draft-ietf-mpls-crlsp-modify-03.txt   rfc3214.txt 
MPLS WG J. Ash
Internet Draft AT&T
Document: draft-ietf-mpls-crlsp-modify-03.txt
Y. Lee
Iris Labs
P. Ashwood-Smith Network Working Group J. Ash
B. Jamoussi Request for Comments: 3214 AT&T
D. Fedyk Category: Standards Track Y. Lee
D. Skalecki Ceterus Networks
Nortel Networks P. Ashwood-Smith
B. Jamoussi
L. Li D. Fedyk
SS8 Networks D. Skalecki
Nortel Networks
March, 2001 L. Li
Expires: September 2001 SS8 Networks
January 2002
LSP Modification Using CR-LDP LSP Modification Using CR-LDP
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document specifies an Internet standards track protocol for the
all provisions of Section 10 of RFC2026 [1]. Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Internet-Drafts are working documents of the Internet Engineering Copyright Notice
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1. Abstract Copyright (C) The Internet Society (2002). All Rights Reserved.
After a CR-LSP is set up, its bandwidth reservation may need to be Abstract
changed by the network operator, due to the new requirements for the
traffic carried on that CR-LSP [2]. This contribution presents an This document presents an approach to modify the bandwidth and
approach to modify the bandwidth and possibly other parameters of an possibly other parameters of an established CR-LSP (Constraint-based
established CR-LSP using CR-LDP [3] without service interruption. Routed Label Switched Paths) using CR-LDP (Constraint-based Routed
The LSP modification feature can be supported by CR-LDP by use of Label Distribution Protocol) without service interruption. After a
the _modify_ value for the _action indicator flag_ in the LSPID TLV CR-LSP is set up, its bandwidth reservation may need to be changed by
[3]. This feature has application in dynamic network resources the network operator, due to the new requirements for the traffic
management where traffic of different priorities and service classes carried on that CR-LSP. The LSP modification feature can be
is involved. supported by CR-LDP by use of the _modify_value for the _action
indicator flag_ in the LSPID TLV. This feature has application in
dynamic network resources management where traffic of different
priorities and service classes is involved.
Table of Contents Table of Contents
1. Abstract 1. Conventions Used in This Document ............................ 2
2. Conventions Used in This Document 2. Introduction ................................................. 2
3. Introduction 3. LSP Modification Using CR-LDP ................................ 3
4. LSP Modification Using CR-LDP 3.1 Basic Procedure for Resource Modification .................. 3
4.1 Basic Procedure for Resource Modification 3.2 Rerouting LSPs ............................................. 5
4.2 Rerouting LSPs 3.3 Priority Handling .......................................... 6
4.3 Priority Handling 3.4 Modification Failure Case Handling ......................... 6
4.4 Modification Failure Case Handling 4. Application of LSP Bandwidth Modification in Dynamic Resource
5. Application of LSP Bandwidth Modification in Dynamic Resource Management ................................................... 7
Management 5. Acknowledgments .............................................. 8
6. Acknowledgments 6. Intellectual Property Considerations ......................... 8
7. Intellectual Property Considerations 7. Security Considerations ...................................... 8
8. Security Considerations 8. References ................................................... 8
9. References 9. Authors' Addresses ........................................... 9
10. Authors' Addresses 10. Full Copyright Statement ..................................... 11
2. Conventions Used in This Document 1. Conventions Used in This Document
L: LSP (Label Switched Path) L: LSP (Label Switched Path)
L-id: LSPID (LSP Identifier) L-id: LSPID (LSP Identifier)
T: Traffic Parameters T: Traffic Parameters
R: LSR (Label Switching Router) R: LSR (Label Switching Router)
FEC: Forwarding Equivalence Class FEC: Forwarding Equivalence Class
NHLFE: Next Hop Label Forwarding Entity NHLFE: Next Hop Label Forwarding Entry
FTN: FEC To NHLFE FTN: FEC To NHLFE
TLV: Type Length Value TLV: Type Length Value
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
this document are to be interpreted as described in RFC-2119 [4]. document are to be interpreted as described in RFC 2119 [4].
