Versatile Service Module (Vsm) - Alcatel-Lucent 7750 SR OS Interface Configuration Manual

Configuration Overview

Versatile Service Module (VSM)

The Versatile Service Module (VSM) is a module that allows operators to internally connect a
VPLS or VLL service into an IES or IPVPN service. Each module is capable of 10 Gbps
throughput.
This module is provisioned as a Cross Connect Adaptor (CCA). Unlike external port connections
which utilize two TX-RX paths, a CCA interconnects the egress forwarding path on the IOM
directly to the ingress forwarding path. This eliminates the need for the physical port MAC, PHY,
cable and other MDA-specific components producing a less costly and more reliable adaptor. The
complete 10G+ forwarding path is available allowing single conversations up to 10G.
Bandwidth is utilized in a more efficient manner than with externally cabled ports. Typically, the
offered load presented to each side of the cross connect port pair is asymmetric in nature. When
physical ports are used to cross connect services, each service is egress bandwidth limited to the
link speed of the TX-RX path it is using. If one TX-RX path is under utilized, egress services on
the other path cannot make use of the available bandwidth.
Since the CCA is forwarding all services over the same path, all the available bandwidth may be
used. An example of this would be a two services connected over a CCA. Service A is a VPLS.
Service B is an IES. There are two directions of traffic between the pair, A to B and B to A. Traffic
in both directions travels across the CCA in the same path. The total bandwidth the CCA can
forward is 10 Gbps. Therefore, A to B could consume 7 Gbps, and B to A could consume 3 Gbps.
Any combination of services and traffic directions adding up to 10 Gbps can be supported on a
single CCA.
The forwarding plane the CCA interconnects maintains the complete egress and ingress features of
the services it is interconnecting. This includes the ability to remap QoS, enforce policing and
shaping and provide ingress and egress accounting for each service.
In addition CCAs may be placed into Cross Connect Aggregation Groups (CCAGs). A CCAG
provides a mechanism to aggregate multiple CCAs into a single forwarding group.
The CCAG uses conversation hashing to dynamically distribute cross connect traffic to the active
CCAs in the aggregation group. In the event that an active CCA fails or is removed from the
group, the conversation hashing function will redistribute the traffic over the remaining active
CCAs within the group. The conversation hashing mechanism performed for a CCAG is identical
to the hashing functions performed for Ethernet LAGs (Link Aggregation Groups).
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