Providing Alarm Acceptance Ascendancy with H.323
In this section, you will apprentice how to apparatus gatekeeper-based CAC. You will also
learn how CAC is alive and how it is amenable for managing acceptance ascendancy and
bandwidth for both articulation and video calls. Further, you will apprentice the functions of the
RAI apparatus and how it is configured in an H.323 network.
Gatekeeper Area Bandwidth Operation
Consider the Cisco Unified IP Communications arrangement apparent in Figure 8-38. Because
the IP arrangement is based on a packet-switched arrangement (PSN), no committed circuits are
established to set up an IP communications call. Instead, the IP packets absolute the
voice samples are baffled beyond the IP arrangement calm with added types of abstracts packets.
QoS is acclimated to differentiate the articulation packets from the abstracts packets, but bandwidth
resources, abnormally on IP WAN links, are not infinite. Therefore, arrangement administrators
dedicate a assertive bulk of “priority” bandwidth to articulation cartage on anniversary IP WAN link.
However, afterwards the provisioned bandwidth has been absolutely utilized, the Cisco Unified IP
Communications arrangement charge adios consecutive calls to abstain oversubscription of the
priority chain on the IP WAN link, which would account affection abasement for all voice
calls.
Chapter 8: Configuring H.323 Gatekeepers 505
IP WAN
PSTN
Router1
(H.323)
San Jose
Gatekeeper
Phone1-1
2001
Phone2-1
3001
Phone1-2
2002
Phone2-2
3002
Router2
(H.323)
There is no limitation on the
number of calls beyond IP links.
However, if QoS is configured
for one call, added calls
can go through, but the voice
quality of all calls degrades.
CAC helps to anticipate link
oversubscription.
GK
V V
2
1
Figure 8-38 Dial-Peer Agreement Topology
This action is accepted as CAC and is capital to agreement acceptable articulation affection in a multisite
deployment. The attendant maintains a almanac of all alive calls so it can manage
bandwidth in a zone.
You can use CAC to advice advance a adapted akin of articulation affection over a WAN link. For
example, you can use CAC to adapt the articulation affection on a T1 band that connects your
main campus to a alien site.
CAC regulates articulation affection by attached the cardinal of calls that can be alive on a particular
link at the aforementioned time. CAC does not agreement a accurate akin of audio quality
on the link, but it does acquiesce you to adapt the bulk of bandwidth captivated by
active calls on the link.
The Cisco IOS attendant is the accessory in the IP communications arrangement that is responsible
for CAC amid these devices:
■ Cisco Unified Communications Manager
■ Cisco Unified Communications Manager Express
■ H.323 gateways
The attendant requires a changeless policy-based agreement of the accessible resources.
The attendant cannot accredit capricious assets like the Resource Reservation Protocol
(RSVP) is able to do.
Zone Bandwidth Calculation
Zone bandwidth in a attendant arrangement can be affected with this simple formula:
(Number of Calls) * (Codec Payload Bandwidth) * 2 = Area Bandwidth
With this formula, the bare bandwidth in a attendant arrangement can be calmly defined.
For example, afterward is a adding for three accompanying G.711 calls in a gatekeeper
network:
3 * 64 kbps * 2 = 384 kbps
An important point for every bandwidth adding is the cardinal of accessories for which
you appetite to account the bandwidth. Gatekeepers and Cisco Unified Communications
Manager servers accept altered bandwidth ethics for the aforementioned codecs. In a Cisco Unified
Communications Manager environment, a G.711 alarm is affected to use 80 kbps, and a
G.729 alarm is affected to use 24 kbps. However, in a attendant environment, a G.711 call
consumes 128 kbps, and a G.729 alarm consumes 16 kbps. If a alarm is signaled from a Cisco
Unified Communications Manager server to a gatekeeper, Cisco Unified Communications
Manager internally assumes that 80 kbps of bandwidth is appropriate for a G.711 call, but
will arresting in its ARQ bulletin to its attendant a appeal for a G.711 alarm with 128 kbps
of bandwidth required. Similarly, back application G.729, Cisco Unified Communications
Manager will use 24 kbps for centralized CAC calculations, but appeal 16 kbps from a
gatekeeper.
Example 8-22 shows a attendant with an alive G.711 alarm requested by Cisco Unified
Communications Manager. Note the 128 kbps in the “BW” column.
Example 8-22 Viewing Alive Attendant Calls
506 Authorized Self-Study Guide: Cisco Articulation over IP (CVOICE)
GK#show attendant calls
Total cardinal of alive calls = 1.
GATEKEEPER CALL INFO
====================
LocalCallID Age(secs) BW
2-14476 59 128(Kbps)
Endpt(s): Alias E.164Addr
src EP: CHI-CUCME 13125553001
CallSignalAddr Port RASSignalAddr Port
192.168.3.254 1720 192.168.3.254 52668
Endpt(s): Alias E.164Addr
dst EP: ipipgw 49895556666
CallSignalAddr Port RASSignalAddr Port
192.168.1.3 1720 192.168.1.3 52060
The attendant is the axial accessory in the network. The bandwidth is configured for the
network on the gatekeeper. The accessible bandwidth will be arrested by the gatekeeper
for every call, as illustrated in Figure 8-39.
