Cisco 15327 - Manual (Page 338)

20-6
Ethernet Card Software Feature and Configuration Guide, R7.2
Chapter 20 POS on ONS Ethernet Cards
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 illustrates BCP.
Figure 20-4 BCP Under HDLC Framing
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.
Figure 20-5 illustrates
PPP.
Figure 20-5 PPP Frame Under HDLC Framing
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 illustrates Cisco HDLC.
Figure 20-6 Cisco HDLC Under HDLC Framing
115434
Addr Flag
1 byte
Control Protocol
1 byte 1 byte 2 bytes
Ln/Etype Data/Pad FCS SA DA SFD Preamble
4 bytes 1 byte 7 bytes 46-1500 bytes* 6 bytes 6 bytes 2 bytes
Payload CRC
0x7E
Flag
1 byte
0x7E
2-4 bytes
0xFF 0x03 0x0031 00Z0
Type
0x01
115435
Addr Flag
1 byte
Control Protocol
1 byte 1 byte 2 bytes
IP Packet
Payload CRC
0x7E
Flag
1 byte
0x7E
2-4 bytes
0xFF 0x03 0x0021
Proprietary
115436
Addr Flag
1 byte
Control Protocol
1 byte 1 byte 2 bytes
Ln/EType Data/Pad FCS SA DA SFD Preamble
4 bytes 1 byte 7 bytes 6 bytes 2 bytes
Payload CRC
0x7E
Flag
1 byte
0x7E 0x0F 0x00/8F 0x6558
46-1500 bytes 6 bytes
24 bytes