Alcatel-Lucent 7705 Interface Configuration Manual page 34

Port Features
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 0x003d 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 options used during the LCP state for creating an MLPPP NCP session are
described below.
B&E Bits
The B&E bits are used to indicate the start and end of a packet. Ingress packets to the
MLPPP process will have an MTU, which may or may not be larger than the maximum
received reconstructed unit (MRRU) of the MLPPP network. The B&E bits manage the
fragmentation of ingress packets when the packet exceeds the MRRU.
The B-bit indicates the first (or beginning) packet of a given fragment. The E-bit indicates
the last (or ending) packet of a fragment. If there is no fragmentation of the ingress packet,
both B&E bits are set to true (=1).
Sequence Number
Sequence numbers can be either 12 or 24 bits long. The sequence number is 0 for the first
fragment on a newly constructed bundle and increments by one for each fragment sent on
that bundle. The receiver keeps track of the incoming sequence numbers on each link in a
bundle and reconstructs the desired unbundled flow through processing of the received
sequence numbers and B&E bits. For a detailed description of the algorithm, refer to
RFC 1990.
Information Field
The Information field is zero or more octets. The Information field contains the datagram for
the protocol specified in the protocol field.
The MRRU will have the same default value as the MTU for PPP. The MRRU is always
negotiated during LCP.
Page 34 7705 SAR OS Interface Configuration Guide