One document matched: draft-venkatachalam-ospf-traffic-00.txt
Network Working Group Senthil Venkatachalam
Internet Draft Alcatel.
Expiration Date: November 2000 Ben Abarbanel
Alcatel.
OSPF Extensions to Support Inter-Area Traffic Engineering
draft-venkatachalam-ospf-traffic-00.txt
Status
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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.
Abstract
This document describes the OSPF "Traffic Engineering Summary LSA"
and its support to enable traffic engineering across area boundaries.
1. Introduction
Currently, there is no way to support traffic engineering across
areas using the OSPF protocol [1]. Previous work on traffic
engineering support [2] using the OSPF protocol has restricted the
focus to within an OSPF area. This draft proposes a new opaque
LSA [3] called the "Traffic Engineering Summary LSA" that helps
propagate the traffic engineering metric information across areas.
Senthil Venkatachalam, B. Abarbanel Expires November 2000 [Page 1]
Internet Draft draft-venkatachalam-ospf-traffic-00.txt May 2000
2. Traffic Engineering Summary LSA
The traffic engineering (TE) summary LSA will be originated by the
Area Border Router (ABR) into an area. This summary LSA is a type-10
opaque LSA, that will be flooded within the area. The functionality
of the TE summary LSA is similar to that of the summary LSA of
standard OSPF, but in addition it carries the traffic engineering
metrics to the remote destination (IP network or ASBR).
3. Traffic Engineering Attributes
The various traffic engineering attributes that are used to describe
the destination (either a network or an ASBR) in the TE summary LSA
are:
1 - Traffic engineering metric
2 - Hops
3 - Maximum bandwidth
4 - Unreserved bandwidth
5 - Delay
6 - Color
One or more of these attributes need to be used in the metrics
portion of the TE summary LSA.
The traffic engineering and hop metrics are additive metrics similar
to the ospf metric, but need not be the same. The traffic engineering
and hop metrics advertised by the router for the given summary
destination will have been computed in a manner similar to the
dijkstra computation for the ospf metric.
The maximum bandwidth to the summary destination is the largest of
all path-capacities, each associated with a possible path to the
destination. The path-capacity is the smallest link capacity of all
the links in the path. Hence, the maximum bandwidth is the maximum
amount of traffic that can be sent to that destination, when there
is no other traffic on the links.
The unreserved bandwidth to the summary destination is the largest
of all path-unreserved bandwidths, each associated with a possible
path to the destination. The path-unreserved bandwidth is the
smallest unreserved bandwidth of all the links in the path. Hence,
the unreserved bandwidth is the maximum amount of traffic that can
currently be sent to that destination, the other traffic on the
links being steady.
Senthil Venkatachalam, B. Abarbanel Expires November 2000 [Page 2]
Internet Draft draft-venkatachalam-ospf-traffic-00.txt May 2000
The delay is an additive metric. The value of the delay attribute
for a summary destination will have been determined through a
dijkstra computation based on the delay.
The value of the color attribute to the summary destination is some
combination of the path-colors, each associated with a possible path
to the destination. The path-color is a combination of the colors of
the links in the path. Usually, this combination is a "logical and"
of the colors.
Once these attributes are determined for the destination networks
and ASBRs, the advertising ABR then creates the TE summary LSA to be
flooded out of its interfaces into the area. The ABR should generate
a new TE summary LSA when the attributes change, or other normal
OSPF behavior require it.
4. The TE Summary LSA Format
The TE summary LSA has the basic LSA structure with a modified
opaque LSA header called the TE summary LSA header. The TE summary
LSA contents include a destination field, network mask, and
TLV-tuples describing the traffic engineering attributes.
4.1 TE Summary LSA Header
The TE summary LSA's header is derived from the standard and opaque
LSA headers. The LS type field is assigned the value 10 to denote
that this is an opaque LSA of type-10 or area-local scope.