Chapter 8: Configuring H.323 Gatekeepers 507
IP WAN
PSTN
Router1
(H.323)
Zone SanJose Area Chicago
Gatekeeper
Phone1-1
2001
Phone2-1
3001
Phone1-2
2002
Phone2-2
3002
Router2
(H.323)
Bandwidth agreement for all zones
is done on the gatekeeper.
GK1
V V
Figure 8-39 Area Bandwidth Sample Topology
The bandwidth command allows the attendant to administer the bandwidth limitations
within a zone, beyond zones, and at a per-session level. By default, the best aggregate
bandwidth is unlimited.
Example 8-23 configures the absence best bandwidth for cartage amid one zone
and addition area to 128 kbps, the absence best bandwidth for all zones to 5 Mbps,
the absence best bandwidth for a distinct affair aural any area up to 384 kbps, and
the absence best bandwidth for a distinct affair with area “Denver” of up to
256 kbps.
Example 8-23 Area Bandwidth Command Example
GK1(config)#gatekeeper
GK1(config-gk)#bandwidth interzone absence 128
GK1(config-gk)#bandwidth absolute absence 5000
GK1(config-gk)#bandwidth affair absence 384
GK1(config-gk)#bandwidth affair area denver 256
The bandwidth Command
The abounding command syntax for the bandwidth command is as follows:
bandwidth {interzone | absolute | affair | alien | check-destination} {default |
zone zone-name} bandwidth-size
Table 8-4 describes the ambit of the bandwidth command.
Table 8-4 Bandwidth Command Parameters
Parameter Description
Interzone Absolute bulk of bandwidth for H.323 cartage from a area to any other
zone.
Total Absolute bulk of bandwidth for H.323 cartage accustomed in a zone.
Session Best bandwidth accustomed for a affair in a zone.
Remote Absolute bandwidth for H.323 cartage amid this attendant and any
other gatekeeper.
check-destination Enables the attendant to verify accessible bandwidth assets at a
destination endpoint.
Default Absence amount for all zones.
zone zone-name Specifies a accurate zone.
bandwidth-size Best bandwidth, in kbps.
For interzone, alien and total, the ambit is 1–10,000,000. For session,
the ambit is 1–5000.
Following are Cisco-provided acceptance guidelines for the bandwidth command:
■ To specify best bandwidth for cartage amid one area and any added zone,
use the absence keyword with the interzone keyword.
■ To specify best bandwidth for cartage aural one area or for cartage between
that area and addition area (interzone or intrazone), use the absence keyword with
the absolute keyword.
■ To specify best bandwidth for a distinct affair aural a specific zone, use the
zone keyword with the affair keyword.
■ To specify best bandwidth for a distinct affair aural any zone, use the default
keyword with the affair keyword.
Zone Bandwidth Agreement Example
Figure 8-40 and Archetype 8-24 appearance a sample of a agreement for a gatekeeper.
508 Authorized Self-Study Guide: Cisco Articulation over IP (CVOICE)
Figure 8-40 Area Bandwidth Agreement Topology
Example 8-24 Area Bandwidth Agreement Example
Chapter 8: Configuring H.323 Gatekeepers 509
IP WAN
PSTN
Router1
(MGCP)
Zone SanJose Area Chicago
Gatekeeper
Phone1-1
2001
Phone2-1
3001
Phone1-2
2002
Phone2-2
3002
Router2
(H.323)
GK1
V V
GK1(config)#gatekeeper
GK1(config-gk)#zone bounded SanJose cisco.com 192.168.1.15
GK1(config-gk)#zone bounded Chicago cisco.com
GK1(config-gk)#zone prefix SanJose 2... gw-priority 10 ICT_CM_1
GK1(config-gk)#zone prefix SanJose 2... gw-priority 9 ICT_CM_2
GK1(config-gk)#zone prefix Chicago 3... gw-priority 10 CME
GK1(config-gk)#gw-type-prefix 1#* default-technology
GK1(config-gk)#bandwidth interzone area SanJose 384
GK1(config-gk)#bandwidth interzone area Chicago 256
GK1(config-gk)#no shutdown
There are two bounded zones: SanJose and Chicago. Notice that the bandwidth interzone
commands are highlighted. In the bandwidth command, the interzone advantage specifies
the bandwidth from one area to addition zone. The aboriginal bandwidth command allocates
384 kbps of bandwidth for H.323 cartage amid the SanJose area and any added zone.
The additional bandwidth command allocates 256 kbps of bandwidth for H.323 traffic
between the Chicago area and any added zone.
Verifying Area Bandwidth Operation
Example 8-25 shows the achievement of the appearance attendant area cachet command. In the
bandwidth advice output, you can see the best interzone bandwidth for all
calls in the SanJose zone. In this scenario, a bandwidth of 384 kbps is configured.
Example 8-25 Verifying Area Bandwidth Operation
510 Authorized Self-Study Guide: Cisco Articulation over IP (CVOICE)
Router#show attendant area status
GATEKEEPER ZONES
================
GK name Domain Name RAS Address PORT FLAGS
------- ----------- ----------- ----- -----
SanJose cisco.com 192.168.1.15 1719 LS
BANDWIDTH INFORMATION (kbps) :
Maximum absolute bandwidth : unlimited
Current absolute bandwidth : 0
Maximum interzone bandwidth : 384
Current interzone bandwidth : 0
Maximum affair bandwidth : unlimited
SUBNET ATTRIBUTES :
All Added Subnets : (Enabled)