BFD Encapsulated in Large Packets
draft-ietf-bfd-large-packets-00
Network Working Group J. Haas
Internet-Draft Juniper Networks, Inc.
Intended status: Standards Track A. Fu
Expires: August 30, 2019 Bloomberg L.P.
February 26, 2019
BFD Encapsulated in Large Packets
draft-ietf-bfd-large-packets-00
Abstract
The Bidirectional Forwarding Detection (BFD) protocol is commonly
used to verify connectivity between two systems. BFD packets are
typically very small. It is desirable in some circumstances to know
that not only is the path between two systems reachable, but also
that it is capable of carrying a payload of a particular size. This
document discusses thoughts on how to implement such a mechanism
using BFD in Asynchronous mode.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to
be interpreted as described in [RFC2119] only when they appear in all
upper case. They may also appear in lower or mixed case as English
words, without normative meaning.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 30, 2019.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. BFD Encapsulated in Large Packets . . . . . . . . . . . . . . 3
3. Implementation and Deployment Considerations . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
6.1. Normative References . . . . . . . . . . . . . . . . . . 4
6.2. Informative References . . . . . . . . . . . . . . . . . 5
Appendix A. Related Features . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
The Bidirectional Forwarding Detection (BFD) [RFC5880] protocol is
commonly used to verify connectivity between two systems. However,
some applications may require that the Path MTU [RFC1191] between
those two systems meets a certain minimum criteria. When the Path
MTU decreases below the minimum threshold, those applications may
wish to consider the path unusable.
BFD may be encapsulated in a number of transport protocols. An
example of this is single-hop BFD [RFC5881]. In that case, the link
MTU configuration is typically enough to guarantee communication
between the two systems for that size MTU. BFD Echo mode
(Section 6.4 of [RFC5880]) is sufficient to permit verification of
the Path MTU of such directly connected systems. Previous proposals
([I-D.haas-xiao-bfd-echo-path-mtu]) have been made for testing Path
MTU for such directly connected systems. However, in the case of
multi-hop BFD [RFC5883], this guarantee does not hold.
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The encapsulation of BFD in multi-hop sessions is a simple UDP
packet. The BFD elements of procedure (Section 6.8.6 of [RFC5880])
covers validating the BFD payload. However, the specification is
silent on the length of the encapsulation that is carrying the BFD
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