The Link State ID field of the standard LSA header is replaced by
the Opaque Type (1 octet), TE-LS Type (1 octet) and the TE-summary
LSA ID (2 octets). The value of the opaque type field for the
TE-summary LSA is TBD. The TE-LS Type can take values 3 or 4,
depending on whether the destination being described in the LSA is
an IP network or an ASBR respectively. The TE-summary LSA ID is a
unique 16-bit number that helps identify the TE Summary LSA.
A total of 65536 TE summary LSAs can be originated by an ABR.
Senthil Venkatachalam, B. Abarbanel Expires November 2000 [Page 3]
Internet Draft draft-venkatachalam-ospf-traffic-00.txt May 2000
The format of the TE summary LSA header is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | 10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Opaq. Type(TBD)|TE LS Type=3/4 | TE Summary LSA ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.2 TE Summary LSA Contents
The summary LSA consists of:
o The Destination ID, which is:
o The IP address of the described network (if TE LS Type = 3),
or
o The Router ID of the described ASBR (if TE LS Type = 4).
(The functionality of the destination ID field is the same as the
LS ID field in the standard summary LSA header). This field is
4 octets in length.
o The Network Mask, which holds the mask of the network described in
the summary. If the summary is for an ASBR, this field is set to 0.
(The functionality is the same as in the standard summary LSA).
This field is 4 octets in length. It is followed by:
o One or more TLV-tuples that describe the traffic engineering
metrics to reach the network or the ASBR defined in the TE summary
LSA. These TLV-tuples have a constant "type" and "length"
field-lengths of 2 octets each, and a variable length "value"
field. The length field specifies the length of the value field in
bytes. The TLV is padded to the standard 4-byte alignment.
Senthil Venkatachalam, B. Abarbanel Expires November 2000 [Page 4]
Internet Draft draft-venkatachalam-ospf-traffic-00.txt May 2000
The contents of the TE summary LSA is then of the following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Network Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value (4x octets, x >= 0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.3 The Traffic Engineering Attributes
The following traffic engineering attributes are defined:
1 - Traffic engineering metric (4 octets)
2 - Hops (4 octets)
3 - Maximum bandwidth (4 octets)
4 - Unreserved bandwidth (4 octets)
5 - Delay (4 octets)
6 - Resource class/color (4 octets)
Some of these traffic engineering attributes have sizes the same as
in [2] but others (notably the bandwidths) are not. The bandwidths
have been kept to just 4 octets to restrict the size of the TLV.
Each of these attributes (and the value associated with it) is
represented as a TLV-tuple. Each such attribute may occur at most
once (none or once) in an LSA. In addition, new traffic engineering
attributes may be defined in the future.
The TLV attributes are as follows (see Section 3 for the definition):
4.3.1 Traffic Engineering Metric
The traffic engineering metric represents the traffic engineering
cost of reaching the destination network or ASBR from the
advertising ABR. The TLV-type is 1, and the length of this
attribute is 4 octets.
Senthil Venkatachalam, B. Abarbanel Expires November 2000 [Page 5]
Internet Draft draft-venkatachalam-ospf-traffic-00.txt May 2000
4.3.2 Hops
The hops TLV is the cost in hops, of reaching the destination
network or ASBR from the advertising ABR. The TLV-type is 2, and the
length is 4 octets.
4.3.3 Maximum Bandwidth
The maximum bandwidth to the destination is described in bytes/second
as an IEEE floating point number. The TLV-type is 3, and the length
is 4 octets.
4.3.4 Unreserved Bandwidth
The unreserved bandwidth to the destination is described in
bytes/second as an IEEE floating point number. The TLV-type is 4,
and the length is 4 octets.
4.3.5 Delay
The delay attribute is the delay cost to reach the destination
network (or ASBR), in milliseconds, represented as an unsigned
(4-byte) long integer. The TLV-type is 5, and the length is 4 octets.
4.3.6 Resource Class/Color
The resource class or color of the destination network (or ASBR) is a
combination of the colors for the various paths to the network
(or ASBR). The TLV-type of the resource class/color attribute is 6,
and the length is 4 octets.