3. Introduction 2. Introduction
Consider an LSP L1 that has been established with its set of traffic Consider an LSP L1 that has been established with its set of traffic
parameters T0. A certain amount of bandwidth is reserved along the parameters T0. A certain amount of bandwidth is reserved along the
path of L1. Consider then that some changes are required on L1. For path of L1. Consider then that some changes are required on L1. For
example, the bandwidth of L1 needs to be increased to accommodate example, the bandwidth of L1 needs to be increased to accommodate the
the increased traffic on L1. Or the SLA associated with L1 needs to increased traffic on L1. Or the SLA associated with L1 needs to be
be modified because a different service class is desired. The modified because a different service class is desired. The network
network operator, in these cases, would like to modify the operator, in these cases, would like to modify the characteristics of
characteristics of L1, for example, to change its traffic parameter L1, for example, to change its traffic parameter set from T0 to T1,
set from T0 to T1, without releasing the LSP L1 to interrupt the without releasing the LSP L1 to interrupt the service. In some other
service. In some other cases, network operators may want to reroute cases, network operators may want to reroute a CR-LSP to a different
a CR-LSP to a different path for either improved performance or path for either improved performance or better network resource
better network resource utilization. In all these cases, LSP utilization. In all these cases, LSP modification is required. In
modification is required. In section 4 below, a method to modify an section 3 below, a method to modify an active LSP using CR-LDP is
active LSP using CR-LDP is presented. The concept of LSPID in CR-LDP presented. The concept of LSPID in CR-LDP is used to achieve the LSP
is used to achieve the LSP modification, without releasing the LSP modification, without releasing the LSP and interrupting the service
and interrupting the service and, without double booking the and, without double booking the bandwidth. In Section 4, an example
bandwidth. In Section 5, an example is described to demonstrate an is described to demonstrate an application of the presented method in
application of the presented method in dynamically managing network dynamically managing network bandwidth requirements without
bandwidth requirements without interrupting service. In CR-LDP, an interrupting service. In CR-LDP, an action indicator flag of
action indicator flag of _modify_ is used in order to explicitly _modify_ is used in order to explicitly specify the behavior, and
specify the behavior, and allow the existing LSPID to support other allow the existing LSPID to support other networking capabilities in
networking capabilities in the future. Reference [3], the future. Reference [3], RFC XXXX, specifies the action indicator
<draft-ietf-mpls-cr-ldp-03.txt>, specifies the action indicator flag flag of _modify_ for CR-LDP.
of _modify_ for CR-LDP.
4. LSP Modification Using CR-LDP 3. LSP Modification Using CR-LDP
4.1 Basic Procedure for Resource Modification 3.1 Basic Procedure for Resource Modification
LSP modification can only be allowed when the LSP is already set up LSP modification can only be allowed when the LSP is already set up
and active. That is, modification is not defined nor allowed during and active. That is, modification is not defined nor allowed during
the LSP establishment or label release/withdraw phases. Only the LSP establishment or label release/withdraw phases. Only
modification requested by the ingress LSR of the LSP is considered modification requested by the ingress LSR of the LSP is considered in
in this draft for CR-LSP. The Ingress LSR cannot modify an LSP before this document for CR-LSP. The Ingress LSR cannot modify an LSP
a previous modification procedure is completed. before a previous modification procedure is completed.
Assume that CR-LSP L1 is set up with LSPID L-id1, which is unique in Assume that CR-LSP L1 is set up with LSPID L-id1, which is unique in
the MPLS network. The ingress LSR R1 of L1 has in its FTN (FEC To the MPLS network. The ingress LSR R1 of L1 has in its FTN (FEC To
NHLFE) table FEC1 -> Label A mapping where A is the outgoing label NHLFE) table FEC1 -> Label A mapping where A is the outgoing label
for LSP L1. To modify the characteristics of L1, R1 sends a Label for LSP L1. To modify the characteristics of L1, R1 sends a Label
Request Message. In the message, the TLVs will have the new Request Message. In the message, the TLVs will have the new
requested values, and the LSPID TLV is included which indicates the requested values, and the LSPID TLV is included which indicates the
value of L-id1. The Traffic Parameters TLV, the ER-TLV, the Resource value of L-id1. The Traffic Parameters TLV, the ER-TLV, the Resource
Class (color) TLV and the Preemption TLV can have values different Class (color) TLV and the Preemption TLV can have values different
from those in the original Label Request Message, which has been from those in the original Label Request Message, which has been
used to set up L1 earlier. Thus, L1 can be changed in its bandwidth used to set up L1 earlier. Thus, L1 can be changed in its bandwidth
request (traffic parameter TLV), its traffic service class (traffic request (traffic parameter TLV), its traffic service class (traffic
parameter TLV), the route it traverses (ER TLV) and its setup and parameter TLV), the route it traverses (ER TLV) and its setup and
holding (Preemption TLV) priorities. The ingress LSR R1 now still holding (Preemption TLV) priorities. The ingress LSR R1 now still has
has the entry in its FTN as FEC1 -> Label A. R1 is waiting to the entry in its FTN as FEC1 -> Label A. R1 is waiting to establish
establish another entry for FEC1. another entry for FEC1.
