[Docs] [txt|pdf] [Tracker] [Email] [Nits]

Versions: 00

Internet Draft                                      Paola Iovanna
October 2001                                       Roberto Mameli
Expiration Date: April 2002                   Giovanna Piantanida
                                               Ericsson Lab Italy
                                                  Stefano Salsano
                             CoRiTeL/ Univ. of Rome "Tor Vergata"

Document: draft-iovanna-rsvp-mpls-flowspec-00.txt


           Definition of the MPLS FlowSpec for RSVP-TE


     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 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.

Distribution of this memo is unlimited.



      Abstract

The support of QoS Differentiation in MPLS is based on the definition of
two types of LSP, respectively E-LSP and L-LSP (see [11]). Both E-LSP
and L-LSP can be established with bandwidth reservation. In this case
bandwidth requirements for the LSP must be signaled at LSP establishment
time, in order to perform admission control in the LSRs in the path. If
RSVP-TE is used as setup protocol, it has to support the signaling of
bandwidth requirements for the LSPs. In this document we extend the
RSVP-TE capability by defining a new type of Sender_Tspec (and
FlowSpec), explicitly designed to allow signaling of bandwidth
requirements for E-LSP and L-LSP set up. This new type, called MPLS
Sender_Tspec (MPLS FlowSpec), can include bandwidth requirements for
different classes inside the LSP.




Many folks                Expires April 2002                         1

           Definition of the MPLS FlowSpec for RSVP-TE         Apr-02



     Table of Contents

1. Introduction...............................................3
2. Definition of the MPLS Sender_Tspec (MPLS FlowSpec) object.3
3. Handling of the MPLS Sender_Tspec (MPLS FlowSpec) object in the
DiffServ over MPLS scenario....................................8
4. Security Considerations....................................9
5. IANA Considerations........................................10
6. Acknowledgements...........................................10
7. Example scenario requiring per-OA admission control........10
8. References.................................................11
9. AuthorsÆ Addresses.........................................11



    Acronyms

The reader is assumed to be familiar with the terminology used in this
document. A list of the acronyms used is reported below.


AF              Assured Forwarding
BA              Behavior Aggregate
BE              Best Effort
CLS             Controlled Load Service
CS              Class Selector
DF              Default Forwarding
DSCP            Differentiated Services Code Point
EF              Expedited Forwarding
EXP             EXPerimental (bits)
E-LSP           EXP-inferred-PSC LSP
GS              Guaranteed Service
LSP             Label Switched Path
LSR             Label Switched Router
L-LSP           Label-only-inferred-PSC LSP
MPLS            Multi Protocol Label Switching
OA              Ordered Aggregate
PHB             Per Hop Behavior
PHBID           PHB IDentification code
PSC             Packet Scheduling Class
RSVP-TE RSVP Traffic Engineering extension
SLS             Service Level Specification
TE              Traffic Engineering
Tspec           Traffic specification










Many folks                Expires April 2002                         2

           Definition of the MPLS FlowSpec for RSVP-TE         Apr-02



1. Introduction

MPLS support of Differentiated Services is based on the definition of
two types of LSP (see [11]). They are commonly referred to as L-LSP
(Label-only-inferred-PSC LSP) and E-LSP (EXP-inferred-PSC LSP). L-LSPs
are used to carry traffic belonging to a single OA; they support a
single PSC, explicitly signaled at LSP establishment time, while
additional information useful for the packet treatment (e.g. the drop
precedence) are conveyed by the EXP bits. E-LSPs, instead, are thought
for the support of multiple OAs; in this case the EXP bits in the MPLS
shim header indicate the PHB to be applied to the packet.

Both L-LSP and E-LSP can be established with bandwidth reservation. In
the first case bandwidth requirements for the LSP are signaled at LSP
establishment time; they are used by LSRs along the path to perform
admission control over the provisioned DiffServ resources. The current
specification of RSVP-TE states that bandwidth reservation for both E-
LSP and L-LSP can be obtained by using IntServ Controlled Load Service,
or possibly Guaranteed Service (see [9]); in this case the bandwidth
requirements are signaled in the Sender_Tspec object of the PATH message
(respectively FlowSpec of the RESV message).

This current approach for signaling bandwidth requirements is not
completely satisfactory. First of all it is not correct from a
conceptual point of view; in fact we use an IntServ Sender_Tspec
(respectively IntServ FlowSpec) to signal bandwidth requirements for a
scenario other than Integrated Service. Moreover in the case of E-LSP,
the current specification does not allow to signal bandwidth
requirements separately and independently for the different OAs carried
by the E-LSP (bandwidth specification can only be given on aggregate
basis).

