draft-ietf-bier-path-mtu-discovery-01.txt   draft-ietf-bier-path-mtu-discovery-02.txt 
BIER Working Group G. Mirsky BIER Working Group G. Mirsky
Internet-Draft ZTE Corp. Internet-Draft ZTE Corp.
Intended status: Standards Track T. Przygienda Intended status: Standards Track T. Przygienda
Expires: July 21, 2017 Juniper Networks Expires: January 17, 2018 Juniper Networks
A. Dolganow A. Dolganow
Nokia Nokia
January 17, 2017 July 16, 2017
Path Maximum Transmission Unit Discovery (PMTUD) for Bit Index Explicit Path Maximum Transmission Unit Discovery (PMTUD) for Bit Index Explicit
Replication (BIER) Layer Replication (BIER) Layer
draft-ietf-bier-path-mtu-discovery-01 draft-ietf-bier-path-mtu-discovery-02
Abstract Abstract
This document describes Path Maximum Transmission Unit Discovery This document describes Path Maximum Transmission Unit Discovery
(PMTUD) in Bit Indexed Explicit Replication (BIER) layer. (PMTUD) in Bit Indexed Explicit Replication (BIER) layer.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 21, 2017. This Internet-Draft will expire on January 17, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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MTU: Maximum Transmission Unit MTU: Maximum Transmission Unit
OAM: Operations, Administration and Maintenance OAM: Operations, Administration and Maintenance
PMTUD: Path MTU Discovery PMTUD: Path MTU Discovery
1.1.2. Requirements Language 1.1.2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in BCP
[RFC2119]. 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Problem Statement 2. Problem Statement
[I-D.ietf-bier-oam-requirements] sets forth the requirement to define [I-D.ietf-bier-oam-requirements] sets forth the requirement to define
PMTUD protocol for BIER domain. This document describes the PMTUD protocol for BIER domain. This document describes the
extension to [I-D.ietf-bier-ping] for use in BIER PMTUD solution. extension to [I-D.ietf-bier-ping] for use in BIER PMTUD solution.
Current PMTUD mechanisms ([RFC1191], [RFC1981], and [RFC4821]) are Current PMTUD mechanisms ([RFC1191], [RFC8201], and [RFC4821]) are
primarily targeted to work on point-to-point, i.e. unicast paths. primarily targeted to work on point-to-point, i.e. unicast paths.
These mechanisms use packet fragmentation control by disabling These mechanisms use packet fragmentation control by disabling
fragmentation of the probe packet. As a result, a transient node fragmentation of the probe packet. As a result, a transient node
that cannot forward a probe packet that is bigger than its link MTU that cannot forward a probe packet that is bigger than its link MTU
sends to the packet source an error notification, otherwise the sends to the packet source an error notification, otherwise the
packet destination may respond with a positive acknowledgement. packet destination may respond with a positive acknowledgement.
Thus, possibly through a series of iterations, varying the size of Thus, possibly through a series of iterations, varying the size of
the probe packet, the packet source discovers the PMTU of the the probe packet, the packet source discovers the PMTU of the
particular path. particular path.
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its BMS and set size of the next probe as min(MTU, MTU') its BMS and set size of the next probe as min(MTU, MTU')
If upon expiration of the Echo Request timer BFIR didn't receive any If upon expiration of the Echo Request timer BFIR didn't receive any
Echo Replies, then the size of the probe SHOULD be decreased. There Echo Replies, then the size of the probe SHOULD be decreased. There
are scenarios when an implementation of the PMTUD would not decrease are scenarios when an implementation of the PMTUD would not decrease
the size of the probe. For example, if upon expiration of the Echo the size of the probe. For example, if upon expiration of the Echo
Request timer BFIR didn't receive any Echo Reply, then BFIR MAY Request timer BFIR didn't receive any Echo Reply, then BFIR MAY
continue to retransmit the probe using the initial size and MAY apply continue to retransmit the probe using the initial size and MAY apply
probe delay retransmission procedures. The algorithm used to delay probe delay retransmission procedures. The algorithm used to delay
retransmission procedures on BFIR is outside the scope of this retransmission procedures on BFIR is outside the scope of this
specification. The BFIR sends probes using BMS and locally defiined specification. The BFIR sends probes using BMS and locally defined
retransmission procedures until either the bit string is clear, i.e. retransmission procedures until either the bit string is clear, i.e.
