Internet DRAFT - draft-venaas-pim-pfm-sd-subtlv
draft-venaas-pim-pfm-sd-subtlv
Network Working Group S. Venaas
Internet-Draft Cisco Systems, Inc.
Intended status: Experimental F. Meo
Expires: 5 September 2024 4 March 2024
PIM Flooding Mechanism and Source Discovery Sub-TLV
draft-venaas-pim-pfm-sd-subtlv-01
Abstract
PIM Flooding Mechanism and Source Discovery (RFC 8364) allows for
announcement of active sources, but it does not allow for providing
additional information about the flow. This document defines a new
TLV for announcing sources that allows for Sub-TLVs that can be used
for providing various types of information. This document defines a
Sub-TLV for flow data rate.
Status of This Memo
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This Internet-Draft will expire on 5 September 2024.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . 2
3. Group Source Holdtime Info TLV . . . . . . . . . . . . . . . 2
4. Group Source Holdtime Info Flow data rate Sub-TLV . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Normative References . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
It may be useful to provide additional information about flows in PFM
[RFC8364] source announcements. One such case is flow data rate.
Routers may use this information in various ways, for instance to
decide whether there is sufficient available bandwidth to join the
tree or in case of ECMP, selecting an interface that has sufficient
available bandwidth.
This document defines a new TLV for announcing sources that allows
for Sub-TLVs that can be used providing various types of information.
It also defines a Sub-TLV for flow data rate.
2. Conventions Used in This Document
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 RFC 2119 [RFC2119].
3. Group Source Holdtime Info TLV
PFM-SD [RFC8364] defines a Group Source Holdtime (GSH) TLV for
announcing active sources. This document defins a new Group Source
Holdtime Info (GSHI) TLV that is used similarly to the GSH TLV except
that it only provides info for a single source, and includes
additional information about the flow in Sub-TLVs.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|T| Type = TBD | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group Address (Encoded-Group format) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Src Address 1 (Encoded-Unicast format) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Src Holdtime | Type Sub-TLV 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length Sub-TLV 1 | Value Sub-TLV 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| . |
| . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . |
| . |
| Type Sub-TLV n | Length Sub-TLV n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value Sub-TLV n
| . |
| . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
T: If the Transitive bit is set to 0, a router MUST NOT forward the
message unless it supports this TLV and all the Sub-TLVs that are
present in the TLV in this message. If the transitive bit is set
to 1, it is forwarded even if the router does not support the TLV
or all the Sub-TLVs present.
Type: This TLV has type TBD.
Length: The length of the value in octets.
Group Address: The group that sources are to be announced for. The
format for this address is given in the Encoded-Group format in
[RFC7761].
Src Address: The source address for the corresponding group. The
format for these addresses is given in the Encoded-Unicast address
in [RFC7761].
Src Holdtime: The Holdtime (in seconds) for the included source(s).
Type Sub-TLV 1..n: The TLV contains n Sub-TLVs, n MAY be 0. The
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total length of the TLV (the Length field) is used to derive the
how many octets are used for Sub-TLVs. It will be at least 4 * n
octets if n Sub-TLVs are present. Type Sub-TLV indicates the type
of the Sub-TLV. The allowed types are Sub-TLV types that are
specifically defined for use in the Group Source Holdtime Info
TLV. This document defines one such Sub-TLV type.
Length Sub-TLV 1..n: The length of the Sub-TLV Value field in
octets.
Value Sub-TLV 1..n: The value of the Sub-TLV associated with the
type and of the specified length.
4. Group Source Holdtime Info Flow data rate Sub-TLV
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = TBD | Length = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Exponent | Significand |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: This TLV has type TBD.
Length: The length of the value in octets. The length is always 2.
Exponent and Significand: The value of the TLV contains Exponent and
Significand, each is 1 octet. These are used to indicate the flow
data rate as specified below.
The data rate of a flow is specified using the Exponent and
Significand fields. The rate is Significand * 10 ^ Exponent kbps.
This allows specifying the rate with up to 3 decimal digits precision
and speeds from 1 kbps to 10 ^ 67 kbps. A computed speed of 0 kbps
means the rate is less than 1 kbps.
Here are some examples of how this is used:
Link Speed Exponent Significand
------------ ---------- -------------
500 kbps 0 500
500 kbps 2 5
155 Mbps 3 155
40 Gpbs 6 40
100 Gpbs 6 100
100 Gpbs 8 1
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5. Security Considerations
When it comes to general PIM message security, see [RFC7761]. For
PFM security see [RFC8364].
This document defines a new format allowing for additional flow
information. One concern is what happens if wrong information is
provided by accident, or intentionally in a sppofed message by an
attacker. The impact depends on what information is provided.
This document defines a Sub-TLV for flow data rate. If the rate
provided is not correct, a router may make decisions using the wrong
rate. If the rate indicated is too high, a router may for instance
decide not to join assuming there is not sufficient bandwidth
available. If it is too low, the router may join even if there is
not sufficient bandwidth, causing packet drops.
6. IANA Considerations
This document requires the assignment of a new PFM TLV type in the
"PIM Flooding Mechanism Message Types" registry. Also, a new
registry "PFM Group Source Holdtime Info Sub-Types" registry needs to
be created. Assignments for the new registry are to be made
according to the policy "IETF Review" as defined in [RFC8126]. The
initial content of the registry should be:
Sub-Type Name Reference
------------------------------------------------------
0 Reserved [this document]
1 Flow data rate [this document]
2-32767 Unassigned
7. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I.,
Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent
Multicast - Sparse Mode (PIM-SM): Protocol Specification
(Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March
2016, <https://www.rfc-editor.org/info/rfc7761>.
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[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8364] Wijnands, IJ., Venaas, S., Brig, M., and A. Jonasson, "PIM
Flooding Mechanism (PFM) and Source Discovery (SD)",
RFC 8364, DOI 10.17487/RFC8364, March 2018,
<https://www.rfc-editor.org/info/rfc8364>.
Authors' Addresses
Stig Venaas
Cisco Systems, Inc.
Tasman Drive
San Jose, CA 95134
United States of America
Email: stig@cisco.com
Francesco Meo
Email: fran.meo@gmail.com
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