draft-ietf-mpls-label-encaps-04.txt   draft-ietf-mpls-label-encaps-05.txt 
Network Working Group Eric C. Rosen Network Working Group Eric C. Rosen
Internet Draft Yakov Rekhter Internet Draft Yakov Rekhter
Expiration Date: October 1999 Daniel Tappan Expiration Date: February 2000 Daniel Tappan
Dino Farinacci Dino Farinacci
Guy Fedorkow Guy Fedorkow
Cisco Systems, Inc. Cisco Systems, Inc.
Tony Li Tony Li
Juniper Networks, Inc. Juniper Networks, Inc.
Alex Conta Alex Conta
Lucent Technologies Lucent Technologies
April 1999 August 1999
MPLS Label Stack Encoding MPLS Label Stack Encoding
draft-ietf-mpls-label-encaps-04.txt draft-ietf-mpls-label-encaps-05.txt
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
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material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Abstract Abstract
'Multi-Protocol Label Switching (MPLS)' [1,2] requires a set of "Multi-Protocol Label Switching (MPLS)" [1,2] requires a set of
procedures for augmenting network layer packets with 'label stacks', procedures for augmenting network layer packets with "label stacks",
thereby turning them into 'labeled packets'. Routers which support thereby turning them into "labeled packets". Routers which support
MPLS are known as 'Label Switching Routers', or 'LSRs'. In order to MPLS are known as "Label Switching Routers", or "LSRs". In order to
transmit a labeled packet on a particular data link, an LSR must transmit a labeled packet on a particular data link, an LSR must
support an encoding technique which, given a label stack and a support an encoding technique which, given a label stack and a
network layer packet, produces a labeled packet. This document network layer packet, produces a labeled packet. This document
specifies the encoding to be used by an LSR in order to transmit specifies the encoding to be used by an LSR in order to transmit
labeled packets on PPP data links, on LAN data links, and possibly on labeled packets on PPP data links, on LAN data links, and possibly on
other data links as well. On some data links, the label at the top other data links as well. On some data links, the label at the top
of the stack may be encoded in a different manner, but the techniques of the stack may be encoded in a different manner, but the techniques
described here MUST be used to encode the remainder of the label described here MUST be used to encode the remainder of the label
stack. This document also specifies rules and procedures for stack. This document also specifies rules and procedures for
processing the various fields of the label stack encoding. processing the various fields of the label stack encoding.
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3.5 Processing Labeled IPv6 Datagrams which are Too Big .... 15 3.5 Processing Labeled IPv6 Datagrams which are Too Big .... 15
3.6 Implications with respect to Path MTU Discovery ........ 16 3.6 Implications with respect to Path MTU Discovery ........ 16
4 Transporting Labeled Packets over PPP .................. 17 4 Transporting Labeled Packets over PPP .................. 17
4.1 Introduction ........................................... 17 4.1 Introduction ........................................... 17
4.2 A PPP Network Control Protocol for MPLS ................ 18 4.2 A PPP Network Control Protocol for MPLS ................ 18
4.3 Sending Labeled Packets ................................ 19 4.3 Sending Labeled Packets ................................ 19
4.4 Label Switching Control Protocol Configuration Options . 19 4.4 Label Switching Control Protocol Configuration Options . 19
5 Transporting Labeled Packets over LAN Media ............ 19 5 Transporting Labeled Packets over LAN Media ............ 19
6 IANA Considerations .................................... 20 6 IANA Considerations .................................... 20
7 Security Considerations ................................ 20 7 Security Considerations ................................ 20
8 Authors' Addresses ..................................... 20 8 Intellectual Property .................................. 20
9 References ............................................. 21 9 Authors' Addresses ..................................... 21
10 References ............................................. 22
1. Introduction 1. Introduction
"Multi-Protocol Label Switching (MPLS)" [1,2] requires a set of "Multi-Protocol Label Switching (MPLS)" [1,2] requires a set of
procedures for augmenting network layer packets with "label stacks", procedures for augmenting network layer packets with "label stacks",
thereby turning them into "labeled packets". Routers which support thereby turning them into "labeled packets". Routers which support
MPLS are known as "Label Switching Routers", or "LSRs". In order to MPLS are known as "Label Switching Routers", or "LSRs". In order to
transmit a labeled packet on a particular data link, an LSR must transmit a labeled packet on a particular data link, an LSR must
support an encoding technique which, given a label stack and a support an encoding technique which, given a label stack and a
network layer packet, produces a labeled packet. network layer packet, produces a labeled packet.
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variable size. variable size.
- An MPLS label has its meaning by virtue of an agreement between - An MPLS label has its meaning by virtue of an agreement between
the LSR that puts the label in the label stack (the "label the LSR that puts the label in the label stack (the "label
writer") , and the LSR that interprets that label (the "label writer") , and the LSR that interprets that label (the "label
reader"). However, the label stack does not provide any means of reader"). However, the label stack does not provide any means of
determining who the label writer was for any particular label. determining who the label writer was for any particular label.
If labeled packets are accepted from untrusted sources, the If labeled packets are accepted from untrusted sources, the
result may be that packets are routed in an illegitimate manner. result may be that packets are routed in an illegitimate manner.
8. Authors' Addresses 8. Intellectual Property
The IETF has been notified of intellectual property rights claimed in
regard to some or all of the specification contained in this
document. For more information consult the online list of claimed
rights.
9. Authors' Addresses
Eric C. Rosen Eric C. Rosen
Cisco Systems, Inc. Cisco Systems, Inc.
250 Apollo Drive 250 Apollo Drive
Chelmsford, MA, 01824 Chelmsford, MA, 01824
E-mail: erosen@cisco.com E-mail: erosen@cisco.com
Dan Tappan Dan Tappan
Cisco Systems, Inc. Cisco Systems, Inc.
250 Apollo Drive 250 Apollo Drive
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385 Ravendale Dr. 385 Ravendale Dr.
Mountain View, CA, 94043 Mountain View, CA, 94043
E-mail: tli@juniper.net E-mail: tli@juniper.net
Alex Conta Alex Conta
Lucent Technologies Lucent Technologies
300 Baker Avenue 300 Baker Avenue
Concord, MA, 01742 Concord, MA, 01742
E-mail: aconta@lucent.com E-mail: aconta@lucent.com
9. References 10. References
[1] Rosen, E., Viswanathan, A., and Callon, R., "Multiprotocol Label [1] Rosen, E., Viswanathan, A., and Callon, R., "Multiprotocol Label
Switching Architecture", Work in Progress, April 1999. Switching Architecture", Work in Progress, April 1999.
[2] Callon, R., Doolan, P., Feldman, N., Fredette, A., Swallow, G., [2] Callon, R., Doolan, P., Feldman, N., Fredette, A., Swallow, G.,
Viswanathan, A., "A Framework for Multiprotocol Label Switching", Viswanathan, A., "A Framework for Multiprotocol Label Switching",
Work in Progress, November 1997. Work in Progress, November 1997.
[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement [3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, BCP 14, March 1997. Levels", RFC 2119, BCP 14, March 1997.
 End of changes. 

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