Network Working Group
Internet Draft K. Kumaki, Ed.
Intended Status: Informational KDDI Corporation
Created: December 28, 2009 R. Zhang
Expires: June 27, 2010 BT
Y. Kamite
NTT Communications
Requirements for supporting Customer RSVP and RSVP-TE over a
BGP/MPLS IP-VPN
draft-ietf-l3vpn-e2e-rsvp-te-reqts-05.txt
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Abstract
Today, customers expect to run triple play services through
BGP/MPLS IP-VPNs. Some Service Providers will deploy services that
request QoS guarantees from a local CE to a remote CE across the
network. As a result, the application (e.g., voice, video,
bandwidth-guaranteed data pipe, etc.) requirements for an end-to-
end QOS and reserving an adequate bandwidth continue to increase.
Service Providers can use both an MPLS and an MPLS-TE LSP to meet
the service objectives. This document describes service provider
requirements for supporting a customer RSVP and RSVP-TE over a
BGP/MPLS IP-VPN.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in [RFC2119].
Table of Contents
1. Introduction..................................................3
2. Terminology...................................................4
3. Problem Statement.............................................5
4. Application Scenarios.........................................7
4.1 Scenario I: Fast Recovery over BGP/MPLS IP-VPNs...........7
4.2 Scenario II: Strict C-TE LSP QoS Guarantees...............8
4.3 Scenario III: Load Balance of CE-to-CE Traffic............9
4.4 Scenario IV: RSVP Aggregation over MPLS TE Tunnels.......10
4.5 Scenario V: RSVP over Non-TE LSPs........................11
4.6 Scenario VI: RSVP-TE over Non-TE LSPs....................12
5. Detailed Requirements for C-TE LSPs Model....................12
5.1 Selective P-TE LSPs.....................................12
5.2 Graceful Restart Support for C-TE LSPs..................13
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5.3 Rerouting Support for C-TE LSPs.........................13
5.4 FRR Support for C-TE LSPs...............................13
5.5 Admission Control Support on P-TE LSP Head-Ends.........13
5.6 Admission Control Support for C-TE LSPs in LDP-based Core
Networks.....................................................14
5.7 Policy Control Support for C-TE LSPs....................14
5.8 PCE Features Support for C-TE LSPs......................14
5.9 Diversely Routed C-TE LSPs Support......................15
5.10 Optimal Path Support for C-TE LSPs......................15
5.11 Reoptimization Support for C-TE LSPs....................15
5.12 DS-TE Support for C-TE LSPs.............................15
6. Detailed Requirements for C-RSVP Paths Model.................16
6.1 Admission Control between PE-CE for C-RSVP Paths........16
6.2 Aggregation of C-RSVP Paths by P-TE LSPs................16
6.3 Non-TE LSPs support for C-RSVP Paths....................16
6.4 Transparency of C-RSVP Paths............................16
7. Common Detailed Requirements for Two Models..................16
7.1 CE-PE Routing...........................................17
7.2 Complexity and Risks....................................17
7.3 Backward Compatibility..................................17
7.4 Scalability Considerations..............................17
7.5 Performance Considerations..............................17
7.6 Management Considerations...............................18
8. Security Considerations......................................18
9. IANA Considerations..........................................19
10. References..................................................19
10.1 Normative References....................................19
10.2 Informative References..................................20
11. Acknowledgments.............................................21
12. Author's Addresses..........................................21
Appendix A. Reference Model.....................................21
A.1 End-to-End C-RSVP Path Model.............................22
A.2 End-to-End C-TE LSP Model................................22
1. Introduction
Some Service Providers want to build a service which guarantees
QoS and a bandwidth from a local CE to a remote CE through the
network. A CE includes the network client equipment owned and
operated by the service provider. However, the CE may not be part
of the MPLS provider network.
Today, customers expect to run triple play services such as the
internet access, the telephone and the television through BGP/MPLS
IP-VPNs [RFC4364].
