Nortel Networks OPTera Metro 3500 - Manual (Page 138)

2-100 Operation, administration, and maintenance (OAM) features
OPTera Metro 3500 Multiservice Platform NTRN10AN Rel 12.1 Standard Iss 1 Apr 2004
In GFP-T, client signals are decoded and mapped into GFP-T frames; these
frames can be transmitted immediately without waiting for the reception of an
entire client data frame. In GFP-F and GFP-T, idle frames are inserted as
necessary to fill the transport payload. Multiple GFP-F frames can be
aggregated in a single SONET payload.
Figure 2-40 on page 2-100 shows how GFP encapsulation is executed for
Transparent and Frame-mapped GFP.
Figure 2-40
GFP Encapsulation
OM1958p
The OPTera Metro 3500 also supports Virtual Concatenation (ITU-T G.707
compliant) with support at the STS-1-nv and STS-3c-nv SONET rates. Up to
14ms of differential delay is supported between each VCAT path.
8B/10B
decode
Client input
Client
PM
T-GFP
encode
VCAT/
CCAT
mapper
VCAT/
CCAT
mapper
GFP
demap
64B/65B
demap
8B/10B
encode
To
client
Virtual
conca-
tenation
STS-x-nv
SONET/SDH
GFP Core Header
Transparent GFP
Used for clients where the inter-frame
gaps contain important client-specific
information e.g. signalling information,
flow control characters Fibre Channel,
ESCON
GFP - FCS
Super blocks that consist of 8
64B/65B blocks and an
error-correcting CRC
- all client data encapsulated
PCS
decode
Client input
Client PM
GMAC F-GFP
encode
GFP
demap
Replace
necessary
inter-frame
bytes
8B/10B
encode
To
client
Virtual
conca-
tenation
STS-x-nv
SONET/
SDH
GFP Core Header
Framed GFP
Used for packet-oriented clients
- no flow control or signalling
characters between packets
Ethernet MAC frames, IP
GFP - FCS
GFP payload area comprising
only client frames - not
inter-frame bytes (Octet aligned)