There are some scenarios in which signaling and reservation of resources
on a per-OA basis within an E-LSP could be desirable, e.g. to allow per-
class resource management and admission control (see 7). This document
defines a new type of Sender_Tspec (respectively FlowSpec), explicitly
designed to allow signaling of bandwidth requirements for E-LSP and L-
LSP set up. The new type is called MPLS Sender_Tspec (respectively MPLS
FlowSpec). It supports the signaling of bandwidth requirements for a set
of OAs independently.

The proposed solution applies to the MPLS support of Differentiated
Service as defined in [11], but it can also be used for other scenarios
where a MPLS network supports a set of traffic classes.

2. Definition of the MPLS Sender_Tspec (MPLS FlowSpec) object

In [13] the problem of signaling bandwidth requirements separately for
the different OAs transported over a single E-LSP is examined. As stated
there, at least three possible solutions exist, namely:

    (1)  Creation of a new object;


Many folks                Expires April 2002                         3

           Definition of the MPLS FlowSpec for RSVP-TE         Apr-02


    (2)  Extension of the existing DiffServ object (defined in [11]);
    (3)  Extension of the existing Sender_Tspec (FlowSpec) to signal
         multiple FlowSpecs.

The first approach is the one followed in [13]; it consists in the
creation of the new ELSP object at the purpose of signaling bandwidth
requirements per OA. The second approach seems to be the least
desirable, for several reasons. First of all, it would change the
original meaning of the DiffServ object, on a second-hand it would be
applicable only in the DiffServ over MPLS scenario and finally it would
require the DiffServ object to be present in the RESV message.

In this document, instead, we propose to follow the third approach, i.e.
to extend the existing Sender_Tspec (FlowSpec) with the introduction of
a new C-Type. This is motivated by several reasons: first of all the
introduction of a new Sender_Tspec (FlowSpec) type is more correct from
a conceptual point of view. In fact it allows preserving the
functionality of the Sender_Tspec (FlowSpec), since it keeps its
original meaning of signaling traffic characteristics (with a finer
granularity level of the reservation, i.e. on a per-OA basis).
In addition the new object type can be used for both E-LSP and L-LSP,
and also for QoS over MPLS scenarios other than DiffServ. It can be
designed in a flexible way, in order to allow signaling of bandwidth
requirements in different ways, i.e. in accordance to different traffic
models (possibly not only based on Tspec).
Moreover the coexistence between a new object for bandwidth reservation
(as proposed by the first solution) and the current Sender_Tspec
(FlowSpec) object could lead to conflicts.
Finally the introduction of a new C-Type does not raise particular
problems in terms of backward compatibility with existing
implementations that do not support it.

The following paragraph describes the object in more details.


2.1    MPLS Sender_Tspec (MPLS FlowSpec)

In this section the structure of the new MPLS Sender_Tspec (FlowSpec)
type is defined. It is exactly the same in both cases, with the obvious
difference of the Class value.

Class  =  9  (FlowSpec class)
Class  = 12  (Sender_Tspec class)

C-type =  3  (MPLS Sender_Tspec/FlowSpec object)

The content and the encoding rules for this object are specified in the
following.


   <MPLS Tspec > ::= <MPLS Tspec Header>
                     [<MPLS Tspec Body>]



Many folks                Expires April 2002                         4

           Definition of the MPLS FlowSpec for RSVP-TE         Apr-02


<MPLS Tspec Body> ::= <List of MPLS Tspec SubObjects>

   <List of MPLS Tspect SubObjects ::= <MPLS Tspec SubObject>   |
                                       <MPLS Tspec SubObject>
                                       <List of MPLS Tspec SubObjects>

   <MPLS Tspec SubObject> :== <MPLS Tspec SubObject header>
                              <MPLS Tspec SubObject body>



   <MPLS Tspec Header>

                        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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Version     |     Flags     |   Reserved    | Num-of-SubObjs|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Version: 8 bits
          It specifies the version of the object and it is used for
          future extensions. Current value for Version is 1.

  Flags: 8 bits
          Can be used to define flags. Currently set to 0.

  Reserved: 8 bits
          Set to 0.

  Num-of-SubObjs: 8 bits
          Specifies the number of SubObjects in the the MPLS Tspec Body.
          In the case of absence of the MPLS Tspec Body, this is set to
          0. This means that no bandwidth reservation is related to the
          LSP setup.



