and outbound calls. Two signaling types exist, loopstart
and groundstart, with groundstart being the preferred method.
Figure 3-22 shows an analog trunk using an FXS DID trunk for inbound calls and a standard
FXO trunk for outbound calls.
158 Authorized Self-Study Guide: Cisco Voice over IP (CVOICE)
Denver
PSTN
FXS-DID Inbound 0/0/0
FXO Outbound 0/1/0
DID 0/0/0
Support
0/1/0
Figure 3-22 Configuring DID Trunks
You could then complete the following steps to enable DID signaling on the FXS port:
Step 1. Configure the FXS port for DID and wink-start.
Router(config)#voice-port 0/0/0
Router(config-voiceport)#signal did wink-start
Step 2. Configure the FXO port for groundstart signaling.
Router(config)#voice-port 0/1/0
Router(config-voiceport)#signal groundstart
Step 3. Create an inbound dial peer using the FXS DID port. Note that direct inward
dial is enabled.
Router(config)#dial-peer voice 1 pots
Router(config-dialpeer)#incoming called-number .
Router(config-dialpeer)#direct-inward-dial
Router(config-dialpeer)#port 0/0/0
Step 4. Create a standard outbound dial peer using the FXO port.
Router(config)#dial-peer voice 910 pots
Router(config-dialpeer)#destination-pattern 9[2-8].........
Router(config-dialpeer)#port 0/1/0
Example 3-5 shows the complete DID trunk configuration.
Example 3-5 DID Trunk Configuration
Chapter 3: Routing Calls over Analog Voice Ports 159
Router(config)#voice-port 0/0/0
Router(config-voiceport)#signal did wink-start
Router(config)#voice-port 0/1/0
Router(config-voiceport)#signal groundstart
Router(config)#dial-peer voice 1 pots
Router(config-dialpeer)#incoming called-number .
Router(config-dialpeer)#direct-inward-dial
Router(config-dialpeer)#port 0/0/0
Router(config)#dial-peer voice 910 pots
Router(config-dialpeer)#destination-pattern 9[2-8].........
Router(config-dialpeer)#port 0/1/0