When an LSR Ri along the path of L1 receives the Label Request When an LSR Ri along the path of L1 receives the Label Request
message, its behavior is the same as that of receiving any Label message, its behavior is the same as that of receiving any Label
request message. The only extension is that Ri examines the LSPID request message. The only extension is that Ri examines the LSPID
carried in the Label Request Message, L-id1, and identifies if it carried in the Label Request Message, L-id1, and identifies if it
already has L-id1. If Ri does not have L-id1, Ri behaves the same as already has L-id1. If Ri does not have L-id1, Ri behaves the same as
receiving a new Label Request message. If Ri already has L-id1, Ri receiving a new Label Request message. If Ri already has L-id1, Ri
takes the newly received Traffic Parameter TLV and computes the new takes the newly received Traffic Parameter TLV and computes the new
bandwidth required and derives the new service class. Compared with bandwidth required and derives the new service class. Compared with
the already reserved bandwidth for L-id1, Ri now reserves only the the already reserved bandwidth for L-id1, Ri now reserves only the
difference of the bandwidth requirements. This prevents Ri from difference of the bandwidth requirements. This prevents Ri from doing
doing bandwidth double booking. If a new service class is requested, bandwidth double booking. If a new service class is requested, Ri
Ri also prepares to receive the traffic on L1 in just the same way as also prepares to receive the traffic on L1 in just the same way as
handling it for a Label Request Message, perhaps using a different handling it for a Label Request Message, perhaps using a different
type of queue. Ri assigns a new label for the Label Request Message. type of queue. Ri assigns a new label for the Label Request Message.
When the Label Mapping message is received, two sets of labels exist When the Label Mapping message is received, two sets of labels exist
for the same LSPID. Then the ingress LSR R1 will have two outgoing for the same LSPID. Then the ingress LSR R1 will have two outgoing
labels, A and B, associated with the same FEC, where B is the new labels, A and B, associated with the same FEC, where B is the new
outgoing label received for LSP L1. The ingress LSR R1 can now outgoing label received for LSP L1. The ingress LSR R1 can now
activate the new entry in its FTN, FEC1 - > Label B. This means that activate the new entry in its FTN, FEC1 - > Label B. This means that
R1 swaps traffic on L1 to the new label _B_ (_new_ path) for L1. The R1 swaps traffic on L1 to the new label _B_ (_new_ path) for L1. The
packets can now be sent with the new label B, with the new set of packets can now be sent with the new label B, with the new set of
skipping to change at line 176 skipping to change at page 4, line 31
will be sent out with the new outgoing label. The LSRs do not have will be sent out with the new outgoing label. The LSRs do not have
to implement new procedures to track the new and old characteristics to implement new procedures to track the new and old characteristics
of the LSP. of the LSP.
The ingress LSR R1 then starts to release the original label A for The ingress LSR R1 then starts to release the original label A for
LSP L1. The Label Release Message is sent by R1 towards the down LSP L1. The Label Release Message is sent by R1 towards the down
stream LSRs. The Release message carries the LSPID of L-id1 and the stream LSRs. The Release message carries the LSPID of L-id1 and the
Label TLV to indicate which label is to be released. The Release Label TLV to indicate which label is to be released. The Release
Message is propagated to the egress LSR to release the original Message is propagated to the egress LSR to release the original
labels previously used for L1. Upon receiving the Label Release labels previously used for L1. Upon receiving the Label Release
Message, LSR Ri examines the LSPID, L-id1, and finds out that the Message, LSR Ri examines the LSPID, L-id1, and finds out that the L-
L-id1 has still another set of labels (incoming/outgoing) under it. id1 has still another set of labels (incoming/outgoing) under it.
