Ppp/Bcp; Cisco Hdlc; Figure 20-4 Bcp Under Hdlc Framing; Figure 20-5 Ppp Frame Under Hdlc Framing - Cisco ONS 15454 SDH Configuration Manual

PPP/BCP

PPP/BCP
The PPP encapsulation is a standard implementation of RFC 2615 (PPP-over-SONET/SDH), and
provides a standard implementation of RFC 3518 (BCP) to provide the transmission of 802.1Q tagged
and untagged Ethernet frames over SONET.
Figure 20-4 BCP Under HDLC Framing
1 byte 1 byte 1 byte 2 bytes
Flag Addr Control Protocol
0x7E 0xFF 0x03 0x0031 00Z0
In some framing modes, the ONS 15454/ONS 15454 SDH ML-Series card supports routing functions.
When this card POS port is configured to support routing with the PPP encapsulation, the IP packets are
mapped into the HDLC frames that use the standard 0x0021 protocol code point.
PPP.
Figure 20-5 PPP Frame Under HDLC Framing
1 byte 1 byte 1 byte
Flag Addr Control
0x7E 0xFF 0x03

Cisco HDLC

Cisco HDLC is a Cisco-standard mapping of packets into a serial interface. This encapsulation can be
used to connect the interface on an ML-Series card to a POS interface on Cisco HDLC-compliant routers
and switches.
When used to carry IP packets, the same HDLC frame structure is used, however the protocol field is set
to 0x0800, and the payload contains the IP packet.
Figure 20-6 Cisco HDLC Under HDLC Framing
1 byte 1 byte 1 byte
Flag Addr Control Protocol
0x6558
0x7E 0x0F 0x00/8F
7 bytes
Preamble
Cisco ONS 15454 and Cisco ONS 15454 SDH Ethernet Card Software Feature and Configuration Guide, R8.0
20-6
Type
0x01
7 bytes 1 byte 6 bytes 6 bytes 2 bytes
Preamble SFD DA
2 bytes
Protocol
0x0021
Proprietary
2 bytes
1 byte 6 bytes 6 bytes 2 bytes
SFD DA SA Ln/EType
Figure 20-4 illustrates BCP.
Payload
46-1500 bytes*
SA Ln/Etype Data/Pad
Payload
IP Packet
Figure 20-6
Payload
46-1500 bytes
Data/Pad
Chapter 20 POS on ONS Ethernet Cards
2-4 bytes 1 byte
CRC Flag
0x7E
4 bytes
FCS
Figure 20-5
2-4 bytes 1 byte
CRC Flag
0x7E
illustrates Cisco HDLC.
24 bytes 1 byte
CRC Flag
0x7E
4 bytes
FCS
illustrates