   <MPLS Tspec object header>

                        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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  SubObj-num   |            Reserved           |    Length     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     SubObj-num: 8 bits
          Specifies the type of SubObject. Currently two types of
          SubObjects are defined:

               SubObj-num = 1 : OA-Traffic Profile PHBID

               SubObj-num = 2 : OA-Traffic Profile Simple Exp



Many folks                Expires April 2002                         5

           Definition of the MPLS FlowSpec for RSVP-TE         Apr-02


          OA-TP PHBID SubObject will be used in the MPLS/Diffserv
          scenario.

     Reserved: 16 bits
          Currently set to 0. It could contain SubObj specific
          information.

     Length: 8 bits
          Specifies the length of the SubObject body in 32bit words.



The <MPLS Tspec object body> is specific for each SubObj-num as follows:


<MPLS Tspec SubObject body> for OA-Traffic Profile PHBID

                        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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             PHBID             |   TP-style    |    Length     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Traffic Profile Parameter                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //                        . . . . . . .                        //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Traffic Profile Parameter                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



<MPLS Tspec SubObject body> for OA-Traffic Profile Simple Exp

                        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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Exp |         Reserved        |   TP-style    |    Length     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Traffic Profile Parameter                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //                        . . . . . . .                        //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Traffic Profile Parameter                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


  Length: 8 bits
          This field indicates the length of the <MPLS Tspec SubObject
          body> in 32 bit words.

  PHBID: 16 bits
          This field contains the Per Hop Behavior Identification Code,
          encoded as specified in [12].


Many folks                Expires April 2002                         6

           Definition of the MPLS FlowSpec for RSVP-TE         Apr-02



  Exp: 3 bits
          This field contains the Exp field.

  TP-Style: 8 bits
          This field indicates the bandwidth requirement type. Different
          representations for the bandwidth requirements can be used,
          according to the traffic models available. Currently two
          possible TP-Style values are defined, but other values could
          be introduced in the future if needed.

          TP-style = 1  (Tspec parameters as defined for RSVP)

    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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Token Bucket Rate [r] (32-bit IEEE floating point number)    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Token Bucket Size [b] (32-bit IEEE floating point number)    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Peak Data Rate [p] (32-bit IEEE floating point number)       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Minimum Policed Unit [m] (32-bit integer)                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Maximum Packet Size [M]  (32-bit integer)                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

          TP-style = 2  (Simple bandwidth parameter)

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |    Bandwidth     [b]   (32-bit IEEE floating point number)    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



An example of a complete MPLS Sender Tspec object is given hereafter. It
represents the bandwidth requirements for an E-LSP which supports two
OA. Therefore, it includes the bandwidth requirements for two different
PHBIDs, respectively expressed with a Token Bucket representation and
with a Simple bandwidth parameter.













Many folks                Expires April 2002                         7

           Definition of the MPLS FlowSpec for RSVP-TE         Apr-02


Example of a complete MPLS Tspec object

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Length (bytes)       |  C-Num=12     |    C-Type=3   |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |   Version=1   |    Flags=0    |   Reserved    |Num-of-SubObj=2|
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | SubObj-num=1  |          Reserved             |  Length=6     |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          PHBID= xx            |  TP-style=1   |  Length=5     |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Token Bucket Rate [r] (32-bit IEEE floating point number)    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Token Bucket Size [b] (32-bit IEEE floating point number)    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Peak Data Rate [p] (32-bit IEEE floating point number)       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Minimum Policed Unit [m] (32-bit integer)                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Maximum Packet Size [M]  (32-bit integer)                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | SubObj-num=1  |          Reserved             |  Length=2     |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          PHBID= yy            |  TP-style=2   |  Length=1     |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |    Bandwidth     [b]   (32-bit IEEE floating point number)    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




3. Handling of the MPLS Sender_Tspec (MPLS FlowSpec) object in the
   DiffServ over MPLS scenario

This paragraph describes in details all the operations related to the
new Sender_Tspec (FlowSpec) handling in the particular scenario of
DiffServ over MPLS. In this case the object is intended to support
signaling of bandwidth requirements on a per-OA basis for both E-LSP and
L-LSP. However, for backward compatibility, Sender_Tspec (FlowSpec)
objects with IntServ C-type can still be used in PATH (RESV) messages to
signal bandwidth requirements for the entire flow, as specified in [9]
and [11]. It is worth to observe that in the case of L-LSP the new MPLS
C-type does not add new information with respect to the classical
IntServ C-type; in fact there is no need to signal per-OA bandwidth
requirements in such situations. Nevertheless the use of the MPLS
Sender_Tspec (FlowSpec) is preferred for at least two reasons. First it
is more correct from a conceptual point of view, as stated before, and
second it allows signaling such bandwidth requirements in a more
flexible way (e.g. representing only the bandwidth value instead of the
5-tuple Tspec).



