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Network Working Group C. Jacquenet
Internet Draft France Telecom R&D
Document: draft-jacquenet-qos-nlri-01.txt November 2000
Category: Experimental
Expires: May 2001
Providing Quality of Service Indication by the BGP-4 Protocol: the
QOS_NLRI attribute
<draft-jacquenet-qos-nlri-01.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC 2026 [1].
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
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Abstract
This draft specifies an additional BGP4 (Border Gateway Protocol,
version 4, [2]) attribute, named the "QOS_NLRI" attribute, which aims
at providing QoS (Quality of Service)-related information associated
to the NLRI information conveyed in a BGP UPDATE message.
1. 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
(Autonomous System) to another.
For almost the last decade, value-added IP service offerings have
been deployed over the Internet, thus yielding a dramatic development
of the specification effort, as far as quality of service in IP
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networks is concerned. Nevertheless, providing end-to-end quality of
service by crossing administrative domains still remains an issue,
mainly because:
- QoS policies may dramatically differ from one service provider to
another,
- The enforcement of a specific QoS 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.
Activate the BGP4 protocol for exchanging reachability information
between autonomous systems has been a must for many years, and, from
this standpoint, the BGP4 protocol is one of the key components for
the enforcement of end-to-end QoS policies.
Therefore, exchanging QoS-related information as well as reachability
information in a given BGP UPDATE message appears to be helpful in
enforcing an end-to-end QoS policy.
This draft aims at specifying a new BGP4 attribute, the QOS_NLRI
attribute, that will convey QoS-related information associated to
the routes described in the corresponding NLRI (Network Layer
Reachability Information) field of a BGP UPDATE message.
This document is organized into the following sections:
- Section 3 identifies the changes that have been made in the
document since the last version,
- Section 4 describes the attribute and its mode of operation,
- Section 5 elaborates on the use of the capabilities advertisement
feature of the BGP4 protocol,
- Finally, sections 6 and 7 introduce IANA and some security
considerations, respectively.
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 [3].
3. Changes since the last version of this draft
The current version of this draft reflects the following changes:
- Re-wording of the Abstract section (summarized),
- Re-wording of the Introduction section (section 1),
- Insertion of the <AFI, SAFI> information in the QOS_NLRI attribute
(section 4),
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- Insertion of an acknowledgements section (section ,
- Revision of the
- Correction of remaining typos.
4. The QOS_NLRI attribute (Type Code XY*)
(*): "XY" is subject to the IANA considerations section of this
draft.
This is an optional transitive attribute that can be used for the
following purposes:
(a) To advertise a QoS route to a peer. A QoS route is a route that
meets one or a set of QoS requirement(s) to reach a given (set
of) destination prefixes (see [4], for example). 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, and/or the identification of the
traffic that is expected to use this specific route
(identification means for such traffic include DSCP (DiffServ
Code Point, [5]) marking). These QoS requirements can be used as
an input for the route calculation process embedded in the BGP
peers, e.g. thanks to the activation of a signaling protocol,
such as RSVP (Resource ReSerVation Protocol, [6]),
(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.
This draft makes no specific assumption about the means to actually
value this attribute, since this is mostly a matter of
implementation, but the reader is kindly suggested to have a look on
the [7], as an example of a means to feed the BGP peer with the
appropriate information.
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) |
+---------------------------------------------------------+
| Address Family Identifier (2 octets) |
+---------------------------------------------------------+
| Subsequent Address Family Identifier (1 octet) |
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+---------------------------------------------------------+
| Network Address of Next Hop (1 octet) |
+---------------------------------------------------------+
| Network Layer Reachability Information (variable) |
+---------------------------------------------------------+
The use and meaning of the fields of the QOS_NLRI attribute are
defined 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, [8]) 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
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 | |
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+---------------------------------------+
- 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.
- Address Family Identifier (AFI):
This field carries the identity of the Network Layer protocol
associated with the Network Address that follows. Presently defined
values for this field are specified in [9] (see the Address Family
Numbers section of this reference document).
- Subsequent Address Family Identifier (SAFI):
This field provides additional information about the type of the
Network Layer Reachability Information carried in the QOS_NLRI
attribute.
- 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, given 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.
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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 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.
5. 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 [10], so that it
might be able to determine if it can use such an attribute with a
particular peer.
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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 [11]), while
the Capability Length field is set to "1".
- The Capability Value field is a one-octet field, encoded the same
way as the QOS Information Code field of the QOS_NLRI attribute.
6. 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.
7. Security Considerations
This additional BGP-4 attribute specification does not change the
underlying security issues inherent in the existing BGP-4 protocol
specification [12].
8. References
[1] Bradner, S.,"The Internet Standards Process -- Revision 3", BCP
9, RFC 2026, October 1996.
[2] Rekhter Y., Li T., "A Border Gateway Protocol 4 (BGP-4)", RFC
1771, March 1995.
[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[4] Goderis D., T'Joens Y., Jacquenet C., Memenios G., Pavlou G.,
Egan R., Griffin D., Georgatsos P., Georgiadis L.,
"Specification of a Service Level Specification (SLS) Template",
draft-tequila-sls-00.txt, Work in Progress, November 2000. Check
http://www.ist-tequila.org for additional information.
[5] Nichols K., Blake S., Baker F., Black D., "Definition of the
Differentiated Services Field (DS Field) in the IPv4 and IPv6
Headers", RFC 2474, December 1998.
[6] Braden R. et al., "Resource ReSerVation Protocol (RSVP)- Version
1 Functional Specification", RFC 2205, September 1997.
[7] Jacquenet C., "A COPS client-type for IP traffic engineering",
draft-jacquenet-ip-te-cops-00.txt, Work in Progress, November
2000.
[8] Heinanen J. et al., " Assured Forwarding PHB Group", RFC 2597,
June 1999.
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[9] Reynolds J., Postel J., "ASSIGNED NUMBERS", RFC 1700, October
1994.
[10] R. Chandra, J. Scudder, "Capabilities Advertisement with
BGP-4", RFC 2842, May 2000.
[11] Narten T., Alvestrand H., "Guidelines for Writing an IANA
Considerations Section in RFCs", RFC 2434, October 1998.
[12] Heffernan A., "Protection of BGP sessions via the TCP MD5
Signature Option", RFC 2385, August 1998.
9. Acknowledgments
Part of this work is funded by the European Commission, within the
context of the TEQUILA (Traffic Engineering for Quality of Service in
the Internet At Large Scale, [4]) project, which is itself part of
the IST (Information Society Technologies) research program.
The author would also like to thank all the partners of the TEQUILA
project for the fruitful discussions that have been conducted within
the context of the traffic engineering specification effort of the
project.
10. Author's Addresses
Christian Jacquenet
France Telecom R & D
DMI/SIR
42, rue des Coutures
BP 6243
14066 CAEN Cedex 04
France
Phone: +33 2 31 75 94 28
Email: christian.jacquenet@francetelecom.fr
11. Full Copyright Statement
Copyright(C) The Internet Society (2000). All Rights Reserved.
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or assist its implementation may be prepared, copied, published and
distributed, in whole or in part, without restriction of any kind,
provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
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developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
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