Network Working Group G. Gross
Request for Comments: 2363 Lucent Technologies
Category: Standards Track M. Kaycee
PPP Over FUNI
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.
Copyright (C) The Internet Society (1998). All Rights Reserved.
The Point-to-Point Protocol (PPP)  provides a standard method for
transporting multi-protocol datagrams over point-to-point links.
This document describes the use of ATM Frame User Network Interface
(FUNI) for framing PPP encapsulated packets.
This specification is intended for those implementations which desire
to use the 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 the peers, and are not designed for the multi-
point relationships which are available in ATM and other multi-access
Gross, et. al. Standards Track [Page 1]RFC 2363 PPP Over FUNI July 19981. Introduction
ATM FUNI protocol is designed to provide virtual connections between
end stations attached to the same network. These connections offer a
packet delivery service that includes error detection, but does not
do error correction.
Most existing implementations of PPP use ISO 3309 HDLC as a basis for
their framing .
When an ATM network is configured with point-to-point connections,
PPP can use FUNI as a framing mechanism.
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
document, are to be interpreted as described in .
3. FUNI Layer Service Interface
The PPP layer treats the underlying ATM FUNI layer service as a bit-
synchronous point-to-point link. In this context, the PPP link
corresponds to an ATM FUNI virtual connection. The virtual
connection MUST be full-duplex, point to point, and it MAY be either
dedicated (i.e. permanent, set up by provisioning) or switched (set
up on demand). In addition, the PPP/FUNI service interface boundary
MUST meet the following requirements:
Interface Format - The PPP/FUNI layer boundary presents an octet
service interface to the FUNI layer. There is no provision for
sub-octets to be supplied or accepted.
Transmission Rate - The PPP layer does not impose any
restrictions regarding transmission rate or the underlying ATM
layer traffic descriptor parameters.
Control Signals - The FUNI layer MUST provide control signals to
the PPP layer which indicate when the virtual connection link
has become connected or disconnected. These provide the "Up"
"Down" events to the LCP state machine  within the PPP layer.
Gross, et. al. Standards Track [Page 2]RFC 2363 PPP Over FUNI July 19984. Multi-Protocol Encapsulation
This specification uses the principles, terminology, and frame
structure described in "Multiprotocol Encapsulation over ATM
Adaptation Layer 5" .
The purpose of this specification is not to document what is already
standardized in , but to specify how the mechanisms described in
 are to be used to map PPP onto a FUNI-based ATM network.
Section 1 within  defines the two mechanisms for identifying the
Protocol Data Unit (PDU) payload field's protocol type: virtual