Many folks                Expires April 2002                         8

           Definition of the MPLS FlowSpec for RSVP-TE         Apr-02


A node that receives a PATH (RESV) message containing a MPLS
Sender_Tspec (FlowSpec) but does not support it, must generate a PATH
ERR (RESV ERR) message corresponding to ôUnknown object C-Typeö (Error
Code = 14, see Appendix B of [1]).

To signal per-OA traffic requirements the ingress LSR must include a
MPLS Sender_Tspec object in the PATH message. Correspondingly the
receiver must include a MPLS FlowSpec object in the RESV message.

Each PSC signaled in the MPLS Sender_Tspec (MPLS FlowSpec) must be
supported. In the case of E-LSP a corresponding set of EXP<->PHB mapping
must exist. Of course this means that all the PHB associated to each PSC
signaled in the MPLS Sender_Tspec (FlowSpec) must be supported, either
pre-configured on every node or signaled by means of the DIFFSERV object
([11]). In the case of L-LSP the Encaps<->PHB mapping specified in the
DIFFSERV object must coincide with the PSC signaled in the MPLS
Sender_Tspec (FlowSpec) (Of course for a L-LSP this object must include
only a single SubObject).

A node that receives a PATH (RESV) message with MPLS Sender_Tspec
(FlowSpec) object containing one or more unsupported PSC must fail the
reservation request and send a PATH_ERR (RESV ERR) message of the type
ôDiff-Serv Errorö (Error code to be assigned by the IANA, see section
5.5 of [11]) and error value 2 (ôUnsupported PHBö) or 4 (ôUnsupported
PSCö).

A node that receives a RESV message with per-OA traffic profiles
signaled in the MPLS FlowSpec object must perform Admission Control on
every aggregate. If resources available for one or more OA signaled in
MPLS FlowSpec are deemed insufficient, the node must fail the entire
resource reservation. In this case it must send a RESV_ERR message with
Error Code = 01 (ôAdmission Control Failureö) and Error Value of the
form 0000cccccccccccc (ôAdmission Control Failure for an OAö, TBD).

If all the PHB/PSC signaled in the MPLS Sender_Tspec (MPLS FlowSpec) are
supported and sufficient resources are available for each of them, then
the node must carry out proper actions in order to let the reservation
succeed (i.e. proper configuration of schedulers, classifiers and
traffic conditioning elements).

A node must handle all the situations where a LSP cannot be accepted for
other reason than the ones discussed in this section, in accordance to
[1], [9] and [11].



4. Security Considerations

This document does not introduce additional security issues beyond those
discussed in [1], [3], [7], [9] and [11]. As a consequence it may use
the same mechanisms described in the references above.




Many folks                Expires April 2002                         9

           Definition of the MPLS FlowSpec for RSVP-TE         Apr-02



5. IANA Considerations

This document defines a new object type with implications for IANA. A
new C-type is defined for the MPLS Sender_Tspec (MPLS FlowSpec) object.
The value (C-type = 3) has been chosen according to the First Come First
Served policy defined in [14].

The new RSVP error code (ôDiffServ Errorö) should also be assigned from
IANA (see section 5.5 of [11]). Finally a new error sub-code related to
the ôAdmission Control Failureö error must be assigned.



6. Acknowledgements

Authors would like to thank all the people that participated to the
revision of this document contributing with comments and suggestions.



7. Example scenario requiring per-OA admission control

There are many scenarios in which an MPLS network could support
Differentiated Services by means of E-LSP. In such cases the provider
would like to give service differentiation in its traffic engineered
network without the complexity of managing different L-LSP for different
services. Even if the provider is not interested in complex traffic
engineering functionality (e.g. per class routing or per class
protection/restoration), nevertheless it could be useful to manage
resources on a per-OA basis, in order to allow better service
provisioning and increased efficiency in network utilization.

For example, consider an ISP network that provides only two classes of
service (e.g. Best Effort and Premium) using E-LSP. Assume that a
generic node within the network is connected to a link with 100Mbit
total bandwidth; assume it is able to provide 20Mbit of its bandwidth to
Premium Service and the remaining 80Mbit to Best Effort traffic. Now
imagine that the node receives two requests for E-LSP setup: E-LSP A and
E-LSP B.

