Encapsulation; Layer 2 And Layer 3 Traffic Management - Alcatel-Lucent 7705 Service Manual

At the remote SR end, the SAP is bound to a VPRN instance to ensure that LDP signaling to
the system IP address of the 7705 SAR flows through the IP/GRE link and not over the
ATM link. Within the VPRN, an IP address is assigned at the termination SAP. The IP
datagram is extracted from the ATM cell at this termination point and is routed to the
5620 SAM.
Alternatively, manually configured connections can be used instead of signaled
pseudowires.
Note: The remote IP address must be manually configured and a static route must be set up
between the two connections. This configuration is beyond the scope of this document; refer
to the 7705 SAR OS Router Configuration Guide for information.
For redundancy, it is recommended that two VCs be configured per ATM port or IMA
group. This requires the configuration of two static routes. ECMP must be enabled to allow
duplicate routes in the routing table, and BFD can be enabled to trigger a faster handoff to
the other route in case of route failure.

Encapsulation

To run IP traffic over ATM links, the system uses routed VC-mux encapsulation as specified
in RFC 2684, Multiprotocol Encapsulation over ATM Adaptation Layer 5. Since the only
supported Layer 3 protocol over the management VC is IP, the VC mux encapsulation
method is implemented to reduce complexity and overhead; likewise, routing mode is
preferred over bridged mode.
The maximum MTU size supported is 2048 bytes.

Layer 2 and Layer 3 Traffic Management

ATM traffic descriptors can be applied at the ingress (policing) and egress (shaping and
service category scheduling and prioritization) of the IES SAP in order to provide traffic
management functions at Layer 2.
Management IP traffic that is destined for the CSM is classified at Layer 3 and is forwarded
into the fabric from one of three of the adapter card control queues:
7705 SAR OS Services Guide
• high priority
• low priority
• FTP priority
Internet Enhanced Service
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