Pseudowire Emulation Edge-to-Edge (PWE3) Fragmentation and Reassembly
RFC 4623
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RFC - Proposed Standard
(August 2006; Errata)
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Last updated |
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2020-01-21
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IETF
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plain text
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pdf
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with errata
bibtex
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WG state
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No shepherd assigned
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IESG state |
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RFC 4623 (Proposed Standard)
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Unknown
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Responsible AD |
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Margaret Cullen
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Send notices to |
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stbryant@cisco.com, danny@arbor.net
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Network Working Group A. Malis
Request for Comments: 4623 Tellabs
Category: Standards Track M. Townsley
Cisco Systems
August 2006
Pseudowire Emulation Edge-to-Edge (PWE3)
Fragmentation and Reassembly
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
This document defines a generalized method of performing
fragmentation for use by Pseudowire Emulation Edge-to-Edge (PWE3)
protocols and services.
Malis & Townsley Standards Track [Page 1]
RFC 4623 PWE3 Fragmentation and Reassembly August 2006
Table of Contents
1. Introduction ....................................................3
2. Conventions Used in This Document ...............................4
3. Alternatives to PWE3 Fragmentation/Reassembly ...................5
4. PWE3 Fragmentation with MPLS ....................................5
4.1. Fragment Bit Locations for MPLS ............................6
4.2. Other Considerations .......................................6
5. PWE3 Fragmentation with L2TP ....................................6
5.1. PW-Specific Fragmentation vs. IP fragmentation .............7
5.2. Advertising Reassembly Support in L2TP .....................7
5.3. L2TP Maximum Receive Unit (MRU) AVP ........................8
5.4. L2TP Maximum Reassembled Receive Unit (MRRU) AVP ...........8
5.5. Fragment Bit Locations for L2TPv3 Encapsulation ............9
5.6. Fragment Bit Locations for L2TPv2 Encapsulation ............9
6. Security Considerations ........................................10
7. IANA Considerations ............................................10
7.1. Control Message Attribute Value Pairs (AVPs) ..............11
7.2. Default L2-Specific Sublayer Bits .........................11
7.3. Leading Bits of the L2TPv2 Message Header .................11
8. Acknowledgements ...............................................11
9. Normative References ...........................................12
10. Informative References ........................................12
Appendix A. Relationship Between This Document and RFC 1990 .......14
Malis & Townsley Standards Track [Page 2]
RFC 4623 PWE3 Fragmentation and Reassembly August 2006
1. Introduction
The Pseudowire Emulation Edge-to-Edge Architecture Document
[Architecture] defines a network reference model for PWE3:
|<-------------- Emulated Service ---------------->|
| |
| |<------- Pseudowire ------->| |
| | | |
| | |<-- PSN Tunnel -->| | |
| PW End V V V V PW End |
V Service +----+ +----+ Service V
+-----+ | | PE1|==================| PE2| | +-----+
| |----------|............PW1.............|----------| |
| CE1 | | | | | | | | CE2 |
| |----------|............PW2.............|----------| |
+-----+ ^ | | |==================| | | ^ +-----+
^ | +----+ +----+ | | ^
| | Provider Edge 1 Provider Edge 2 | |
| | | |
Customer | | Customer
Edge 1 | | Edge 2
| |
| |
native service native service
Figure 1: PWE3 Network Reference Model
A Pseudowire (PW) payload is normally relayed across the PW as a
single IP or MPLS Packet Switched Network (PSN) Protocol Data Unit
(PDU). However, there are cases where the combined size of the
payload and its associated PWE3 and PSN headers may exceed the PSN
path Maximum Transmission Unit (MTU). When a packet exceeds the MTU
of a given network, fragmentation and reassembly will allow the
packet to traverse the network and reach its intended destination.
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