Technical data

TraverseEdge 2020 Applications and Engineering Guide, Chapter 3: System Applications
Page 3-58 Turin Networks Release 5.0.x
Figure 3-51 illustrates the VC mapping for an STS-3c-7v GbE connaction. Each of the STS paths in an
STS-Nc-Xv connection carries its own Path OverHead (POH). This allows the SONET network to treat
these paths just as it treats other STS-3c or STS-1paths. For example, the STS paths in an STS-3c-7v con-
nection:
• May occupy non-contiguous time slots, although each STS-3c time slot must fall on standard
STS-3c boundaries (e.g., STS #1-3, 4-6, 10-12, 22-24)
• May, in a UPSR configuration, be independently path-switched
• May take different routes through the SONET network, although all seven STS-3c paths must
terminate at a common end point, which performs the virtual concatenation egress functions.
In the egress direction, the GbE PLM recombines the seven STS-3c or STS-1 path payloads into a contigu-
ous octet stream. The information in the H4 byte of the POH of each STS-3c or STS-1 creates a multiframe
structure, which allows the GbE PLM to determine the order in which it should extract octets from the
STS-3c or STS-1 payloads (i.e., which STS-3c or STS-1 to read first, which to read second, etc.) and to
compensate for differential delay.
The GbE must compensate for differential delay, since each of the STS-3c or STS-1 paths may take a dif-
ferent route through the network, and some paths may therefore arrive at the destination GbE PLM before
others. In order to compensate for differential delay, the GbE PLM must buffer the earliest STS-3c or STS-
1 until it receives the latest STS-3c or STS-1. The GbE PLM can compensate for up to 4 ms of differential
delay. This represents the difference between the delays of the longest and shortest paths between the
ingress and egress GbE interfaces, as Figure 3-52 depicts.
Figure 3-52 Differential Delay Illustration
The TE-2020 also supports VC Groups. A VC Group is a logical association of multiple virtually concate-
nated STS subfacilities that allows a user to operate on the group as a whole. A user may, for example,
make a cross-connect between two VC Groups instead of making multiple individual STS cross-connects,