Nortel Networks OPTera Metro 3500 - Manual (Page 139)

Operation, administration, and maintenance (OAM) features 2-101
Planning and Ordering Guide—Part 1 of 2 NTRN10AN Rel 12.1 Standard Iss 1 Apr 2004
The OPTera Metro 3500 2xGigE/FC-P2P circuit pack maps Gigabit Ethernet
client signals via GFP-F frames and maps FC100/FICON clients signals via
GFP-T frames.
Virtual Concatenation (VCAT)
Virtual Concatenation (VCAT) is not a new transport protocol but a provision
in existing ITU-T standards (G.707 & G.783) and ANSI standards (T1.105).
Although is has not been widely adopted as mainstream networking
technology, the protocol enables a more efficient support of packet data
services through a more efficient use of the traditional coarse concatenation
SONET TDM bandwidth. VCAT enables the operator to take existing SONET
provisioning paths and map the new packet data service into an arbitrary
number of STS-1 or STS-3c units within these paths. The transport capacity is
therefore decoupled from the service bandwidth, resulting in less stranded
bandwidth for a given link.
VCAT services are available in different virtual containers:
• STS-1-nv, where n is 1 through 21
• STS-3c-nv, where n is 1 through 7
VCAT provides an efficient transport of data-oriented services, by grouping a
number (n) of virtual container (STS-1/3c SPEs), by using the combined
payload (STS-x-nv) to match the required bandwidth.
Table 2-21 on page
2-101 , highlights the efficient network resource utilization achieved with
VCAT.
Table 2-21
Contiguous versus virtual concatenation efficiency
Service Client Rate Contiguous Concatenation Virtual Concatenation
Rate Efficiency Rate Efficiency
Fibre Channel (FC-100)
See
Note
850 Mbit/s STS-24c 69% STS-3c-6v 95%
Gigabit Ethernet 1 Gbit/s STS-24c 81% STS-1-21v 95%
STS-48c 42% STS-3c-7v 95%
Note: When connected to a pair of Fibre Channel devices that support the autonegotiation (AN) of 1G
and 2G link speeds, the speed of the ports connected to the 2xGigE/FC -P2P card must be manually
set to 1G (FC-100).