One document matched: draft-jacquenet-qos-nlri-00.txt
Internet Engineering Task Force C. Jacquenet
INTERNET-DRAFT France Telecom R & D
Document: draft-jacquenet-qos-nlri-00.txt
Category: informational
Expires: January 2001
Providing Quality of Service Indication by the BGP-4 Protocol: the
QOS_NLRI attribute
<draft-jacquenet-qos-nlri-00.txt>
1. Status of this memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC 2026 ([RFC-2026]).
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
2. Abstract
For almost the last decade, value-added IP service offerings have
been massively deployed over the Internet, thus yielding a dramatic
development of the specification effort, as far as quality of
service (QOS) in IP networks is concerned. Nevertheless, providing
end-to-end quality of service by crossing administrative domains
still remains an issue, mainly because:
- quality of service policies may dramatically differ from one
service provider to another;
- the enforcement of a specific quality of service policy may also
differ from one domain to another, although the definition of a set
of basic and common quality of service indicators may be shared
between the service providers.
As far as IP routing is concerned, the BGP-4 protocol (Border
Gateway Protocol, version 4,[RFC-1771]) has been systematically
activated between autonomous systems for the purpose of exchanging
routing information related to the reachability of IP destination
prefixes. From this standpoint, the BGP-4 protocol appears to be one
of the key components for the enforcement of a global quality of
service policy, by allowing BGP peers to indicate each other if (1)
The QOS_NLRI attribute July 2000
they have the ability to announce QOS-related information when
transmitting UPDATE messages and (2) they have the ability to
process such a QOS-related information when conveyed in an UPDATE
message.
The purpose of this draft consists in proposing an additional BGP4
attribute, named the QOS_NLRI attribute, which aims at providing
QOS-related information related to the NLRI information conveyed in
a BGP UPDATE message.
3. 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 ([RFC-
2119]).
4. Introduction
Providing end-to-end quality of service is probably one of the most
important challenges of the Internet, not only because of the
massive development of value-added IP service offerings, but also
because of the various QOS policies that are currently deployed and
enforced within an autonomous system, and which may well differ from
one AS to another.
Activate the BGP-4 protocol for exchanging reachability information
between autonomous systems has been a must for many years, and, from
this standpoint, the BGP-4 protocol appears to be a key component in
the deployment of end-to-end QOS policies.
Exchanging QOS-related information as well as reachability
information in a given BGP UPDATE message might be helpful in
enforcing an end-to-end QOS policy.
This draft aims at specifying a new BGP-4 attribute, the QOS_NLRI
attribute which will convey QOS-related information associated to
the (possibly withdrawn) routes described in the NLRI (Network Layer
Reachability Information) field of a BGP UPDATE message.
5. The QOS_NLRI attribute (Type Code XY*)
*: "XY" is subject to the IANA considerations section of this draft.
This is an optional transitive attribute which can be used for the
following purposes:
(a) to advertise a QOS route to a peer. A QOS route is a route which
meets one or a set of QOS requirements to reach a given (set of)
destination prefixes. Such QOS requirements can be expressed in
terms of minimum transit delay to reach a destination, maximum
available bandwidth along the path to reach a destination, the
identification of the traffic which is expected to use this specific
route (identification means for such traffic include DSCP (DiffServ
Code Point, [RFC-2475]) marking), etc., and they can be provided as
The QOS_NLRI attribute July 2000
an input for the route calculation process embedded in the BGP peers
thanks to the activation of a signaling protocol, such as RSVP
(Resource ReSerVation Protocol, [RFC-2205]);
(b) to provide QOS information along with the NLRI information in a
single BGP UPDATE message. It is assumed that this QOS information
will be related to the route (or set of routes) described in the
NLRI field of the BGP UPDATE message.
The QOS_NLRI attribute is encoded as follows:
+---------------------------------------------------------+
| QOS Information Code (1 octet) |
+---------------------------------------------------------+
| QOS Information Sub-code (1 octet) |
+---------------------------------------------------------+
| QOS Information Value (2 octets) |
+---------------------------------------------------------+
| QOS Information Origin (1 octet) |
+---------------------------------------------------------+
| Network Address of Next Hop (1 octet) |
+---------------------------------------------------------+
| Network Layer Reachability Information (variable) |
+---------------------------------------------------------+
The use and meaning of these fields are as follows:
- QOS Information Code:
This field carries the type of the QOS information. The following
types have been identified so far:
(0) Reserved
(1) Bandwidth
(2) Delay
(3) Jitter
(4) DSCP
- QOS Information Sub-code:
This field carries the sub-type of the QOS information. The
following sub-types have been identified so far:
(0) None (i.e. no sub-type, or sub-type unavailable, or unknown sub-
type)
(1) Reserved bandwidth
(2) Available bandwidth
(3) Minimum transit delay
(4) Maximum transit delay
(5) Average transit delay
(6) AF (Assured Forwarding, [RFC-2597]) type
The instantiation of this sub-code field MUST be compatible with the
value conveyed in the QOS Information code field, as stated in the
The QOS_NLRI attribute July 2000
following table (the rows represent the QOS Information Code
possible values, the columns represent the QOS Information Sub-code
values identified so far, while the "X" sign indicates
incompatibility).
