A quick protocol question.

Is a PPP frame size static or elastic? RFC 1661 states:

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 maximum length for the Information field, including Padding, but not including the Protocol field, is termed the Maximum Receive Unit (MRU), which defaults to 1500 octets. By negotiation, consenting PPP implementations may use other values for the MRU.

Padding

On transmission, the Information field MAY be padded with an arbitrary number of octets up to the MRU. It is the responsibility of each protocol to distinguish padding octets from real information.

This is somewhat ambiguous. If I read it straight it sounds like PPP

More to the point is that the frame size is negotiated while handshaking. Once two devices agree on the size it is fixed for the duration of the session. Chris MacFarlane Manager, Data Operations ACC Telenterprises Canada 4162132023 cmacfarlane@acc.ca cjm@ican.net -----Original Message----- From: George Janosik <gjanosik@torrentnet.com> To: nanog@merit.edu <nanog@merit.edu> Date: Wednesday, December 10, 1997 4:09 PM Subject: PPP Question frames

are static and that padding is used to maintain the MRU between endpoints.

But, it also says the the Information field "MAY" be padded up to the MRU.

I have hard time believing that a PPP frame would be static. Very truly yours,

George J Janosik Senior Systems Engineer Torrent Networking Technologies gjanosik@torrentnet.com

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