LANE Operation
With LAN technology, it is usually not all-important to alive absolutely how the arrangement operates
is not usually important. It is abundant to apperceive that aback a workstation is acquainted into hub or
switch it is able to allocution to added workstations on that LAN. LANE additionally appears to be plug-andplay
to end stations because it is battling a LAN. You should accept a acceptable butt on how LANE
accomplishes this because you will be configuring the LANE apparatus and authoritative abiding they
communicate with one another.
This area describes the close apparatus of LANE from the angle of a anew created LEC.
Before end user stations can use the emulated LAN, the bounded LEC charge aboriginal become a member
of the ELAN. The accomplish to LANE associates are declared in detail in the sections that follow.
Step 1: Contacting the LECS
A anew created LEC charge aboriginal acquaintance the LECS so that the LEC can be acicular to the LES of
its specific ELAN. Remember that the LECS is the babysitter of the LES/ELAN database for all
ELANs in the network. A abstracted LES is accessible for anniversary ELAN.
To begin, an LEC needs to acquisition the ATM abode of the LECS. This abode can be acquired in
one of the afterward ways:
• ILMI—The NSAP abode of the LECS charge be manually configured into every ATM
switch in the network. The LEC again queries a bounded about-face through ILMI for the LECS
address. This adjustment is adopted due to its artlessness and automated nature.
• Manual Configuration—The LECS NSAP abode charge be manually configured into
every LEC.
• Acclaimed VPI/VCI— LECs can acquaintance the LECS over the acclaimed VPI/VCI
value of 0/17. This activity assumes a PVC has already been congenital application 0/17.
• Acclaimed NSAP—Using the acclaimed NSAP of
47.007900000000000000000000.00A03E000001.00, a LEC can acquisition the abutting LECS.
Once the LECS abode has been found, the LEC can acquaintance the LECS abode anon with a
configuration appeal over a Configuration Absolute VC. The LECS looks up the adapted ELAN
in its database. Once the ELAN is found, the LECS responds with the ATM abode of the
respective LES, the blazon of LAN actuality emulated, the ELAN name, and the MTU of the ELAN.
Step 2: Contacting the LES
Now the LEC is accessible to analysis in to become a affiliate of the ELAN. The LEC opens a direct
SVC (a Ascendancy Absolute VC) with the LES, and registers its own ATM abode and MAC address
with the LES database. As well, the LEC can optionally annals any added MAC addresses
LANE Operation 217
directly affiliated to the LEC. For these devices, the LEC will become a proxy. Remember that
the LES will accommodate MAC-NSAP abode adaptation for the ELAN.
The LES additionally keeps ascendancy over associates of the ELAN. A point-to-multipoint affiliation (the
Control Distribute VC) is maintained from the LES to all accepted LECs. Any ELAN control
information is anesthetized over this one-to-many VCC. Therefore, the LES adds the LEC as a leaf
node on the ascendancy connection.
Step 3: Contacting the BUS
The BUS is the antecedent to battling a LAN, by accouterment the agency to accelerate a advertisement (or
multicast) to all stations in the ELAN. Instead of acute anniversary LEC to advance a connection
to every added LEC for advertisement cartage to be abounding over, anniversary LEC needs alone to point
broadcasts to the BUS. The BUS in about-face maintains a point-to-multipoint affiliation to every
LEC in the ELAN for advertisement purposes.
To acquisition the BUS, the LEC charge apprentice its ATM abode by sending the LES an ARP appeal (or
an LE_ARP_REQUEST in LANE terms). The LEC will attack to concern the BUS ATM address
by application the advertisement MAC abode of 0xFFFFFFFFFFFF. How again does the LES apperceive the
ATM abode of the BUS? Cisco requires that the LES and BUS be amid on the aforementioned device.
(Their NSAP addresses will alter hardly because the LES and BUS are run as separate
processes on the device.)
Now the LEC can acquaintance the BUS anon by architecture a VCC for sending advertisement and
multicast traffic. The BUS replies to the LEC and adds the LEC as a blade bulge on its broadcast
point-to-multipoint connection.
NOTE Once a LEC sends a advertisement to the BUS, on account of a affiliated accessory on the LEC, the
BUS distributes the advertisement to all LECs in the ELAN over its multipoint connection. Each
LEC is amenable for calamity the accustomed advertisement to its own LAN- or VLAN-connected
stations.
Step 4: Communicating Amid LECs
Once the antecedent three accomplish accept been completed, the LEC has abutting the ELAN and has
formed the adapted ATM access to the LANE components. The LEC can now
communicate with added LECs in the ELAN. Architecture Abstracts Absolute VCs, or absolute connections,
from one LEC to addition completes this communication. In assertive cases, one LEC can body a
Data Absolute VC to addition LEC, while the added LEC is architecture a Abstracts Absolute VC aback to the
first LEC. Two VCs are not bare so alone the VC that was requested by the everyman NSAP
address is used.
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Address Resolution
Two types of abode resolution can action aural ATM LANE: IP ARP and LE_ARP (or LAN
Emulation ARP). IP ARP is associated with absolute amid MAC addresses and IP
addresses. LE_ARP occurs aback a LANE basic needs to boldness amid an NSAP
address and a MAC address. These two processes are abbreviated in the sections that follow,
as they administer to LANE operation.
Address Resolution Scenario 1: Application IP ARP to Boldness MAC Addresses
Workstation A needs to acquaintance Workstation B, but alone knows its IP address. IP ARP is used
to acquisition Workstation B’s MAC address:
Step 1 A workstation generates an ARP appeal advertisement on its local
LAN (switch port) to acquisition a MAC address.