  - E-LSP A requires 40Mbit of the link bandwidth (respectively
    15Mbit for Premium Service and 25Mbit for Best Effort)
  - E-LSP B requires 50Mbit of the link bandwidth (respectively
    15Mbit for Premium Service and 35Mbit for Best Effort)

If the node does not support the MPLS Sender_Tspec (MPLS FlowSpec)
extension described in this document, then it cannot perform per-OA
admission control. In this case admission control is performed on
aggregate basis. Since the total bandwidth requirement of the two E-LSPs
is less than the link bandwidth, they are both accepted (90Mbit of link
bandwidth, respectively 30Mbit for Premium Service and 60Mbit for Best
Effort). Note however that the total amount of Premium traffic exceeds


Many folks                Expires April 2002                        10

           Definition of the MPLS FlowSpec for RSVP-TE         Apr-02


the pre-configured limit (set to 20Mbit) and, as a consequence, Premium
traffic on both E-LSP will be adversely affected.

In contrast, if the new object is supported and per-OA based Admission
Control is performed, the node rejects one of the requests because it is
able to control the bandwidth availability for each class of service.
Upon rejection the network can react in various ways, from the simple
choice of rerouting to more complex actions, such as resource
provisioning and redistribution.



8. References

[1]    R. Braden et al., ôResource Reservation Protocol (RSVP) û
    Version 1, Functional Specificationö, RFC 2205, September 1997
[2]    J. Wroclawsky, ôThe use of RSVP with IETF Integrated Servicesö,
    RFC 2210, September 1997
[3]    R. Braden et al., ôResource Reservation Protocol (RSVP) û
    Version 1 Message Processing Rulesö, RFC 2209, September 1997
[4]    J. Wroclawsky, ôSpecification of the Controlled-Load Network
    Element Serviceö, RFC 2211, September 1997
[5]    S. Shenker et al., ôSpecification of Guaranteed Quality of
    Serviceö, RFC 2212, September 1997
[6]    Y. Bernet et al., ôSpecification of the Null Service Typeö, RFC
    2997, November 2000
[7]    E. Rosen et al., ôMultiprotocol Label Switching Architectureö,
    RFC 3031, January 2001
[8]    D. Awduche et al., ôRequirements for Traffic Engineering over
    MPLSö, RFC 2702, September 1999
[9]    D. Awduche et al., ôRSVP-TE: Extensions to RSVP for LSP
    Tunnelsö, draft-ietf-mpls-rsvp-lsp-tunnel-09.txt, February 2001
[10]   D. Awduche et al., ôApplicability Statement for Extensions to
    RSVP for LSP-Tunnelsö, draft-ietf-mpls-rsvp-tunnel-applicability-
    02.txt, April 2001
[11]   F. Le Faucheur et al., ôMPLS Support of Differentiated
    Servicesö, draft-ietf-mpls-diff-ext-09.txt, April 2001
[12]   D.Black et al., ôPer Hop Behavior Identification Codeö, RFC
    3140, June 2001
[13]   S. Ganti et al., ôMPLS Support of Differentiated Services using
    E-LSPö, draft-ganti-mpls-diffserv-elsp-00.txt, April 2001
[14]   T. Narten et al., ôGuidelines for writing an IANA Considerations
    Section in RFCsö, RFC 2434, October 1998



9. AuthorsÆ Addresses

Paola Iovanna
Ericsson Lab Italy S.p.A.
Via Anagnina 203
00040 - Morena (Rome) û Italy
Tel.    +39 06 72582814


Many folks                Expires April 2002                        11

           Definition of the MPLS FlowSpec for RSVP-TE         Apr-02


E-mail: paola.iovanna@eri.ericsson.se

Roberto Mameli
Ericsson Lab Italy S.p.A.
Via Anagnina 203
00040 - Morena (Rome) û Italy
Tel.    +39 06 72589119
E-mail: roberto.mameli@eri.ericsson.se

Giovanna Piantanida
Ericsson Lab Italy S.p.A.
Via Anagnina 203
00040 - Morena (Rome) û Italy
Tel.    +39 06 72583537
E-mail: giovanna.piantanida@eri.ericsson.se

Stefano Salsano
University of Rome Tor Vergata
CoRiTeL û Consorzio di Ricerca sulle Telecomunicazioni
c/o Ericsson - Via Anagnina 203
00040 - Morena (Rome) û Italy
Tel.    +39 06 72582540
E-mail: salsano@coritel.it
































Many folks                Expires April 2002                        12


Html markup produced by rfcmarkup 1.123, available from https://tools.ietf.org/tools/rfcmarkup/