6.1. Maximum-Receive-Unit (MRU)

Description

This Configuration Option may be sent to inform the peer that the implementation can receive larger packets, or to request that the peer send smaller packets.

The default value is 1500 octets. If smaller packets are requested, an implementation MUST still be able to receive the full 1500 octet information field in case link synchronization is lost.

Implementation Note:

This option is used to indicate an implementation capability. The peer is not required to maximize the use of the capacity. For example, when a MRU is indicated which is 2048 octets, the peer is not required to send any packet with 2048 octets. The peer need not Configure-Nak to indicate that it will only send smaller packets, since the implementation will always require support for at least 1500 octets.

A summary of the Maximum-Receive-Unit Configuration Option format is shown below. The fields are transmitted from left to right.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |      Maximum-Receive-Unit     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Type

1

Length

4

Maximum-Receive-Unit

The Maximum-Receive-Unit field is two octets, and specifies the maximum number of octets in the Information and Padding fields. It does not include the framing, Protocol field, FCS, nor any transparency bits or bytes.