5. Use of the Traffic Engineering Summary LSA
The TE summary LSA provides the traffic engineering information
regarding remote destinations (networks or ASBRs) in other areas.
This information is valuable in order to make accurate routing
decisions based on attributes such as bandwidth, delay, metrics and
colors. The TE summary LSAs along with the TE LSAs [2] provide a
comprehensive traffic topology of the OSPF domain. Using this
traffic topology database, routing calculations can be performed
based on a variety of criteria which could be combinations of
constraints [4] on one or more traffic engineering attributes.
Senthil Venkatachalam, B. Abarbanel Expires November 2000 [Page 6]
Internet Draft draft-venkatachalam-ospf-traffic-00.txt May 2000
Such a traffic topology database can be used:
1. to effect QoS routing, by precomputing routes to remote
destinations based on a fixed combination of traffic engineering
constraints,
2. to calculate a route to a remote destination based on traffic
engineering constraints, on an as-needed basis,
3. to determine the traffic engineering "distance" from an ASBR to
the various networks and other ASBRs in the domain, so that this
information can be redistributed into BGP, and be propagated
outside of the domain[5]. This setup can help in the distribution
of traffic engineering information across ASs.
6. Compatibility Issues
Three different cases are possible with respect to an ABR's support
of the TE summary LSA:
1. The ABR doesn't support opaque LSAs, in which case the opaque LSAs
received by it are simply ignored, and none are generated or
forwarded.
2. The ABR supports opaque LSAs, but not the TE summary LSA, in which
case it floods out any TE summary LSA received from one of its
interfaces out of other interfaces in the same area. However, no
TE summary LSAs are generated into an area.
3. The ABR supports the TE summary LSA. In this case, the TE summary
LSA is generated for each area and flooded out the interfaces of
that area.
If a router interior to an area doesn't support TE summary LSAs, it
will not be able to take advantage of the traffic engineering
attributes of remote destinations outside the area, and hence will
not be able to calculate remote routes based on these attributes.
If a router interior to an area doesn't support TE LSAs from [2],
the TE summary LSAs generated by the ABR of the area will describe
a traffic topology that is smaller than the underlying network
topology. Hence if all the routes of the underlying network topology
need to be represented in the traffic topology, all routers in the
area must support the TE LSAs.
Senthil Venkatachalam, B. Abarbanel Expires November 2000 [Page 7]
Internet Draft draft-venkatachalam-ospf-traffic-00.txt May 2000
7. Security Considerations
There are no new security considerations necessary beyond that of[1].
8. References
[1] Moy, J., "OSPF Version 2", RFC 2328, April 1998.
[2] Katz, D. and Yeung D., "Traffic Engineering Extensions to OSPF",
Internet Draft <draft-katz-yeung-ospf-traffic-00.txt>
[3] Coltun, R., "The OSPF Opaque LSA Option," RFC 2370, July 1998.
[4] Awduche, D. et al "Extensions to RSVP for LSP Tunnels", Work in
Progress, Internet Draft <draft-ietf-mpls-rsvp-lsp-tunnel-04.txt,
September 1999.
[5] Abarbanel, B. and Venkatachalam, Senthil, "BGP-4 support for
Traffic Engineering", Internet Draft
<draft-abarbanel-idr-bgp4-te-00.txt>
9. Authors' Addresses
Senthil Venkatachalam
Alcatel USA
45195 Business Court, Suite 400
Dulles, VA 20166
email: senthil.venkatachalam@usa.alcatel.com
Phone: (703)654-8635
Ben Abarbanel
Alcatel USA
45195 Business Court, Suite 400
Dulles, VA 20166
email: benjamin.abarbanel@usa.alcatel.com
home email: ben@baces.com
Senthil Venkatachalam, B. Abarbanel Expires November 2000 [Page 7]
| PAFTECH AB 2003-2026 | 2026-04-24 05:02:20 |