As these services evolve, the requirements for an end-to-end QoS
to meet the application requirements also continue to grow.
Depending on the application (e.g., voice, video, bandwidth-
guaranteed data pipe, etc.), a native IP using an RSVP and/or an
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end-to-end constrained MPLS-TE Label Switched Path (LSP) may be
required. The RSVP path may be used to provide QoS guarantees and
reserve an adequate bandwidth for the data. An end-to-end MPLS-TE
LSP may also be used to guarantee a bandwidth, and provide
extended functionality like MPLS fast reroute (FRR)[RFC4090] for
maintaining the service continuity around node and link,
including the CE-PE link, failures. It should be noted that an
RSVP session between two CEs may also be mapped and tunneled into
an MPLS-TE LSP across an MPLS provider network.
A number of advantages exist for deploying the model previously
mentioned. The first is that customers can use these network
services whilst being able to use both private addresses and
global addresses. The second advantage is that the traffic is
tunneled through the Service Provider backbone, so that the
customer traffic and the route confidentiality are maintained.
This document defines a reference model, example application
scenarios and detailed requirements for a solution supporting
a customer RSVP and RSVP-TE over a BGP/MPLS IP-VPN.
Specification for a solution is out of scope in this document.
2. Terminology
This document uses the BGP/MPLS IP-VPN terminology defined in
[RFC4364]. The document also uses Path Computation Element terms
which are defined in [RFC4655].
TE LSP: Traffic Engineering Label Switched Path
MPLS TE LSP: Multi Protocol Label Switching TE LSP
C-RSVP path: Customer RSVP path: a native RSVP path with the
bandwidth reservation of X for customers
C-TE LSP: Customer Traffic Engineering Label Switched Path:
an end-to-end MPLS TE LSP for customers
P-TE LSP: Provider Traffic Engineering Label Switched Path: a
transport TE LSP between two PEs
Head-end LSR: an ingress LSR
Tail-end LSR: an egress LSR
LSR: a Label Switched Router
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3. Problem Statement
Service Providers want to deliver triple play services with QOS
guarantees to their customers. Various techniques are available to
achieve this. Some Service Providers will wish to offer advanced
services using an RSVP signaling for native IP flows (C-RSVP) or
an RSVP-TE signaling for Customer TE LSPs (C-TE LSPs) over
BGP/MPLS IP-VPNs.
The following examples outline each method:
A C-RSVP path with the bandwidth reservation of X can be used to
transport the voice. In order to achieve the sub-50msec recovery
during link, node and SRLG failures and to provide strict QoS
guarantees, a C-TE LSP with the bandwidth X between data centers
or customer sites can be used to carry the voice and the video
traffic. Thus, service providers or customers can choose a C-RSVP
path or a C-TE LSP to meet their requirements.
When service providers offer a C-RSVP path between hosts or CEs
over BGP/MPLS IP-VPNs, the CE/host requests an end-to-end C-RSVP
path with the bandwidth reservation of X to the remote CE/host.
However, if a C-RSVP signaling is to send within a VPN, the
service provider network will face scalability issues because
routers need to retain the RSVP state per a customer. Therefore,
in order to solve scalability issues, multiple C-RSVP
reservations can be aggregated at a PE, where a P-TE LSP
head-end can perform the admission control using the aggregated
C-RSVP reservations. The method that is described in RFC4804 can
be considered as a useful approach. In this case, a reservation
request from within the context of a VRF can get aggregated onto
a P-TE LSP. The P-TE LSP can be pre-established, resized based on
the request, or triggered by the request. Service providers,
however, cannot provide a C-RSVP path over the VRF instance as
defined in RFC4364. The current BGP/MPLS IP-VPN architecture also
does not support an RSVP instance running in the context of a VRF
to process RSVP messages and integrated services (int-serv)
[RFC1633][RFC2210]. One of solutions is described in [RSVP-L3VPN].