Thus, the old label is released without releasing the resource in Thus, the old label is released without releasing the resource in
use. That is, if the bandwidth has been decreased for L1, the delta use. That is, if the bandwidth has been decreased for L1, the delta
bandwidth is released. Otherwise, no bandwidth is released. This bandwidth is released. Otherwise, no bandwidth is released. This
modification procedure can not only be applied to modify the traffic modification procedure can not only be applied to modify the traffic
parameters and/or service class of an active LSP, but also to parameters and/or service class of an active LSP, but also to reroute
reroute an existing LSP (as described in Section 4.2 below), and/or an existing LSP (as described in Section 3.2 below), and/or change
change its setup/holding priority if desired. After the release its setup/holding priority if desired. After the release procedure,
procedure, the modification of the LSP is completed. the modification of the LSP is completed.
The method described above follows the normal behavior of Label The method described above follows the normal behavior of Label
Request / Mapping / Notification / Release / Withdraw procedure of a Request / Mapping / Notification / Release / Withdraw procedure of a
CR-LDP operated LSR with a specific action taken on an LSPID. If a CR-LDP operated LSR with a specific action taken on an LSPID. If a
Label Withdraw Message is used to withdraw a label associated with an Label Withdraw Message is used to withdraw a label associated with an
LSPID, the Label TLV should be included to specify which label to LSPID, the Label TLV should be included to specify which label to
withdraw. Since the LSPID can also be used for other feature withdraw. Since the LSPID can also be used for other feature
support, an action indication flag of _modify_ assigned to the LSPID support, an action indication flag of _modify_ assigned to the LSPID
would explicitly explain the action/semantics that should be would explicitly explain the action/semantics that should be
associated with the messaging procedure. The details of this flag associated with the messaging procedure. The details of this flag
are addressed in the CR-LDP draft, Reference [3]. are addressed in the CR-LDP document, Reference [3].
4.2 Rerouting LSPs 3.2 Rerouting LSPs
LSP modification can also be used to reroute an existing LSP. Only LSP modification can also be used to reroute an existing LSP. Only
modification requested by the ingress LSR of the LSP is considered modification requested by the ingress LSR of the LSP is considered in
in this draft for CR-LSP. The Ingress LSR cannot modify an LSP before this document for CR-LSP. The Ingress LSR cannot modify an LSP before
a previous modification procedure is completed. a previous modification procedure is completed.
As in the previous section, consider a CR-LSP L1 with LSPID L-id1. As in the previous section, consider a CR-LSP L1 with LSPID L-id1.
To modify the route of the LSP, the ingress LSR R1 sends a Label To modify the route of the LSP, the ingress LSR R1 sends a Label
Request Message. In the message, the LSPID TLV indicates L-id1 and Request Message. In the message, the LSPID TLV indicates L-id1 and
the Explicit Route TLV is specified with some different hops from the Explicit Route TLV is specified with some different hops from the
the explicit route specified in the original Label Request Message. explicit route specified in the original Label Request Message. The
The action indication flag has the value _modify_. action indication flag has the value _modify_.
At this point, the ingress LSR R1 still has an entry in FTN as At this point, the ingress LSR R1 still has an entry in FTN as
FEC1 -> Label A. R1 is waiting to establish another entry for FEC1. FEC1 -> Label A. R1 is waiting to establish another entry for FEC1.
When an LSR Ri along the path of L1 receives the Label Request When an LSR Ri along the path of L1 receives the Label Request
message, its behavior is the same as that of receiving a Label message, its behavior is the same as that of receiving a Label
Request Message that modifies some other parameters of the LSP. Request Message that modifies some other parameters of the LSP. Ri
Ri assigns a new label for the Label Request Message and forwards assigns a new label for the Label Request Message and forwards the
the message along the explicit route. It does not allocate any message along the explicit route. It does not allocate any more
more resources except as described in section 4.1. resources except as described in section 3.1.
