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Francois Le Faucheur
Thomas D. Nadeau
Cisco Systems, Inc.
Angela Chiu
celion Networks
William Townsend
Tenor Networks
Darek Skalecki
Nortel Networks
IETF Internet Draft
Expires: August, 2001
Document: draft-ietf-isis-diff-te-00.txt February, 2001
Extensions to ISIS
for support of Diff-Serv-aware MPLS Traffic Engineering
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. Internet-Drafts are
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Abstract
A companion document [DIFF-TE-REQTS] defines the requirements for
support of Diff-Serv-aware MPLS Traffic Engineering on a per-Class-
Type basis, as discussed in the Traffic Engineering Working Group
Framework document [TEWG-FW].
This document proposes corresponding extensions to ISIS for support
of Traffic Engineering on a per-Class-Type basis.
Le Faucheur, et. al 1
ISIS Extensions for Diff-Serv Traffic Engineering Feb 2001
Two companion documents [DIFF-TE-EXT] [DIFF-TE-OSPF] propose
corresponding extensions to RSVP and CR-LDP and to OSPF for support
of Traffic Engineering on a per-Class-Type basis.
1. Introduction
As Diffserv becomes prominent in providing scalable multi-class of
services in IP networks, performing traffic engineering at a per-
class level instead of an aggregated level is needed in networks
where fine optimisation of resources is sought in order to further
enhance performance and efficiency. By mapping a traffic trunk in a
given class on a separate LSP, it allows the traffic trunk to
utilize resources available on both shortest path(s) and non-
shortest paths and follow paths that meet constraints which are
specific to the given class. It also allows each class to select the
proper protection/restoration mechanism(s) that satisfy its
survivability requirements in a cost effective manner.
Besides the set of parameters defined for the general aggregate TE
[TE-REQ], a new set of per-class parameters needs to be provided at
each LSR interface and propagated via extensions to the IGP
(ISIS/OSPF) [TEWG-FW]. Furthermore, the per-class parameters can be
aggregated into per-Class-Type parameters. The main motivation for
grouping a set of classes into a Class-Type is to improve the
scalability of the IGP link state advertisements by propagating
information on a per-Class-Type basis instead of on a per-class
basis. This approach also has the benefit of allowing better
bandwidth sharing between classes in the same Class-Type.
A Class-Type [TEWG-FW] is defined as a set of classes that satisfy
the following two conditions:
1) Classes in the same Class-Type possess common aggregate maximum
and minimum bandwidth requirements to guarantee the required
performance level.
2) There is no maximum or minimum bandwidth requirement to be
enforced at the level of an individual class within the Class-
Type. One can still implement some "priority" policies for
classes within the same Class-Type in terms of accessing the
Class-Type bandwidth (e.g. via the use of preemption
priorities).
An example of Class-Type comprising multiple Diff-Serv classes is a
low-loss Class-Type that includes both AF1-based and AF2-based
Ordering Aggregates.
Note that with per Class-Type TE, Constraint-Based Routing is
performed with bandwidth constraints on a per Class-Type basis but
LSPs may carry a single Diff-Serv class (Ordered Aggregate) with
Diff-Serv scheduling (i.e. PHB) performed separately for each class.
Le Faucheur et. al 2
ISIS Extensions for Diff-Serv Traffic Engineering Feb 2001
In this document, we will only discuss "per Class-Type TE" because
"per Class TE" can be viewed as a special case of per Class-Type TE
(where each Class-Type is degenerated into a single Diff-Serv
class).
This document focuses on intra-domain operations. Inter-domain
operations is for further study.
A companion document [DIFF-TE-REQTS] defines the requirements for
support of MPLS Traffic Engineering on a per-Class-Type basis. The
following sections propose detailed extensions to ISIS that meet
those requirements.
Two companion documents [DIFF-TE-EXT] [DIFF-TE-OSPF] propose
corresponding extensions to RSVP and CR-LDP and to OSPF for support
of Traffic Engineering on a per-Class-Type basis.
2. ISIS Extensions
In this section we describe extensions to IS-IS for support of Diff-
Serv Traffic Engineering on a per-Class-Type basis which meet the
requirements defined in [DIFF-TE-REQTS]. These extensions are in
addition to the extensions required to support (aggregate) MPLS
Traffic Engineering defined in [ISIS-TE].