If service providers offer a C-TE LSP from a CE to a CE over the
BGP/MPLS IP-VPN, they require that a MPLS TE LSP from a local CE
to a remote CE be established. However, if a C-TE LSP signaling
is to send within the VPN, the service provider network may face
the following scalability issues:
- A C-TE LSP can be aggregated by a P-TE LSP at a PE. (i.e.
hierarchical LSPs) In this case, only a PE maintains the state
about customer RSVP sessions.
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- A C-TE LSP cannot be aggregated by a P-TE LSP at a PE depending
on some policies. (i.e. continuous LSPs)
In this case, both Ps and PEs maintain the state about customer
RSVP sessions.
- A C-TE LSP can be aggregated by the non-TE LSP (i.e. LDP).
In this case, only a PE maintains the state about customer
RSVP-TE sessions.
Note that it is assumed there is always enough bandwidth
available in the service provider core network.
Furthermore, if service providers provide the C-TE LSP over the
BGP/MPLS IP-VPN, they currently cannot provide it over the VRF
Instance as defined in RFC4364. Specifically the current BGP/MPLS
IP-VPN architecture does not support the RSVP-TE instance running
in the context of a VRF to process RSVP messages and trigger the
establishment of the C-TE LSP over the service provider core
network. If every C-TE LSP is to trigger the establishment or
resizing of a P-TE LSP, the service provider network will also
face scalability issues that arise from maintaining a large number
of the P-TE LSP and/or the dynamic signaling of these P-TE LSPs.
Section 8.4, Scalability Considerations, of this document provides
the detailed scalability requirements.
Two different models are described above. The differences between
C-RSVP paths and C-TE LSPs are as follows:
- C-RSVP path model: data packets among CEs are forwarded by
"native IP packets" (i.e. not labeled packets).
- C-TE LSP model: data packets among CEs are forwarded by
"labeled IP packets".
Depending on the service level and the need to meet specific
requirements, service providers should be able to choose P-TE LSPs
or non-TE LSPs in the backbone network. The selection may be
dependent on the Service Providers policy and the node capability
to support the mechanisms described.
The following items are required selectively to support C-RSVP
paths and C-TE LSPs over BGP/MPLS IP-VPNs based on the service
level. For example, some service providers need all of the
following items to provide a service. Some service providers need
some of them to provide the service. It depends on a service level
and a policy of service providers. Detailed requirements are
described in sections 6, 7 and 8.
- C-RSVP path QoS guarantees.
- Fast recovery over the BGP/MPLS IP-VPN to protect traffic for
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the C-TE LSP against the CE-PE link failure and the PE node
failure.
- Strict C-TE LSP bandwidth and QoS guarantees.
- Resource optimization for C-RSVP paths and C-TE LSPs.
- Scalability for C-RSVP paths and C-TE LSPs.
4. Application Scenarios
The following sections present a few application scenarios for
C-RSVP paths and C-TE LSPs in BGP/MPLS IP-VPN environments.
Appendix A. (Reference Model), describes a C-RSVP path, a C-TE LSP
and a P-TE LSP.
In all scenarios, it is the responsibility of the service provider
to ensure that the enough bandwidth is available to meet the
customers application requirements.
4.1 Scenario I: Fast Recovery over BGP/MPLS IP-VPNs
In this scenario, as shown in figure 1, a customer uses a VoIP
application between its sites (i.e., between CE1 and CE2).
H0 and H1 are voice equipments.
In this case, the customer establishes C-TE LSP1 as a primary
Path and C-TE LSP2 as a backup path. If the link between PE1
and CE1 or the node of PE1 fails, C-TE LSP1 needs C-TE LSP2 as a
path protection.
Generally speaking, C-RSVP paths are used by customers and P-TE
LSPs are used by service providers.
C-TE LSP1
<---------------------------------------------->
P-TE LSP1
<--------------------------->
............. .............
. --- --- . --- --- --- --- . --- --- .