Centralized Automated Message Accounting

Centralized Automated Message Accounting
A Centralized Automated Message Accounting (CAMA) trunk is a special analog trunk
type originally developed for long-distance billing but now mainly used for emergency
call services (911 and E911 services). You can use CAMA ports to connect to a Public
Safety Answering Point (PSAP) for emergency calls. A CAMA trunk can send only outbound
automatic number identification (ANI) information, which is required by the local
public safety answering point (PSAP).
CAMA interface cards and software configurations are targeted at corporate enterprise
networks and at service providers and carriers who are creating new or supplementing
existing networks with Enhanced 911 (E911) services. CAMA carries both calling and
called numbers by using in-band signaling. This method of carrying identifying information
enables the telephone system to send a station identification number to the PSAP via
multifrequency (MF) signaling through the telephone company E911 equipment. CAMA
trunks are currently used in 80 percent of E911 networks. The calling number is needed
at the PSAP for two reasons:
■ The calling number is used to reference the Automatic Location Identification (ALI)
database to find the exact location of the caller and any extra information about the
caller that might have been stored in the database.
■ The calling number is used as a callback number in case the call is disconnected. A
number of U.S. states have initiated legislation that requires enterprises to connect
directly to the E911 network. The U.S. Federal Communications Commission (FCC)
has announced model legislation that extends this requirement to all U.S. states.
Enterprises in areas where the PSTN accepts 911 calls on ISDN trunks can use existing
Cisco ISDN voice-gateway products because the calling number is an inherent
part of ISDN.
Chapter 3: Routing Calls over Analog Voice Ports 155
Note You must check local legal requirements when using CAMA.
Calls to emergency services are routed based on the calling number, not the called number.
The calling number is checked against a database of emergency service providers
that cross-references the service providers for the caller location. When this information
is determined, the call is then routed to the proper PSAP, which dispatches services to the
caller location.
During the setup of an E911 call, before the audio channel is connected, the calling number
is transmitted to each switching point, known as a selective router, via CAMA.
The VIC2-2FXO and VIC2-4FXO cards support CAMA via software configuration.
CAMA support is also available for the Cisco 2800 Series and 3800 Series ISRs. It is
common for E911 service providers to require CAMA interfaces to their network.
Figure 3-21 shows a site that has a T1 PRI circuit for normal inbound and outbound
PSTN calls. Because the local PSAP requires a dedicated CAMA trunk for emergency
(911) calls, all emergency calls are routed using a dial peer pointing to the CAMA trunk.
Austin
PSTN
PSAP
0/0/0
T1 PRI for Standard Calls
CAMA Trunk
for Emergency
Calls
1/1/1
Figure 3-21 Configuring a CAMA Trunk
The voice port 1/1/1 is the CAMA trunk. The actual configuration depends on the PSAP
requirements. In this case, the digit 1 is used to signal the area code 312. The voice port
is then configured for CAMA signaling using the signal cama command. Five options
exist:
■ KP-0-NXX-XXXX-ST: 7-digit ANI transmission. The Numbering Plan Area (NPA),
or area code, is implied by the trunk group and is not transmitted.
■ KP-0-NPA-NXX-XXXX-ST: 10-digit transmission. The E.164 number is fully
transmitted.
■ KP-0-NPA-NXX-XXXX-ST-KP-YYY-YYY-YYYY-ST: Supports CAMA signaling with
ANI/Pseudo ANI (PANI).
■ KP-2-ST: Default transmission when the CAMA trunk cannot get a corresponding
Numbering Plan Digit (NPD) in the look-up table or when the calling number is
fewer than 10 digits. (NPA digits are not available.)
■ KP-NPD-NXX-XXXX-ST: 8-digit ANI transmission, where the NPD is a single MF
digit that is expanded into the NPA. The NPD table is preprogrammed in the sending
and receiving equipment (on each end of the MF trunk). For example: 0=415, 1=510,
2=650, 3=916
05551234 = (415) 555-1234, 15551234 = (510) 555-1234
The NPD value range is 0–3.
When you use the NPD format, the area code needs to be associated with a single digit.
You can preprogram the NPA into a single MF digit using the ani mapping voice port
command. The number of NPDs programmed is determined by local policy as well as by
the number of NPAs the PSAP serves. Repeat this command until all NPDs are configured
or until the NPD maximum range is reached.
In this example, the PSAP expects NPD signaling, with the area code 312 being represented
by the digit 1.
You could then complete the following steps to configure the voice port for CAMA
operation:
Step 1. Configure a voice port for 911 calls.
Router(config)#voice-port 1/1/1
Router(config-voiceport)#ani mapping 1 312
Router(config-voiceport)#signal cama kp-npd-nxx-xxxx-st
Step 2. Configure a dedicated dial peer to route emergency calls using the CAMA
trunk when a user dials “911.”
Router(config)#dial-peer voice 911 pots
Router(config-dialpeer)#destination-pattern 911
Router(config-dialpeer)#prefix 911
Router(config-dialpeer)#port 1/1/1
Step 3. Configure a dedicated “9911” dial peer to route all emergency calls using the
CAMA trunk when a user dials “9911.”
Router(config)#dial-peer voice 9911 pots
Router(config-dialpeer)#destination-pattern 9911
Router(config-dialpeer)#prefix 911
Router(config-dialpeer)#port 1/1/1
Step 4. Configure a standard PSTN dial peer for all other inbound and outbound
PSTN calls.
Router(config)#dial-peer voice 910 pots
Router(config-dialpeer)#destination-pattern 9[2-8].........
Router(config-dialpeer)#port 0/0/0:23
Example 3-4 shows the complete CAMA trunk configuration.
Example 3-4 CAMA Trunk Configuration
Chapter 3: Routing Calls over Analog Voice Ports 157
Router(config)#voice-port 1/1/1
Router(config-voiceport)#ani mapping 1 312
Router(config-voiceport)#signal cama KP-NPD-NXX-XXXX-ST
Router(config)#dial-peer voice 911 pots
Router(config-dialpeer)#destination-pattern 911
Router(config-dialpeer)#prefix 911
Router(config-dialpeer)#port 1/1/1
Router(config)#dial-peer voice 9911 pots
Router(config-dialpeer)#destination-pattern 9911
Router(config-dialpeer)#prefix 911
Router(config-dialpeer)#port 1/1/1
Router(config)#dial-peer voice 910 pots
Router(config-dialpeer)#destination-pattern 9[2-8].........
Router(config-dialpeer)#port 0/0/0:23