2.1. Existing TE sub-TLVs
[ISIS-TE] defines new extended TLVs for support of (aggregate)
Traffic Engineering. One of these extended TLV is referred to as the
extended IS reachability TLV (TLV type 22). This TLV contains a
number of new sub-TLVs.
In this document we refer to the sub-TLV 10 (Maximum reservable link
bandwidth) of the extended IS reachability TLV (as defined in [ISIS-
TE]) as the "Maximum Reservable Aggregate Bandwidth".
We also refer to the sub-TLV 11 (unreserved bandwidth) of the
extended IS reachability TLV (as defined in [ISIS-TE]) as the
"Unreserved Bandwidth for Class-Type 0".
2.2. New Sub-TLVs
The following additional sub-TLVs are defined for the extended IS
reachability TLV (sub-TLV numbers to be allocated):
TBD1 - Unreserved bandwidth for Class-Type 1
TBD2 - Unreserved bandwidth for Class-Type 2
TBD3 - Unreserved bandwidth for Class-Type 3
Each sub-TLV may occur only once. Unrecognized types are ignored.
Le Faucheur et. al 3
ISIS Extensions for Diff-Serv Traffic Engineering Feb 2001
The additional sub-TLVs defined above are optional so that they may
or may not be included in the extended IS reachability TLV.
The extended IS reachability TLV may include the sub-TLVs for any
subset of the three additional Class-Types. In other words, the IS
reachability TLV may contain none of the three sub-TLVs defined
above, any one of those, any two of those, or the three sub-TLVs.
As discussed in [DIFF-TE-REQTS], where a Class-Type is not
effectively used in a network, it is recommended that the
corresponding sub-TLV is not included in the IS reachability TLV.
Therefore, the Class-Types to be advertised in ISIS should be
configurable. For instance, a Network Administrator may elect to use
Diff-Serv Traffic Engineering in order to compute separate routes
for data traffic and voice traffic (and apply different bandwidth
constraints to the route computation for those). In that case, the
IGP would be configured to only advertise the sub-TLV for one
additional Class-Type (i.e. the extended IS reachability TLV would
contain sub-TLV 10 for the Maximum Reservable Aggregate Bandwidth,
sub-TLV 11 for the Unreserved Bandwidth for Class-Type 0 and sub-TLV
TBD1 for Unreserved Bandwidth for Class-Type 1).
An LSR which supports Class-Type N and receiving an extended IS
reachability TLV without the sub-TLV corresponding to Class-Type N,
must interpret this as meaning that the corresponding link does not
support Class-Type N. For Constraint Based Routing purposes, the LSR
may consider this equivalent to the case where the extended IS
reachability TLV contains an Unreserved Bandwidth Class-Type N sub-
TLV with bandwidth values set to zero.
An LSR which does not support Class-Type N and which receives an
extended IS reachability TLV containing the sub-TLV corresponding to
Class-Type N, must ignore this sub-TLV. However, the IS reachability
TLV must be flooded transparently, so that the sub-TLV for Class-
Type N is kept in the IS reachability TLV when reflooded by this
LSR.
2.3. Sub-TLV Details
The Unreserved Bandwidth for Class-Type N (N= 1,2,3) sub-TLVs
specifies the amount of bandwidth not yet reserved for Class-Type N
at each of the eight preemption priority levels. Each value will be
less than, or equal to, the Maximum Reservable Bandwidth for Class-
Type N.
When the bandwidth value for preemption Z (Z > 0) is identical to
the bandwidth value for preemption Z-1, the bandwidth value for
preemption Z is not explicitly repeated in the sub-TLV. Rather, the
fact that it is identical to the value of preemption Z-1, is encoded
in a "repetition octet".
Le Faucheur et. al 4
ISIS Extensions for Diff-Serv Traffic Engineering Feb 2001
Thus, the sub-TLV comprises:
- P (1<=P<=8) bandwidth values. These values correspond to the
bandwidth that can be reserved with a holding priority of 0 through
7, arranged in increasing order with priority 0 occurring at the
start of the sub-TLV, and priority 7 towards the end of the sub-TLV,
but omitting all repeated values. The units are bytes per second and
the values are encoded in IEEE floating point format.