At another LSR Rj further along the path, the explicit route At another LSR Rj further along the path, the explicit route diverges
diverges from the previous route. Rj acts as Ri, but forwards the from the previous route. Rj acts as Ri, but forwards the Label
Label Request message along the new route. From this point onwards Request message along the new route. From this point onwards the
the Label Request Message is treated as setting up a new LSP by Label Request Message is treated as setting up a new LSP by each LSR
each LSR until the paths converge at later LSR Rk. The _modify_ until the paths converge at later LSR Rk. The _modify_ value of the
value of the action indication flag is ignored. action indication flag is ignored.
At Rk and subsequent LSRs, the Label Request Message is handled as At Rk and subsequent LSRs, the Label Request Message is handled as at
at Ri. Ri.
On the return path, when the Label Mapping message is received, two On the return path, when the Label Mapping message is received, two
sets of labels for the LSPID exist where the new route coincide sets of labels for the LSPID exist where the new route coincide with
with the old. Only one set of labels will exist at LSRs where the the old. Only one set of labels will exist at LSRs where the routes
routes diverge. diverge.
When the Label Mapping message is received at the ingress LSR R1 it When the Label Mapping message is received at the ingress LSR R1 it
has two outgoing labels, A and B, associated with the same has two outgoing labels, A and B, associated with the same FEC, where
FEC, where B is the new outgoing label received for LSP L1. R1 can B is the new outgoing label received for LSP L1. R1 can now activate
now activate the new entry in the FTN, FEC1 - > Label B and the new entry in the FTN, FEC1 - > Label B and de-activate the old
de-activate the old entry FEC1 - > Label A. This means that R1 entry FEC1 - > Label A. This means that R1 swaps traffic on L1 to the
swaps traffic on L1 to the new label B. The packets are now sent new label B. The packets are now sent with the new label B, on the
with the new label B, on the new path. new path.
The ingress LSR R1 then starts to release the original label A for The ingress LSR R1 then starts to release the original label A for
LSP L1. The Label Release Message is sent by R1 towards the down LSP L1. The Label Release Message is sent by R1 towards the down
stream LSRs following the original route. The Release message stream LSRs following the original route. The Release message carries
carries the LSPID of L-id1 and the Label TLV to indicate which the LSPID of L-id1 and the Label TLV to indicate which label is to be
label is to be released. At each LSR the old label is released - no released. At each LSR the old label is released - no further action
further action is required to change the path of the data packets is required to change the path of the data packets which are already
which are already following the new route programmed by the Label following the new route programmed by the Label Mapping message.
Mapping message.
At some LSRs, where the routes diverged, there is only one label At some LSRs, where the routes diverged, there is only one label for
for the LSPID. For example, between Rj and Rk, the Label Release the LSPID. For example, between Rj and Rk, the Label Release Message
Message will follow the old route. At LSRs between Rj and Rk only will follow the old route. At LSRs between Rj and Rk only the labels
the labels from the original route will exist for LSPID L-id1. At from the original route will exist for LSPID L-id1. At these LSRs
these LSRs the LSPID TLV does not need to be examined to release the the LSPID TLV does not need to be examined to release the correct
correct label, but it must still be updated and passed on to the label, but it must still be updated and passed on to the next LSR as
next LSR as the Label Release message is propagated. In this way, at the Label Release message is propagated. In this way, at Rk where the
Rk where the routes converge, the downstream LSR will know which routes converge, the downstream LSR will know which label to release
label to release and can continue to forward the Label Release and can continue to forward the Label Release Message along the old
Message along the old route. route.
4.3 Priority Handling 3.3 Priority Handling
When sending a Label Request Message for an active LSP L1 to request When sending a Label Request Message for an active LSP L1 to request
changes, the setup priority used in the label Request Message can be changes, the setup priority used in the label Request Message can be
different from the one used in the previous Label Request Message, different from the one used in the previous Label Request Message,
effectively indicating the priority of this _modification_ request. effectively indicating the priority of this _modification_ request.
