RFC 1618 (rfc1618) - Page 1 of 6
PPP over ISDN
Alternative Format: Original Text Document
Network Working Group W. Simpson
Request for Comments: 1618 Daydreamer
Category: Standards Track May 1994
PPP over ISDN
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 PPP over Integrated Services
Digital Network (ISDN) switched circuits.
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 the PPP encapsulation over ISDN point-to-point links. PPP is
not designed for multi-point or multi-access environments.
"It is clear that there is never likely to be a single, monolithic,
worldwide ISDN." [3] The goal of this document is to describe a few
common implementations, chosen from the current wide variety of
alternatives, in an effort to promote interoperability.
Simpson [Page i]
RFC 1618 PPP over ISDN May 1994
Table of Contents
1. Introduction .......................................... 1
2. Physical Layer Requirements ........................... 1
3. Framing ............................................... 3
4. Out-of-Band signaling ................................. 4
5. Configuration Details ................................. 5
SECURITY CONSIDERATIONS ...................................... 5
REFERENCES ................................................... 5
ACKNOWLEDGEMENTS ............................................. 6
CHAIR'S ADDRESS .............................................. 6
AUTHOR'S ADDRESS ............................................. 6
Simpson [Page ii]
RFC 1618 PPP over ISDN May 1994
1. Introduction
PPP was designed as a standard method of communicating over point-
to-point links. Initial deployment has been over short local lines,
leased lines, and plain-old-telephone-service (POTS) using modems.
As new packet services and higher speed lines are introduced, PPP is
easily deployed in these environments as well.
This specification is primarily concerned with the use of the PPP
encapsulation over ISDN links. Since the ISDN B-channel is by
definition a point-to-point circuit, PPP is well suited to use over
these links.
The ISDN Primary Rate Interface (PRI) may support many concurrent B-
channel links. The PPP LCP and NCP mechanisms are particularly
useful in this situation in reducing or eliminating hand
configuration, and facilitating ease of communication between diverse
implementations.
The ISDN D-channel can also be used for sending PPP packets when
suitably framed, but is limited in bandwidth and often restricts
communication links to a local switch.
The terminology of ISDN can be confusing. Here is a simple graphical
representation of the points used in subsequent descriptions:
+-------+ +-------+ +-------+
R | | S | | T | | U
+---+ TA +--+--+ NT2 +--+--+ NT1 +---+
| | | | | |
+-------+ +-------+ +-------+
These elements are frequently combined into a single device.
2. Physical Layer Requirements
PPP treats ISDN channels as bit or octet oriented synchronous links.
These links MUST be full-duplex, but MAY be either dedicated or
circuit-switched.
Interface Format
PPP presents an octet interface to the physical layer. There is
no provision for sub-octets to be supplied or accepted. The octet
stream is applied primarily at the R or T reference points.
Simpson