.|H0 | |CE1|-----|PE1|----|P1 |-----|P2 |----|PE2|-----|CE2| |H1 |.
. --- --- . --- --- --- --- . --- --- .
.........|... --- --- --- --- ...|.........
+-------|PE3|----|P3 |-----|P4 |----|PE4|-------+
--- --- --- ---
<--------------------------->
P-TE LSP2
<---------------------------------------------->
C-TE LSP2
<--customer--> <--------BGP/MPLS IP-VPN-------> <--customer->
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network network
Figure 1 Scenario I
4.2 Scenario II: Strict C-TE LSP QoS Guarantees
In this scenario, as shown in figure 2, a service provider B
transports the voice and the video traffic between its sites (i.e.,
between CE1 and CE2).
In this case, the service provider B establishes C-TE LSP1 with
the preemption priority 0 and the bandwidth 100Mbps for the voice
traffic, and C-TE LSP2 with the preemption priority 1 and the
bandwidth 200Mbps for the unicast video traffic. On the other hand,
a service provider A also pre-establishes P-TE LSP1 with the
preemption priority 0 and the bandwidth 1Gbps for the voice
traffic, and P-TE LSP2 with the preemption priority 1 and the
bandwidth 2Gbps for the video traffic. These P-TE LSP1 and P-TE
LSP2 should support DS-TE. [RFC4124]
PE1 and PE3 should choose an appropriate P-TE LSP based on the
preemption priority. In this case, C-TE LSP1 must be associated
with P-TE LSP1 at PE1 and C-TE LSP2 must be associated with P-TE
LSP2 at PE3.
Furthermore, PE1 and PE3 head-ends should control the bandwidth of
C-TE LSPs. In this case, PE1 and PE3 can choose C-TE LSPs by the
amount of max available bandwidth for each P-TE LSP, respectively.
C-TE LSP1
<---------------------------------------------->
P-TE LSP1
<--------------------------->
............. .............
. --- --- . --- --- --- --- . --- --- .
.|CE0| |CE1|-----|PE1|----|P1 |-----|P2 |----|PE2|-----|CE2| |CE3|.
. --- --- . --- --- --- --- . --- --- .
.........|... --- --- --- --- ...|.........
+-------|PE3|----|P3 |-----|P4 |----|PE4|-------+
--- --- --- ---
<--------------------------->
P-TE LSP2
<---------------------------------------------->
C-TE LSP2
<---SP B----> <--------BGP/MPLS IP-VPN-------> <---SP B--->
network SP A network network
Figure 2 Scenario II
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It's possible that the customer and the service provider have
differing preemption priorities. In this case, the PE policy will
override the customers. In the case that the service provider does
not support preemption priorities then priorities should be
ignored.
4.3 Scenario III: Load Balance of CE-to-CE Traffic
In this scenario, as shown in figure 3, the service provider C
uses the voice and the video traffic between its sites (i.e.,
between CE0 and CE5/CE7, between CE2 and CE5/CE7, between CE5 and
CE0/CE2, and between CE7 and CE0/CE2). H0 and H1 are voice and
video equipments. In this case, the service provider C establishes
C-TE LSP1, C-TE LSP3, C-TE LSP5 and C-TE LSP7 with the preemption
priority 0 and the bandwidth 100Mbps for the voice traffic, and
establishes C-TE LSP2, C-TE LSP4, C-TE LSP6 and C-TE LSP8 with the
preemption priority 1 and the bandwidth 200Mbps for the video
traffic. On the other hand, the service provider A also pre-
establishes P-TE LSP1 and P-TE LSP3 with the preemption priority 0
and the bandwidth 1Gbps for the voice traffic, and P-TE LSP2 and
P-TE LSP4 with the preemption priority 1 and the bandwidth 2Gbps
for the video traffic. These P-TE LSP1, P-TE LSP2, P-TE LSP3 and
P-TE LSP4 should support DS-TE.[RFC4124]
All PEs should choose an appropriate P-TE LSP based on the
preemption priority. To minimize the traffic disruption due to a
single network failure, diversely routed C-TE LSPs are
established. In this case, the FRR [RFC4090] is not necessarily
required.
