Figure 4: Mlppp 24-Bit Fragment Format; Figure 5: Mlppp 12-Bit Fragment Format - Alcatel-Lucent 7750 Configuration Manual

encapsulation is the same as that used by PPP, and described in PPP in HDLC-like framing [RFC
1662]. MP frames use the same HDLC address and control pair value as PPP, namely: Address -
OxFF and Control - Ox03. The two octet protocol field is also structured the same as in PPP
encapsulation. A summary of the MP encapsulation is shown in
The required and default format for MP is the 24-bit format. During the LCP state the 12-bit
format can be negotiated. The SR-series routers can support and negotiate the alternate 12-bit
frame format.
Protocol Field (PID)
The protocol field is two octets its value identifies the datagram encapsulated in the Information
field of the packet. In the case of MP the PID also identifies the presence of a 4-octet MP header
(or 2-octet, if negotiated).
A PID of Ox003d identifies the packet as MP data with an MP header.
The LCP packets and protocol states of the MLPPP session follow those defined by PPP in RFC
1661, The Point-to-Point Protocol (PPP). The options used during the LCP state for creating an
MLPPP NCP session are described below.
7750 SR Interface Configuration Guide
1 1
0 1 2 3 4 5 6 7 8 9 0 1
Address 0xff Control 0x03
B E
Fragment Data

Figure 4: MLPPP 24-bit Fragment Format

1 1
0 1 2 3 4 5 6 7 8 9 0 1
Address 0xff Control 0x03
B E Sequence
Fragment Data

Figure 5: MLPPP 12-bit Fragment Format

1 1 1 1 1 1 1 1 2 2 2 2
2 3 4 5 6 7 8 9 0 1 2 3
PID 0x003d
Sequence
Fragment Data...
FCS
1 1 1 1 1 1 1 1 2 2 2 2
2 3 4 5 6 7 8 9 0 1 2 3
PID 0x003d
Fragment Data ...
Fragment Data...
FCS
Interface Configuration
Figure 4.
2 2 2 2 2 2 3 3
4 5 6 7 8 9 0 1
2 2 2 2 2 2 3 3
4 5 6 7 8 9 0 1
Page 57