Nortel Networks 3500, NTRN10AN manual Virtual Concatenation Vcat, Efficiency Rate

Operation, administration, and maintenance (OAM) features 2-101

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)	850 Mbit/s	STS-24c	69%	STS-3c-6v	95%
See Note
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).

Planning and Ordering Guide—Part 1 of 2 NTRN10AN Rel 12.1 Standard Iss 1 Apr 2004