RFC 1598 (rfc1598) - Page 1 of 7
PPP in X
Alternative Format: Original Text Document
Network Working Group W. Simpson
Request for Comments: 1598 Daydreamer
Category: Standards Track March 1994
PPP in X.25
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Abstract
The Point-to-Point Protocol (PPP) [1] provides a standard method for
transporting multi-protocol datagrams over point-to-point links.
This document describes the use of X.25 for framing PPP encapsulated
packets.
This document is the product of the Point-to-Point Protocol Working
Group of the Internet Engineering Task Force (IETF). Comments should
be submitted to the mailing list.
Applicability
This specification is intended for those implementations which desire
to use facilities which are defined for PPP, such as the Link Control
Protocol, Network-layer Control Protocols, authentication, and
compression. These capabilities require a point-to-point
relationship between peers, and are not designed for multi-point or
multi-access environments.
Simpson [Page i]
RFC 1598 PPP in X.25 March 1994
Table of Contents
1. Introduction .......................................... 1
2. Physical Layer Requirements ........................... 2
3. The Data Link Layer ................................... 2
3.1 Frame Format .................................... 3
3.2 Modification of the Basic Frame ................. 3
4. Call Setup ............................................ 4
5. Configuration Details ................................. 5
SECURITY CONSIDERATIONS ...................................... 6
REFERENCES ................................................... 6
ACKNOWLEDGEMENTS ............................................. 6
CHAIR'S ADDRESS .............................................. 7
AUTHOR'S ADDRESS ............................................. 7
1. Introduction
CCITT recommendation X.25 [2] describes a network layer protocol
providing error-free, sequenced, flow controlled, virtual circuits.
X.25 includes a data link layer, X.25 LAPB, which uses ISO 3309, 4335
and 6256.
PPP also uses ISO 3309 HDLC as a basis for its framing [3].
When X.25 is configured as a point-to-point circuit, PPP can use X.25
as a framing mechanism, ignoring its other features. This is
equivalent to the technique used to carry SNAP headers over X.25 [4].
At one time, it had been hoped that PPP HDLC frames and X.25 frames
would co-exist on the same links. Equipment could gradually be
converted to PPP. Subsequently, it has been learned that some
switches actually remove the X.25 header, transport packets to
another switch using a different protocol such as Frame Relay, and
reconstruct the X.25 header at the final hop. Co-existance and
gradual migration are precluded.
Simpson