Network operators can use this feature to decide what priority is to Network operators can use this feature to decide what priority is to
be assigned to a modification request, based on their be assigned to a modification request, based on their
policies/algorithms and other traffic situations in the network. For policies/algorithms and other traffic situations in the network. For
example, the priority for modification can be determined by the example, the priority for modification can be determined by the
priority of the customer/LSP. If a customer has exceeded the priority of the customer/LSP. If a customer has exceeded the
reserved bandwidth of its VPN LSP tunnel by too much, the reserved bandwidth of its VPN LSP tunnel by too much, the
modification request's priority may be given as a higher value. modification request's priority may be given as a higher value. The
The Label Request message for the modification of an active LSP can Label Request message for the modification of an active LSP can also
also be sent with a holding priority different from its previous be sent with a holding priority different from its previous one.
one. This effectively changes the holding priority of the LSP. This effectively changes the holding priority of the LSP. Upon
Upon receiving a Label Request Message that requests a new holding receiving a Label Request Message that requests a new holding
priority, the LSR assigns the new holding priority to the bandwidth. priority, the LSR assigns the new holding priority to the bandwidth.
That is, the new holding priority is assigned to both the existing That is, the new holding priority is assigned to both the existing
incoming / outgoing labels and the new labels to be established for incoming / outgoing labels and the new labels to be established for
the LSPID in question. In this way self-bumping is prevented. the LSPID in question. In this way self-bumping is prevented.
4.4 Modification Failure Case Handling 3.4 Modification Failure Case Handling
A modification attempt may fail due to insufficient resource or A modification attempt may fail due to insufficient resource or other
other situations. A Notification message is sent back to the ingress situations. A Notification message is sent back to the ingress LSR
LSR R1 to indicate the failure of Label Request Message that R1 to indicate the failure of Label Request Message that intended to
intended to modify the LSP. A retry may be attempted if desired by modify the LSP. A retry may be attempted if desired by the network
the network operator. If the LSP on the original path failed when a operator. If the LSP on the original path failed when a modification
modification attempt is in progress, the attempt should be aborted by attempt is in progress, the attempt should be aborted by using the
using the Label Abort Request message as specified in the LDP draft Label Abort Request message as specified in the LDP document [5].
[5].
In the event of a modification failure, all modifications to the LSP In the event of a modification failure, all modifications to the LSP
including the holding priority must be restored to their original including the holding priority must be restored to their original
values. values.
5. Application of LSP Bandwidth Modification in Dynamic Resource 4. Application of LSP Bandwidth Modification in Dynamic Resource
Management Management
In this section, we gave an example of dynamic network resource In this section, we gave an example of dynamic network resource
management using the LSP bandwidth modification capability. The management using the LSP bandwidth modification capability. The
details of this example can be found in a previous Internet draft details of this example can be found in a previous internet-draft
[2]. Assume that customers or services are assigned with given [2]. Assume that customers or services are assigned with given CR-
CR-LSPs. These customers/services are assigned with one of three LSPs. These customers/services are assigned with one of three
priorities: key, normal or best effort. The network operator does priorities: key, normal or best effort. The network operator does
not want to bump any LSPs during an LSP setup, so after these not want to bump any LSPs during an LSP setup, so after these CR-LSPs
CR-LSPs are set up, their holding priorities are all assigned as are set up, their holding priorities are all assigned as the highest
the highest value. value.
The network operator wants to control the resource on the links of The network operator wants to control the resource on the links of
the LSRs, so each LSR keeps the usage status of its links. Based the LSRs, so each LSR keeps the usage status of its links. Based on
on the usage history, each link is assigned a current threshold the usage history, each link is assigned a current threshold priority
priority Pi, which means that the link has no bandwidth available Pi, which means that the link has no bandwidth available for a Label
for a Label Request with a setup priority lower than Pi. When an Request with a setup priority lower than Pi. When an LSP's bandwidth
LSP's bandwidth needs to be modified, the operator uses a needs to be modified, the operator uses a policy-based algorithm to
policy-based algorithm to assign a priority for its modification assign a priority for its modification request, say Mp for LSP L2.
request, say Mp for LSP L2. The ingress LSR then sends a Label The ingress LSR then sends a Label Request message with Setup
Request message with Setup Priority = Mp. If there is sufficient Priority = Mp. If there is sufficient bandwidth on the link for the
bandwidth on the link for the modification, and the Setup priority modification, and the Setup priority in the Label Request Message is
in the Label Request Message is higher in priority (Mp numerically higher in priority (Mp numerically smaller) than the Pi threshold of
smaller) than the Pi threshold of the link, the Label Request the link, the Label Request Message will be accepted by the LSR.
