Ethernet Rates And Mapping; Frame Size; Encapsulations; Path And Circuit Sizes - Cisco ONS 15600 Reference Manual

10.3 Ethernet Rates and Mapping

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10.3 Ethernet Rates and Mapping
This section explains the Ethernet frame format, encapsulation methods, path and circuit configurations,
and oversubscription.

10.3.1 Frame Size

The IEEE 802.3 frame format is supported on the GE interfaces. The minimum frame size supported by
the system is 64 bytes; the interface drops smaller sized frames. The maximum frame size per interface
is 9600 bytes and can be provisioned independently. 9600 bytes is the maximum transmission unit
(MTU).

10.3.2 Encapsulations

The Ethernet ports can be provisioned for encapsulation in frame-mapped GFP (GFP-F) as per
ITU G.7041, Cisco HDLC/LEX as per RFC 1841, or Ethernet over Link Access Protocol over SDH
(LAPS) as per ITU X.86. LEX with CRC-32 is the default encapsulation, as it is supported by most Cisco
data cards.
The value of the C2 byte in a high-order SONET path is set to the following values for each
encapsulation type:
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Bridge Control Protocol (BCP), HDLC, LEX, and ITU X.86 are all variations of Point-to-Point Protocol
Note
(PPP) in HDLC framing. To the Ethernet processor, the packets look essentially the same. GFP
encapsulation is drastically different.

10.3.3 Path and Circuit Sizes

GE interfaces can be mapped to all supported SONET paths of sizes STS-1, STS-3c, STS-6c, STS-9c,
STS-12c, STS-24c, and STS-48c.
Note Mapping depends on the particular concatenation being supported on the card. It also depends on the
concatenation being supported on all of the network elements (NEs) that the end-to-end circuit is being
built through.
Cisco ONS 15600 Reference Manual, R8.0
10-4
Valid preamble + synchronization
Valid size
Valid cyclic redundancy check (CRC)
Valid interpacket gap
0x1B for GFP-F
0x18 for X.86
0x05 for LEX with CRC-16
0x01 for LEX with CRC-32
Chapter 10 Ethernet Operation