- a "repetition octet" where each bit is referred to as bitZ ,
0 <= Z < 8, and is defined to have the following meaning:
* if bitZ = 0 then "Unreserved Bandwidth" for preemption
level Z is explicitely included in the sub-TLV,
* if bitZ = 1 then "Unreserved Bandwidth" for preemption
level Z is not explicitely included in the sub-TLV but is
defined to be equal to "Unreserved Bandwidth" for preemption
level Z-1.
Note that the highest preemption level (level 0) is always
advertised and the first bit (Bit0) in the "repetition octet" is
always set to 0.
[Editor's note: should the "repetition octet" be moved before the
bandwidth values?]
The Unreserved Bandwidth for Class-Type N sub-TLV is TLV type
(TBDN). Its length is (P*4 +1), where 1<=P<=8 and where P is the
number of non-equal bandwidth values across all preemption levels
for that Class-Type.
For example, when a link supports LSPs of preemption levels 2 and 4
only (for a particular Class-Type) with "Unreserved Bandwidth" (for
the particular Class-Type) on that link for preemption levels 0, 2,
and 4 currently of 10Mb/s, 5Mb/s and 3Mb/s, respectively, then
"Unreserved Bandwidth" (for the particular Class-Type) for
preemption levels 0, 2, and 4 of 10Mb/s, 5Mb/s and 3Mb/s,
respectively, are explicitly advertised for that link as well as
"repetition octet" of 01010111 in binary form. The sub-TLV length is
13.
3. Security Considerations
This document raises no new security issues for IS-IS. The security
mechanisms already proposed for ISIS may be used.
4. Acknowledgments
This document has benefited from discussions with Carol Iturralde .
Le Faucheur et. al 5
ISIS Extensions for Diff-Serv Traffic Engineering Feb 2001
References
[TE-REQ] Awduche et al, Requirements for Traffic Engineering over
MPLS, RFC2702, September 1999.
[TEWG-FW] Awduche et al, A Framework for Internet Traffic
Engineering, draft-ietf-tewg-framework-02.txt, July 2000.
[DIFF-TE-REQTS] Le Faucheur et al, Requirements for support of
Diff-Serv-aware MPLS Traffic Engineering, draft-ietf-tewg-diff-te-
reqts-00.txt, February 2001.
[DIFF-TE-OSPF] Le Faucheur et al, Extension to OSPF for support of
Diff-Serv-aware MPLS Traffic Engineering, draft-ietf-ospf-diff-te-
00.txt, February 2001.
[DIFF-TE-EXT] Le Faucheur et al, Extension to RSVP and CR-LDP for
support of Diff-Serv-aware MPLS Traffic Engineering, draft-ietf-
mpls-diff-te-ext-01.txt, February 2001.
[ISIS-TE] Smit, Li, IS-IS extensions for Traffic Engineering, draft-
ietf-isis-traffic-02.txt, September 2000.
Authors' Address:
Francois Le Faucheur
Cisco Systems, Inc.
Petra B - Les Lucioles - 291, rue Albert Caquot - 06560 Valbonne -
France
Phone: +33 4 92 96 75 64
Email: flefauch@cisco.com
Angela Chiu
Celion Networks
1 Sheila Drive, Suite 2
Tinton Falls, NJ 07724
Phone: +1-732 747 9987
Email: angela.chiu@celion.com
William Townsend
Tenor Networks
100 Nagog Park
Acton, MA 01720
Phone: +1-978-264-4900
Email: btownsend@tenornetworks.com
Thomas D. Nadeau
Cisco Systems, Inc.
250 Apollo Drive
Chelmsford, MA 01824
Le Faucheur et. al 6
ISIS Extensions for Diff-Serv Traffic Engineering Feb 2001
Phone: +1-978-244-3051
Email: tnadeau@cisco.com
Darek Skalecki
Nortel Networks
3500 Carling Ave,
Nepean K2H 8E9
Phone: +1-613-765-2252
Email: dareks@nortelnetworks.com
Le Faucheur et. al 7
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