contains no set bits, or until the BFIR retransmission procedure contains no set bits, or until the BFIR retransmission procedure
terminates and PMTU discovery is declared unsuccessful. In case of terminates and PMTU discovery is declared unsuccessful. In case of
convergence of the procedure, the size of the last probe indicates convergence of the procedure, the size of the last probe indicates
the PMTU size that can be used for all BFERs in the initial BMS the PMTU size that can be used for all BFERs in the initial BMS
without incurring fragmentation. without incurring fragmentation.
Thus we conclude that in order to comply with the requirement in Thus we conclude that in order to comply with the requirement in
[I-D.ietf-bier-oam-requirements]: [I-D.ietf-bier-oam-requirements]:
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6. Acknowledgement 6. Acknowledgement
Authors greatly appreciate thorough review and the most detailed Authors greatly appreciate thorough review and the most detailed
comments by Eric Gray. comments by Eric Gray.
7. References 7. References
7.1. Normative References 7.1. Normative References
[I-D.ietf-bier-architecture]
Wijnands, I., Rosen, E., Dolganow, A., Przygienda, T., and
S. Aldrin, "Multicast using Bit Index Explicit
Replication", draft-ietf-bier-architecture-05 (work in
progress), October 2016.
[I-D.ietf-bier-ping] [I-D.ietf-bier-ping]
Kumar, N., Pignataro, C., Akiya, N., Zheng, L., Chen, M., Kumar, N., Pignataro, C., Akiya, N., Zheng, L., Chen, M.,
and G. Mirsky, "BIER Ping and Trace", draft-ietf-bier- and G. Mirsky, "BIER Ping and Trace", draft-ietf-bier-
ping-00 (work in progress), July 2016. ping-01 (work in progress), January 2017.
[RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, [RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
DOI 10.17487/RFC1191, November 1990, DOI 10.17487/RFC1191, November 1990,
<http://www.rfc-editor.org/info/rfc1191>. <http://www.rfc-editor.org/info/rfc1191>.
[RFC1981] McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery
for IP version 6", RFC 1981, DOI 10.17487/RFC1981, August
1996, <http://www.rfc-editor.org/info/rfc1981>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU [RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU
Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007, Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007,
<http://www.rfc-editor.org/info/rfc4821>. <http://www.rfc-editor.org/info/rfc4821>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <http://www.rfc-editor.org/info/rfc8174>.
[RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed.,
"Path MTU Discovery for IP version 6", STD 87, RFC 8201,
DOI 10.17487/RFC8201, July 2017,
<http://www.rfc-editor.org/info/rfc8201>.
7.2. Informative References 7.2. Informative References
[I-D.ietf-bier-architecture]
Wijnands, I., Rosen, E., Dolganow, A., Przygienda, T., and
S. Aldrin, "Multicast using Bit Index Explicit
Replication", draft-ietf-bier-architecture-07 (work in
progress), June 2017.
[I-D.ietf-bier-oam-requirements] [I-D.ietf-bier-oam-requirements]
Mirsky, G., Nordmark, E., Pignataro, C., Kumar, N., Mirsky, G., Nordmark, E., Pignataro, C., Kumar, N.,
Aldrin, S., Zheng, L., Chen, M., Akiya, N., and S. Aldrin, S., Zheng, L., Chen, M., Akiya, N., and S.
Pallagatti, "Operations, Administration and Maintenance Pallagatti, "Operations, Administration and Maintenance
(OAM) Requirements for Bit Index Explicit Replication (OAM) Requirements for Bit Index Explicit Replication
(BIER) Layer", draft-ietf-bier-oam-requirements-03 (work (BIER) Layer", draft-ietf-bier-oam-requirements-03 (work
in progress), January 2017. in progress), January 2017.
Authors' Addresses Authors' Addresses
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