Encapsulation Methods for Transport of PPP/High-Level Data Link Control (HDLC) over MPLS Networks
RFC 4618
Network Working Group L. Martini
Request for Comments: 4618 E. Rosen
Category: Standards Track Cisco Systems, Inc.
G. Heron
A. Malis
Tellabs
September 2006
Encapsulation Methods for Transport of
PPP/High-Level Data Link Control (HDLC) over MPLS Networks
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 Notice
Copyright (C) The Internet Society (2006).
Abstract
A pseudowire (PW) can be used to carry Point to Point Protocol (PPP)
or High-Level Data Link Control (HDLC) Protocol Data Units over a
Multiprotocol Label Switching (MPLS) network without terminating the
PPP/HDLC protocol. This enables service providers to offer
"emulated" HDLC, or PPP link services over existing MPLS networks.
This document specifies the encapsulation of PPP/HDLC Packet Data
Units (PDUs) within a pseudowire.
Martini, et al. Standards Track [Page 1]
RFC 4618 Transport of PPP/HDLC over MPLS September 2006
Table of Contents
1. Introduction ....................................................2
2. Specification of Requirements ...................................2
3. Applicability Statement .........................................5
4. General Encapsulation Method ....................................6
4.1. The Control Word ...........................................6
4.2. MTU Requirements ...........................................8
5. Protocol-Specific Details .......................................9
5.1. HDLC .......................................................9
5.2. Frame Relay Port Mode ......................................9
5.3. PPP .......................................................10
6. Using an MPLS Label as the Demultiplexer Field .................11
6.1. MPLS Shim EXP Bit Values ..................................11
6.2. MPLS Shim S Bit Value .....................................11
7. Congestion Control .............................................12
8. IANA Considerations ............................................12
9. Security Considerations ........................................12
10. Normative References ..........................................13
11. Informative References ........................................13
1. Introduction
A PPP/HDLC pseudowire (PW) allows PPP/HDLC Protocol Data Units (PDUs)
to be carried over an MPLS network. In addressing the issues
associated with carrying a PPP/HDLC PDU over an MPLS network, this
document assumes that a PW has been set up by some means outside the
scope of this document. This may be via manual configuration, or
using a signaling protocol such as that defined in [RFC4447].
The following figure describes the reference models that are derived
from [RFC3985] to support the HDLC/PPP PW emulated services. The
reader is also assumed to be familiar with the content of the
[RFC3985] document.
2. Specification of Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
Martini, et al. Standards Track [Page 2]
RFC 4618 Transport of PPP/HDLC over MPLS September 2006
|<-------------- Emulated Service ---------------->|
| |
| |<------- Pseudowire ------->| |
| | | |
| | |<-- PSN Tunnel -->| | |
| V V V V |
V AC +----+ +----+ AC V
+-----+ | | PE1|==================| PE2| | +-----+
| |----------|............PW1.............|----------| |
| CE1 | | | | | | | | CE2 |
| |----------|............PW2.............|----------| |
+-----+ ^ | | |==================| | | ^ +-----+
^ | +----+ +----+ | | ^
| | Provider Edge 1 Provider Edge 2 | |
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