Also, unconstrained TE LSPs (i.e., C-TE LSPs/P-TE LSPs with the 0
bandwidth) [RFC5330] are applicable to this scenario.
Furthermore, the load balancing for a communication between H0
and H1 can be done by setting up full mesh C-TE LSPs between
CE0/CE2 and CE5/CE7.
C-TE LSP1(P=0),2(P=1) (CE0->CE1->...->CE4->CE5)
(CE0<-CE1<-...<-CE4<-CE5)
<---------------------------------------------->
C-TE LSP3(P=0),4(P=1) (CE2->CE1->...->CE4->CE7)
(CE2<-CE1<-...<-CE4<-CE7)
<---------------------------------------------->
P-TE LSP1 (p=0)
<-------------------->
P-TE LSP2 (p=1)
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<-------------------->
.................. ..................
. --- --- . --- --- --- --- . --- --- .
. |CE0|-|CE1|--|PE1|--|P1 |---|P2 |--|PE2|--|CE4|-|CE5| .
. --- /--- --- . --- --- --- --- . --- ---\ --- .
.|H0 | + . + . + |H1 |.
. --- \--- --- . --- --- --- --- . --- ---/ --- .
. |CE2|-|CE3|--|PE3|--|P3 |---|P4 |--|PE4|--|CE6|-|CE7| .
. --- --- . --- --- --- --- . --- --- .
.................. ..................
<-------------------->
P-TE LSP3 (p=0)
<-------------------->
P-TE LSP4 (p=1)
<---------------------------------------------->
C-TE LSP5(P=0),6(P=1) (CE0->CE3->...->CE6->CE5)
(CE0<-CE3<-...<-CE6<-CE5)
<---------------------------------------------->
C-TE LSP7(P=0),8(P=1) (CE2->CE3->...->CE6->CE7)
(CE2<-CE3<-...<-CE6<-CE7)
<-----SP C-----> <----BGP/MPLS IP-VPN----> <-----SP C----->
network SP A network network
Figure 3 Scenario III
4.4 Scenario IV: RSVP Aggregation over MPLS TE Tunnels
In this scenario, as shown in figure 4, the customer has two hosts
connecting off CE1 and CE2 respectively. CE1 and CE2 are connected
to PE1 and PE2, respectively, within a VRF instance belonging to
the same VPN. The requesting host (H1) may request to the H2 an
RSVP path with the bandwidth reservation of X. This reservation
request from within the context of VRF will get aggregated onto a
pre-established P-TE/DS-TE LSP based upon procedures similar to
[RFC4804]. As in the case of [RFC4804], there may be multiple P-TE
LSPs belonging to different DS-TE class-types. Local policies can
be implemented to map the incoming RSVP path request from H1 to
the P-TE LSP with the appropriate class-type. Please note that the
e2e RSVP path request may also be initiated by the CE devices
themselves.
C-RSVP path
<----------------------------------------------------->
P-TE LSP
<--------------------------->
............. .............
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. --- --- . --- --- --- --- . --- --- .
.|H1 | |CE1|---|PE1|----|P1 |-----|P2 |----|PE2|---|CE2| |H2 |.
. --- --- . --- --- --- --- . --- --- .
............. .............
^ ^
| |
vrf instance vrf instance
<-customer-> <--------BGP/MPLS IP-VPN-------> <-customer->
network network
Figure 4 Scenario IV
4.5 Scenario V: RSVP over Non-TE LSPs
In this scenario, as shown in figure 5, a customer has two hosts
connecting off CE1 and CE2, respectively. CE1 and CE2 are
connected to PE1 and PE2, respectively, within a VRF instance
belonging to the same VPN. The requesting host (H1) may request
to H2 an RSVP path with the bandwidth reservation of X. In this
case, a non-TE LSP (i.e. LDP etc) is provided between PEs and has
LDP which supports MPLS diffserv [RFC3270].