Message will be accepted by the LSR. Otherwise, the Label Request Otherwise, the Label Request message will be rejected with a
message will be rejected with a Notification message which Notification message which indicates that there are insufficient
indicates that there are insufficient resources. It should also be resources. It should also be noted that when OSPF (or IS-IS) floods
noted that when OSPF (or IS-IS) floods the available-link-bandwidth the available-link-bandwidth information, the available bandwidth
information, the available bandwidth associated with a priority associated with a priority lower than Pi (numerical value bigger)
lower than Pi (numerical value bigger) should be interpreted as _0_. should be interpreted as _0_.
This example based on a priority threshold Pi is implementation This example based on a priority threshold Pi is implementation
specific, and illustrates the flexibility of the modification specific, and illustrates the flexibility of the modification
procedure to prioritize and control network resources. procedure to prioritize and control network resources. The
The calculation of Mp can be network and service dependent, and is calculation of Mp can be network and service dependent, and is based
based on the operator's routing policy. For example, the operator on the operator's routing policy. For example, the operator may
may assign a higher priority (lower Mp value) to L2 bandwidth assign a higher priority (lower Mp value) to L2 bandwidth
modification if L2 belongs to a customer or service with _Key_ modification if L2 belongs to a customer or service with _Key_
priority. The operator may also collect the actual usage of each priority. The operator may also collect the actual usage of each LSP
LSP and assign a lower priority (higher Mp) to L2 and assign a lower priority (higher Mp) to L2 bandwidth-increase
bandwidth-increase modification if, for example, in the past week modification if, for example, in the past week L2 has exceeded its
L2 has exceeded its reserved bandwidth by 2 times on the average. reserved bandwidth by 2 times on the average. In addition, an
In addition, an operator may try to increase the bandwidth of L2 operator may try to increase the bandwidth of L2 on its existing path
on its existing path unsuccessfully if there is insufficient unsuccessfully if there is insufficient bandwidth available on L2.
bandwidth available on L2. In that case, the operator is willing In that case, the operator is willing to increase the bandwidth of
to increase the bandwidth of another LSP, L3, with the same another LSP, L3, with the same ingress/egress LSRs as L2, in order to
ingress/egress LSRs as L2, in order to increase the overall increase the overall ingress/egress bandwidth allocation. However,
ingress/egress bandwidth allocation. However, in this case the in this case the L3 bandwidth modification is performed with a lower
L3 bandwidth modification is performed with a lower priority priority (higher Mp value) since L3 is routed on a secondary path,
(higher Mp value) since L3 is routed on a secondary path, which which results in the higher bandwidth allocation priority being given
results in the higher bandwidth allocation priority being given
to the LSPs that are on their primary paths [2]. to the LSPs that are on their primary paths [2].
6. Acknowledgments 5. Acknowledgments
The authors would like to acknowledge the careful review and The authors would like to acknowledge the careful review and comments
comments of Adrian Farrel. of Adrian Farrel.
7. Intellectual Property Considerations 6. Intellectual Property Considerations
The IETF has been notified of intellectual property rights claimed The IETF has been notified of intellectual property rights claimed in
in regard to some or all of the specification contained in this regard to some or all of the specification contained in this
document. For more information consult the online list of claimed document. For more information consult the online list of claimed
rights. rights.
8. Security Considerations 7. Security Considerations
Protection against modification to LSPs by malign agents has to be Protection against modification to LSPs by malign agents has to be
controlled by the MPLS domain. controlled by the MPLS domain.
9. References 8. References
1 Bradner, S., "The Internet Standards Process -- Revision 3," BCP [1] Bradner, S., "The Internet Standards Process -- Revision 3", BCP
9, RFC 2026, October 1996. 9, RFC 2026, October 1996.
2 Ash, J., et. al., 'Traffic Engineering & QoS Methods for IP-, ATM-, [2] Ash, J., "Traffic Engineering & QoS Methods for IP-, ATM-, &
& TDM-Based Multiservice Networks," draft-oetf-tewg-qos-routing- TDM-Based Multiservice Networks", Work in Progress.
01.txt, work in progress.
