25-7
Ethernet Card Software Feature and Configuration Guide, R7.2
January 2009
Chapter 25 CE-1000-4 Ethernet Operation
CE-1000-4 POS Encapsulation, Framing, and CRC
• Add or remove cross-connect circuits from VCGs
• Automatically remove errored members from the group
Adding or removing members from the VCG is service-affecting. Adding or removing cross-connect
circuits is not service-affecting, if the asociated members are not in the group
The CE-1000-4 card also supports fixed (pure or non-flexible) VCGs. With non-flexible VCGs, the
CE-1000-4 is more limited an can only perform these operations:
• Put members into or out of service
• Add or remove cross-connect circuits associated with members
With non-flexible VCGs, the limitations of the CE-1000-4 include:
• Cannot add or remove members from groups
• Cannot automatically remove errored members from the group
The CE-1000-4 card allows independent routing and protection preference s for each member of a VCAT
circuit. The user can also control the amount of VCAT circuit capacity that is fully protected,
unprotected, or uses Protection Channel Access (PCA) (when PCA is available). Alarms are supported
on a per-member as well as per virtual concatenation group (VCG) basis.
The CE-1000-4 card supports VCAT common fiber routing and VCAT split fiber (diverse) routing.
Common fiber routing is compatible with two-fiber bidirectional line switched ring ( BLSR) protection
schemes and APS. It does not support path protection and four-fiber BLSR protection schemes. Split
fiber routing supports all protection types: path protection, two-fiber BLSR, four-fiber BLSR, and linear
switching (1+1).
With VCAT split fiber routing, each member can be routed independently through the SONET/SDH
network instead of having to follow the same path as required by CCAT and VCAT common fiber
routing. This allows a more efficient use of network bandwidth, but the different path lengths and
different delays encountered may cause slightly different arrival times for the individual m embers of the
VCG. The VCAT differential delay is this relative arrival time measurement between members of a
VCG. The maximum tolerable VCAT split fiber routing differential delay for the CE-1000-4 card is
approximately 120 milliseconds. A loss of alignment alarm is generated if the maximum differential
delay supported is exceeded.
The differential delay compensation function is automatically enabled when the user chooses split fiber
routing during the CTC circuit configuration process. CCAT and VCAT common fiber routing do not
enable or need differential delay support.
Caution Protection switches of less than 60ms are not guarante ed with the differential delay compensation
function enabled. The compensation time is added to the switching time.
Note For TL-1, EXPBUFFERS parameter must be set to ON in the ENT-VCG to enable support for split fiber
routing.
CE-1000-4 POS Encapsulation, Framing, and CRC
The CE-1000-4 card uses Cisco EoS LEX (LEX). LEX is the primary encapsulation of ONS Ethernet
cards. In this proprietary HDLC-based encapsulation, the protocol field is set to the values specified in
Internet Engineering Task Force (IETF) Request For Comments (RFC) 1841.