Note that this only provides Diffserv and not the bandwidth
reservation as is done with RSVP-TE.
Local policies can be implemented to map the customer's reserved
flow to the LSP with the appropriate Traffic Class [RFC5462] at
PE1.
C-RSVP path
<------------------------------------------>
Non-TE LSP
<--------------------------->
............. .............
. --- --- . --- --- --- --- . --- --- .
.|H1 | |CE1|---|PE1|----|P1 |-----|P2 |----|PE2|---|CE2| |H2 |.
. --- --- . --- --- --- --- . --- --- .
............. .............
^ ^
| |
vrf instance vrf instance
<-customer-> <-------BGP/MPLS IP-VPN-------> <-customer->
network network
Figure 5 Scenario V
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4.6 Scenario VI: RSVP-TE over Non-TE LSPs
In this scenario, as shown in figure 6, a customer uses a VoIP
application between its sites (i.e., between CE1 and CE2). H0
and H1 are voice equipments. In this case, a non-TE LSP means
LDP and the customer establishes C-TE LSP1 as a primary path and
C-TE LSP2 as a backup path. If the link between PE1 and CE1 or
the node of PE1 fails, C-TE LSP1 needs C-TE LSP2 as a path
protection.
C-TE LSP1
<----------------------------------------->
Non-TE LSP
<-------------------------->
............. .............
. --- --- . --- --- --- --- . --- --- .
.|H0 | |CE1|---|PE1|----|P1 |-----|P2 |----|PE2|---|CE2| |H1 |.
. --- --- . --- --- --- --- . --- --- .
.........|... --- --- --- --- ...|.........
+-----|PE3|----|P3 |-----|P4 |----|PE4|-----+
--- --- --- ---
<-------------------------->
Non-TE LSP
<----------------------------------------->
C-TE LSP2
<-customer-> <------BGP/MPLS IP-VPN------> <-customer->
network network
Figure 6 Scenario VI
5. Detailed Requirements for C-TE LSPs Model
This section describes detailed requirements for C-TE LSPs in
BGP/MPLS IP-VPN environments.
5.1 Selective P-TE LSPs
The solution MUST provide the ability to decide which P-TE LSPs a
PE uses for a C-RSVP path and a C-TE LSP. When a PE receives a
native RSVP and/or a path messages from a CE, it MUST be able to
decide which P-TE LSPs it uses. In this case, various kinds of
P-TE LSPs exist in the service provider network. For example, the
PE MUST choose an appropriate P-TE LSP based on local policies
such as:
1. preemption priority
2. affinity
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3. class-type
4. on the data plane: (DSCP or Traffic Class bits)
5.2 Graceful Restart Support for C-TE LSPs
The solution SHOULD support the graceful restart capability,
where the C-TE LSP traffic continues to be forwarded during a PE
graceful restart, graceful restart mechanisms related to this
architecture are described in [RFC3473], [RFC3623] and [RFC4781].
5.3 Rerouting Support for C-TE LSPs
The solution MUST provide the rerouting of a C-TE LSP in case of
Link, node and SRLG failures or preemption. Such rerouting may be
controlled by a CE or by a PE depending on the failure. In a dual
homed environment, the ability to perform the rerouting MUST be
provided against a CE-PE link failure or a PE failure if another
is available between the head-end and the tail-end of the C-TE
LSP.
5.4 FRR Support for C-TE LSPs
The solution MUST support FRR [RFC4090] features for a C-TE LSP
over a vrf instance.
In BGP/MPLS IP-VPN environments, a C-TE LSP from a CE traverses
multiple PEs and Ps, albeit tunneled over a P-TE LSP. In order to
avoid PE-CE link/PE node/SRLG failures, a CE (a customer's head-end
router) needs to support the link protection or the node
protection.