3 Jamoussi, B., et. al., "Constraint-Based LSP Setup using LDP, [3] Jamoussi, B., Editor, Andersson, L., Callon, R., Dantu, R., Wu,
draft-ietf-mpls-cr-ldp-04.txt," July 2000, work in progress. L., Doolan, P., Worster, T., Feldman, N., Fredette, A., Girish,
M., Gray, E., Heinanen, J., Kilty, T. and A. Malis, "Constraint-
based LSP Setup Using LDP", RFC 3212, January 2002.
4 Bradner, S., "Key words for use in RFCs to Indicate Requirement [4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels," BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
5 Andersson, L., et. al., "LDP Specification," RFC 3036, January 2001. [5] Andersson, L., Doolan, P., Feldman, N., Fredette, A. and B.
Thomas, "LDP Specification", RFC 3036, January 2001.
6 Rosen et. al., "Multiprotocol Label Switching Architecture," [6] Rosen, E., Viswanathan, A. and R. Callon, "Multiprotocol Label
RFC 3031, January 2001. Switching Architecture", RFC 3031, January 2001.
7 Awduche et. al., "Requirements for Traffic Engineering Over [7] Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M. and J. McManus,
MPLS," RFC 2702, September 1999. "Requirements for Traffic Engineering Over MPLS", RFC 2702,
September 1999.
B Jamoussi, et. al., "Applicability Statement for CR-LDP," [8] Ash, J., Girish, M., Gray, E., Jamoussi,B. and G. Wright,
draft-ietf-mpls-crldp-applic-01,txt, July 2000. "Applicability Statement for CR-LDP", RFC 3213, January 2002.
10. Authors' Addresses 9. Authors' Addresses
Gerald R. Ash Young Lee Gerald R. Ash
AT&T Iris Labs AT&T
Room MT D5-2A01 Phone: 972-943-2964 Room MT D5-2A01
200 Laurel Avenue Email: ylee@irislabs.com 200 Laurel Avenue
Middletown, NJ 07748 Middletown, NJ 07748
USA USA
Phone: 732-420-4578 Phone: 732-420-4578
Email: gash@att.com EMail: gash@att.com
Bilel Jamoussi Bilel Jamoussi
Nortel Networks Corp. Nortel Networks Corp.
600 Tech Park 600 Tech Park
Billerica, MA 01821 Billerica, MA 01821
USA USA
phone: 978-288-4506 Phone: 978-288-4506
Email: jamoussi@NortelNetworks.com EMail: jamoussi@NortelNetworks.com
Peter Ashwood-Smith Li Li Peter Ashwood-Smith
Nortel Networks Corp. SS8 Networks Nortel Networks Corp.
P O Box 3511 Station C 135 Michael Cowpland Drive P O Box 3511 Station C
Ottawa, ON K1Y 4H7 Suite 200 Ottawa, ON K1Y 4H7
Canada Kanata, Ontario Canada
phone: +1 613 763-4534 K2M 2E9 Canada Phone: +1 613 763-4534
Email: petera@NortelNetworks.com phone: +1 613 592-4686 EMail: petera@NortelNetworks.com
Email: lili@ss8networks.com Darek Skalecki
Nortel Networks Corp.
P O Box 3511 Station C
Ottawa, ON K1Y 4H7
Canada
Phone: +1 613 765-2252
EMail: dareks@nortelnetworks.com
Darek Skalecki Don Fedyk Young Lee
Nortel Networks Corp. Nortel Networks Corp. Ceterus Networks
P O Box 3511 Station C 600 Tech Park EMail: ylee@ceterusnetworks.com
Ottawa, ON K1Y 4H7 Billerica, MA 01821
Canada USA
phone: +1 613 765-2252 phone: 978-288-3041
Email: skalecki@NortelNetworks.com fedyk@NortelNetworks.com
Full Copyright Statement Li Li
SS8 Networks
495 March Rd., 5th Floor
Kanata, Ontario
K2K 3G1 Canada
Phone: +1 613 592-2100 ext. 3228
EMail: lili@ss8networks.com
Copyright (C) The Internet Society (date). All Rights Reserved. This Don Fedyk
document and translations of it may be copied and furnished to Nortel Networks Corp.
600 Tech Park
Billerica, MA 01821
USA
Phone: 978-288-3041
EMail: dwfedyk@nortelnetworks.com
10. Full Copyright Statement
Copyright (C) The Internet Society (2002). All Rights Reserved.
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and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
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Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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