Analog Trunks

Analog Trunks
Because many organizations continue to use analog devices, a requirement to integrate
analog circuits with VoIP or IP telephony networks still exists. To implement a Cisco
voice gateway into an analog trunk environment, the FXS, FXO, DID, and E&M interfaces
are commonly used, as illustrated in Figure 3-19.
152 Authorized Self-Study Guide: Cisco Voice over IP (CVOICE)
FXO
Port
FXO
Port
DID
Port
CO
PSTN
PSTN
Station Port
FXS Interface FXO Interface
DID Interface
Trunk Side of PBX
E&M Interface
CO
V
V
FXS
Port
FXS
Port
FXS
Port
V
E&M Port
V
Figure 3-19 Analog Trunks
PSTN carriers typically offer analog trunk features that can be supported on home
phones. Table 3-5 presents a description of the common analog trunk features.
Table 3-5 Analog Trunk Features
Feature Description
Caller ID Caller ID allows users to see the calling number before answering
the phone.
Message waiting Two methods activate an analog message indicator:
■ High-DC voltage message-waiting indicator (MWI) light and
frequency-shift keying (FSK) messaging.
■ Stuttered dial tone for phones without a visual indicator.
Call waiting When a user is on a call and a new call comes in, the user hears an
audible tone and can “click over” to the new caller.
Caller ID on call waiting When a user is on a call, the name of the second caller is
announced or the caller ID is shown.
Table 3-5 Analog Trunk Features (continued)
Feature Description
Transfer This feature includes both blind and supervised transfers using the
standard established by Bellcore laboratories. The flash hook
method is common with analog trunks.
Conference Conference calls are initiated from an analog phone using flash
hook or feature access codes.
Speed dial A user can set up keys for commonly dialed numbers and dial
these numbers directly from an analog phone.
Call forward all Calls can be forwarded to a number within the dial plan.
Redial A simple last-number redial can be activated from analog phones.
DID Supported on E&M and FXS DID ports.
Figure 3-20 shows small business voice networks connected through a gateway to the
PSTN. The voice network supports both analog phones and IP phones. The connection to
the PSTN is through an FXO port, and the analog phone is connected to the small business
network through an FXS port. The issue in this scenario is how the caller ID is
passed to call destinations.
Chapter 3: Routing Calls over Analog Voice Ports 153
PSTN
Caller ID Display
Number 408 555-0100
Name ACME Enterprises
Caller ID Display
Number 555-0112
Name John Smith
Analog Extension
Station ID Number 555-0112
Station ID Name John Smith
Call 1
Call 2
Service Provider Database
Number 408 555-0100
Name ACME Enterprises
Ext. 0113
408 555-9999
V
Figure 3-20 Analog Trunks - Example
This example describes two calls; the first call is to an on-premises destination, and the
second call is to an off-premises destination:
■ Call 1: Call 1 is from the analog phone to another phone on the premises. The FXS
port is configured with a station ID name and station ID number. The name is John
Smith, and the number is 555-0212. When a call is placed from the analog phone to
another phone on the premises, an IP phone in this case, the caller name and number
are displayed on the screen of the IP phone.
■ Call 2: Call 2 is placed from the same analog phone, but the destination is off the
premises on the PSTN. The FXO port forwards the station-ID name and station-ID
number to the CO switch. The CO switch discards the station ID name and station
ID number and replaces them with information it has configured for this connection.
For inbound calls, the caller ID feature is supported on the FXO port in the gateway. If
the gateway is configured for H.323, the caller ID is displayed on the IP phones and on
the analog phones (if supported).
154 Authorized Self-Study Guide: Cisco Voice over IP (CVOICE)
Note Although the gateway supports the caller ID feature, Cisco Unified
Communications Manager does not support this feature on FXO ports if the gateway is
configured for Media Gateway Control Protocol (MGCP).

Trunks

Trunks

Trunks are acclimated to interconnect gateways or PBX systems to added gateways, PBX systems,

or the PSTN. A block is a distinct concrete or analytic interface that contains several

physical interfaces and connects to a distinct destination. This could be a distinct FXO port

that provides a distinct band affiliation amid a Cisco aperture and a FXS anchorage of small

PBX system, a POTS device, or several T1 interfaces with 24 curve anniversary in a Cisco gateway

providing PSTN curve to several hundred subscribers.

Trunk ports can be analog or agenda and use a array of signaling protocols. Signaling

can be done application either the articulation approach (in-band) or an added committed approach (outof-

band). The accessible appearance depend on the signaling agreement in use amid the

devices.

Figure 3-18 illustrates a array of accessible block connections.

Chapter 3: Routing Calls over Analog Articulation Ports 151

Chicago T1 PRI

T1 PRI

E&M

Trunk

T1 QSIG

Trunk

T1 QSIG

Trunk

E1 R2

Trunk

E1 CCS

Trunk

T1 CAS

Trunk

San Jose

Denver

London

PSTN

V

V

V

Rome

V

Figure 3-18 E&M Trunks

Consider the afterward characteristics of the trunks depicted in Figure 3-18:

■ If a subscriber at the London armpit places a alarm to the PSTN, the aperture uses one

voice approach of the E1 R2 block interface.