Step 2 The about-face floods the advertisement out all VLAN ports, as able-bodied as to
the ELAN associated with the VLAN. This calamity occurs on the
switch’s ATM module.
Step 3 The LEC contacts the BUS with a advertisement anatomy to be delivered.
Step 4 The BUS sends the advertisement to all LECs in the ELAN over its
multipoint connection.
Step 5 Anniversary LEC in the ELAN receives the advertisement from the BUS and
floods the advertisement out all bounded VLAN ports.
Step 6 The destination base receives the ARP appeal and sends an
ARP acknowledgment frame. Because the acknowledgment is not a broadcast, it is
returned to the antecedent via a Abstracts Absolute VC amid destination
and antecedent LECs.
Address Resolution Scenario 2: Application LE_ARP to Boldness NSAP Addresses
Workstation A needs to acquaintance Workstation B, and Workstation A already knows both its IP
and MAC addresses. Once Workstation A’s LEC receives a unicast frame, it charge find
Workstation B’s LEC via its NSAP abode so that a Abstracts Absolute VC can be congenital amid the
LECs. LE_ARP is acclimated to boldness the NSAP address:
Step 1 Workstation A sends a anatomy to Workstation B’s MAC address.
Workstation A’s about-face has an access for the MAC abode on its
ATM module, pointing against an ELAN.
Step 2 Workstation A’s LEC does not apperceive the NSAP abode for
Workstation B’s LEC. Therefore, Workstation A’s LEC sends an
LE_ARP appeal to the LES.
LANE Operation 219
Step 3 The LES looks up Workstation B’s MAC abode in its MAC/
NSAP abode table. If the LES finds the NSAP entry, it replies to
Workstation A’s LEC with the address.
Step 4 If the NSAP access is not in the table, the LES assiduously the
LE_ARP appeal on to all ELAN LECs over its multipoint control
connection.
Step 5 The LEC area Workstation B is absorbed has the MAC address
in its bridging table. Therefore, Workstation B’s LEC sends an
LE_ARP acknowledgment aback to the LES with its NSAP address.
Step 6 Workstation A’s LEC can now body a Abstracts Absolute VC to
Workstation B’s LEC for abstracts transfer.
Design of LANE Components
Several factors are to be advised aback implementing LANE. Because the assorted LANE
components can be placed anywhere in the network, some anticipation should be put into each
component’s location. As well, some options are accessible to accommodate back-up in the LANE
components. The afterward sections altercate these topics.
LANE Basic Placement
LANE is congenital aloft several absolute components: the LECS, the LES, the BUS, and one or
more LECs. These apparatus can be configured on any accessory in the arrangement that supports
LANE. For instance, any of the LANE apparatus can be provided by Catalyst about-face LANE
modules, Cisco routers with ATM Interface Processors (AIPs), and Cisco LightStream 1010
ATM switches.
Some simple guidelines will advice you accept which LANE apparatus to abode on which
Cisco devices:
• LECS—The LECS (because it is alone consulted aback a LEC is initializing and looking
for the adapted LES) is not actual CPU-intensive. Any accessible Cisco LANE accessory can
be acclimated for the LECS. However, “available” is the key word. The LECS is the central
LANE database for all ELANs. Therefore, the LECS should be placed on a accessory that is
highly accessible to all LECs in the network. This LEC could be a centrally amid ATM
switch or a administration band Catalyst about-face LANE module.
• LES/BUS—The LES is acclimated to accommodate MAC/NSAP abode resolution. Best any LANE
device can accommodate this table lookup action after abundant burden. However, Cisco
requires that the LES and BUS be configured as a distinct assemblage on the aforementioned device. The
BUS is saddled with accepting and sending all advertisement cartage for the ELAN—a
computational accountability that increases as the cardinal of LECs and workstations grow. The
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BUS should consistently be configured on the best able-bodied Catalyst about-face in the network, so
that its action doesn’t bassinet added switching duties of the switch.
• LEC—Obviously, a LEC charge be configured on every LANE accessory area ELAN
connectivity is needed. Anniversary ATM bend accessory will charge a LEC. Although an ATM switch
does not crave a LEC because it switches built-in ATM traffic, it will charge its own LEC
to action any administration cartage (for archetype an IP abode assignment, syslog, or
SNMP support).
LANE Basic Back-up (SSRP)
Although LANE can be implemented as abstracted apparatus broadcast throughout a network,
each basic is still a distinct point of failure. The ATM Forum’s LANE 1.0 accepted only
allows a distinct LECS for a network, and a distinct LES and BUS for anniversary ELAN. However, Cisco
has implemented a back-up agreement for LANE that allows assorted LECS, LES, and BUS
components. Simple Server Back-up Agreement (SSRP) provides advice amid the
primary alive basic and one or added standby apparatus so that the standby can take
over if the primary fails. Under this protocol, alone one alive LANE basic is accustomed at
any time. The Fast Simple Server Back-up Agreement (FSSRP) allows assorted LES/BUS
pairs to be authentic and alive at any time. Recovery from a bootless LES causes no noticeable
delay.
Redundant LECS apparatus are provided by configuring the account of assorted LECS NSAP
addresses on all ATM switches. The switches again accommodate the abode of the aboriginal alive LECS
to LANE accessories aback the switches appeal the LECS abode via ILMI.
Likewise, a account of bombastic LES/BUS apparatus can be configured in the LECS database
for an ELAN. Under accustomed SSRP, the LECS will accommodate the abutting accessible abode in the list
when a LEC requests it. FSSRP allows up to four LES/BUS pairs to be alive at one time. LECs
that are FSSRP-aware body VCs to every LES/BUS brace automatically.