+----------------------------------------+
| | 0 | 1 | 2 | 3 | 4 | 5 | 6 |
+---------------------------------------+
| 0 | | | | | | | |
+---------------------------------------+
| 1 | | | | X | X | X | X |
+---------------------------------------+
| 2 | | X | X | | | | X |
+---------------------------------------+
| 3 | | X | X | X | X | X | X |
+---------------------------------------+
| 4 | | X | X | X | X | X | |
+---------------------------------------+
- QOS Information value:
This field indicates the value of the QOS information. The
corresponding units obviously depend on the instantiation of the QOS
Information Code. Namely, if:
(a) QOS Information Code field is "0", no unit specified,
(b) QOS Information Code field is "1", unit is bits per second
(bps),
(c) QOS Information Code field is "2", unit is milliseconds,
(d) QOS Information Code field is "3", unit is milliseconds,
(e) QOS Information Code field is "4", no unit specified.
- Network Address of Next Hop:
A variable length field that contains the Network Address of the
next router on the path to the destination prefix.
- Network Layer Reachability Information:
A variable length field that lists NLRI for the feasible routes that
are being advertised in this attribute.
The next hop information carried in the QOS_NLRI path attribute
defines the Network Layer address of the border router that should
be used as the next hop to the destinations listed in the QOS_NLRI
attribute in the UPDATE message. When advertising a QOS_NLRI
attribute to an external peer, a router may use one of its own
interface addresses in the next hop component of the attribute,
provided the external peer to which the route is being advertised
shares a common subnet with the next hop address. This is known as
a "first party" next hop.
A BGP speaker can advertise to an external peer an interface of any
internal peer router in the next hop component, provided the
external peer to which the route is being advertised shares a common
The QOS_NLRI attribute July 2000
subnet with the next hop address. This is known as a "third party"
next hop information.
A BGP speaker can advertise any external peer router in the next hop
component, provided that the Network Layer address of this border
router was learned from an external peer, and the external peer to
which the route is being advertised shares a common subnet with the
next hop address. This is a second form of "third party" next hop
information.
Normally the next hop information is chosen such that the shortest
available path will be taken. A BGP speaker must be able to support
disabling advertisement of third party next hop information to
handle imperfectly bridged media or for reasons of policy.
A BGP speaker must never advertise an address of a peer to that peer
as a next hop, for a route that the speaker is originating. A BGP
speaker must never install a route with itself as the next hop.
When a BGP speaker advertises the route to an internal peer, the
advertising speaker should not modify the next hop information
associated with the route. When a BGP speaker receives the route
via an internal link, it may forward packets to the next hop address
if the address contained in the attribute is on a common subnet with
the local and remote BGP speakers.
A BGP UPDATE message that carries the QOS_NLRI MUST also carry the
ORIGIN and the AS_PATH attributes (both in EBGP and in IBGP
exchanges). Moreover, in IBGP exchanges such a message MUST also
carry the LOCAL_PREF attribute. If such a message is received from
an external peer, the local system shall check whether the leftmost
AS in the AS_PATH attribute is equal to the autonomous system number
of the peer than sent the message. If that is not the case, the
local system shall send the NOTIFICATION message with Error Code
UPDATE Message Error, and the Error Subcode set to Malformed
AS_PATH.
An UPDATE message that carries no NLRI, other than the one encoded
in the QOS_NLRI attribute, should not carry the NEXT_HOP attribute.
If such a message contains the NEXT_HOP attribute, the BGP speaker
that receives the message should ignore this attribute.
6. Use of Capabilities Advertisement with BGP-4
A BGP speaker that uses the QOS_NLRI attribute SHOULD use the
Capabilities Advertisement procedures, as defined in [RFC-2842], so
that it might be able to determine if it can use such an attribute
with a particular peer.
The fields in the Capabilities Optional Parameter are defined as
follows:
- The Capability Code field is set to N (127 < N < 256, when
considering the "Private Use" range, as specified in [RFC-2434]),
while the Capability Length field is set to "1".
The QOS_NLRI attribute July 2000
- The Capability Value field is a one-octet field, encoded the same
way as the QOS Information Code field of the QOS_NLRI attribute.
7. IANA Considerations
Section 5 of this draft documents an optional transitive BGP-4
attribute named "QOS_NLRI" whose type value will be assigned by
IANA. To be completed.
8. Security considerations
This additional BGP-4 attribute specification does not change the
underlying security issues inherent in the existing BGP-4 protocol
specification [RFC-2385].
9. References
[RFC-1771] Y. Rekhter, T. Li, "A Border Gateway Protocol 4
(BGP-4)", RFC 1771, March 1995.
[RFC-2026] Bradner, S., "The Internet Standards Process --
Revision 3", BCP 9, RFC 2026, October 1996.
[RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997
[RFC-2205] R. braden et al., "Resource ReSerVation Protocol
(RSVP) - Version 1 Functional Specification", RFC
2205, September 1997.
[RFC-2385] A. Heffernan, "Protection of BGP sessions via the
TCP MD5 Signature Option", RFC 2385, August 1998.
[RFC-2434] T. Narten, H. Alvestrand, "Guidelines for Writing
an IANA Considerations Section in RFCs", RFC 2434,
October 1998.
[RFC-2475] S. Blake et al., "An Architecture for
Differentiated Services", RFC 2475, December 1998.
[RFC-2597] J. Heinanen et al., " Assured Forwarding PHB
Group", RFC 2597, June 1999.
[RFC-2842] R. Chandra, J. Scudder, "Capabilities Advertisement
with BGP-4", RFC 2842, May 2000.
10. Author's address
Christian Jacquenet
France Telecom R & D
42, rue des Coutures
BP 6243
14066 Caen cedex 04
France
Phone : + 33 2 31 75 94 28
Fax : + 33 2 31 73 56 26
Email : christian.jacquenet@francetelecom.fr
11. Full copyright statement
Copyright (C) The Internet Society (2000). All Rights Reserved.
The QOS_NLRI attribute July 2000
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provided that the above copyright notice and this paragraph are
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