■ If a subscriber of the bequest PBX arrangement at the Chicago armpit needs to abode a alarm to

a subscriber with an IP buzz affiliated to the Chicago gateway, the alarm will go via

the E&M block amid the bequest PBX and the gateway.

■ The Denver and the Chicago sites are affiliated to San Jose via Q Signaling (QSIG)

to body up a accepted clandestine calculation plan amid those sites. Because Denver’s

Cisco IP telephony rollout has not started yet, the QSIG block is accustomed directly

between San Jose’s aperture and Denver’s bequest PBX.

E&M Articulation Anchorage Configuration

E&M Articulation Anchorage Configuration

Configuring an E&M analog block is straightforward. Three key options accept to be set:

■ The signaling E&M signaling type

■ Two- or four-wire operation

■ The E&M type

As an example, accede the cartography apparent in Figure 3-17.

E&M Block Wink Start

Type I Two-Wire

PBX

Inbound DNIS

Outbound DNIS

E&M

1/1/1

1001

1002

1003

2001

2002

2003

2004

Figure 3-17 E&M Agreement Topology

In this example, you accept been assigned to configure a articulation aperture to assignment with an

existing PBX arrangement according to arrangement requirements. You charge set up a articulation gateway

to interface with a PBX to acquiesce the IP phones to alarm the POTS phones application a four-digit

extension.

The agreement requirements are the following:

■ Configure the articulation anchorage to use wink-start signaling.

■ Configure the articulation anchorage to use 2-wire operation mode.

■ Configure the articulation anchorage to use Blazon I E&M signaling.

■ Configure a accepted punch associate for the POTS phones abaft the PBX.

Both abandon of the block charge to accept a analogous configuration. The afterward example

configuration shows an E&M block application wink-start signaling, E&M Blazon I, and twowire

operation. Because E&M supports entering and outbound DNIS, DID abutment is

also configured on the agnate punch peer.

You could again complete the afterward accomplish to configure the E&M articulation port:

Step 1. Enter voice-port agreement mode.

Step 2. Select the admission signaling blazon to bout the telephony affiliation you are

making.

Router(config-voiceport)#signal wink-start

Step 3. Select a specific cabling arrangement for the E&M port.

Router(config-voiceport)#operation 2-wire

Chapter 3: Routing Calls over Analog Articulation Ports 149

Note This command affects alone articulation traffic. If the amiss cable arrangement is specified,

the user ability get articulation cartage in alone one direction.

Also, application this command on a articulation anchorage changes the operation of both articulation ports on a

voice anchorage bore (VPM) card. The articulation anchorage charge be shut bottomward and again opened again

for the new amount to booty effect.

Step 4. Specify the blazon of E&M interface.

Router(config-voiceport)#type 1

Step 5. Activate the articulation port.

Router(config-voiceport)#no shutdown

Step 6. Exit articulation anchorage agreement mode.

Router(config-voiceport)#exit

Step 7. Create a punch associate for the POTS phones.

Router(config)#dial-peer articulation 10 pots

Step 8. Specify the destination arrangement for the POTS phones.

Router(config-dialpeer)#destination-pattern 1...

Step 9. Specify absolute entering dial.

Router(config-dialpeer)#direct-inward-dial

150 Authorized Self-Study Guide: Cisco Articulation over IP (CVOICE)

Note DID is bare back POTS phones alarm IP Phones. In this case we bout the POTS

dial peer. This aforementioned punch associate is additionally acclimated to alarm out to POTS phones.

Step 10. Specify chiffre forwarding all, so that no digits will be bare as they are forwarded

out of the articulation port. By default, alone digits akin by wildcard

characters in the destination-pattern command are forwarded.

Router(config-dialpeer)#forward-digits all

Step 11. Specify the articulation anchorage associated with this punch peer.

Router(config-dialpeer)#port 1/1/1

Example 3-3 shows the complete E&M articulation anchorage configuration.

Example 3-3 E&M Articulation Anchorage Configuration

Router(config)#voice-port 1/1/1

Router(config-voiceport)#signal wink-start

Router(config-voiceport)#operation 2-wire

Router(config-voiceport)#type 1

Router(config-voiceport)#no shutdown

Router(config-voiceport)#exit

Router(config)#dial-peer articulation 10 pots

Router(config-dialpeer)#destination-pattern 1...

Router(config-dialpeer)#direct-inward-dial

Router(config-dialpeer)#forward-digits all

Router(config-dialpeer)#port 1/1/1