The following protection MUST be supported:
1. CE link protection
2. PE node protection
3. CE node protection
5.5 Admission Control Support on P-TE LSP Head-Ends
The solution MUST support the admission control on a P-TE LSP
tunnel head-end for C-TE LSPs. C-TE LSPs may potentially try to
reserve the bandwidth that exceeds the bandwidth of the P-TE LSP.
The P-TE LSP tunnel head-end SHOULD control the number of
C-TE LSPs and/or the bandwidth of C-TE LSPs. For example, the
transport TE LSP head-end SHOULD have a configurable limit on
the maximum number of C-TE LSPs that it can admit from a CE. As
for the amount of bandwidth that can be reserved by C-TE LSPs
there could be two situations:
1. Let the P-TE LSP do its natural bandwidth admission
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2. Set a cap on the amount of bandwidth and have the configuration
option to:
a. Reserve the minimum of the cap bandwidth or the C-TE LSP
bandwidth on the P-TE LSP if the required bandwidth is available
b. Reject the C-TE LSP if the required bandwidth by the C-TE LSP
is not available
5.6 Admission Control Support for C-TE LSPs in LDP-based Core
Networks
The solution MUST support the admission control for a C-TE LSP at
a PE in the LDP-based core network. Specifically, PEs MUST have a
configurable limit on the maximum amount of bandwidth that can be
reserved by C-TE LSPs per a vrf instance (i.e. per a customer).
Also, a PE SHOULD have a configurable limit on the total amount of
bandwidth that can be reserved by C-TE LSPs between PEs.
5.7 Policy Control Support for C-TE LSPs
The solution MUST support the policy control for a C-TE LSP at a
PE.
The PE MUST be able to perform the following:
1. Limit the rate of RSVP messages per CE link.
2. Accept and map or reject requests for a given affinity.
3. Accept and map or reject requests with a specified setup and/or
pre-emption priorities.
4. Accept or reject requests for fast reroutes.
5. Neglect the requested setup and/or pre-emption priorities and
select a P-TE LSP based on a local policy that applies to the CE-PE
link or the VRF.
6. Ignore the requested affinity and select a P-TE LSP based on a
local policy that applies to the CE-PE link or the VRF.
7. Perform mapping in data plane between customer traffic class
bits and transport P-TE LSP traffic class bits, as signaled per
[RFC3270].
5.8 PCE Features Support for C-TE LSPs
The solution SHOULD support the PCE architecture for a C-TE LSP
establishment in the context of a VRF instance. When a C-TE LSP is
provided, CEs, PEs and Ps may support PCE [RFC4655] and [RFC5440]
features.
In this case, CE routers or PE routers may be PCCs and PE routers
and/or P routers may be PCEs. Furthermore, the solution SHOULD
support a mechanism for the dynamic PCE discovery. Specifically,
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all PCEs are not necessarily discovered automatically and only
specific PCEs that know VPN routes should be discovered
automatically.
5.9 Diversely Routed C-TE LSPs Support
The solution MUST provide for setting up diversely routed C-TE
LSPs over the VRF instance. These diverse C-TE LSPs MAY be
traversing over two different P-TE LSPs that are fully disjoint
within a service provider network. When a single CE has multiple
uplinks which connect to different PEs, it is desirable that
multiple C-TE LSPs over the VRF instance are established between
a pair of LSRs. When two CEs have multiple uplinks which connect
to different PEs, it is desirable that multiple C-TE LSPs over the
VRF instance are established between two different pairs of LSRs.
In these cases, for example, the following points will be
beneficial to customers.
1. load balance of the CE-to-CE traffic across diverse C-TE LSPs
so as to minimize the traffic disruption in case of a single
network element failure
2. path protection (e.g. 1:1, 1:N)
5.10 Optimal Path Support for C-TE LSPs
The solution MUST support the optimal path for a C-TE LSP over the
VRF instance. Depending on an application (e.g. voice and video),
an optimal path is needed for a C-TE LSP over the vrf instance. An
optimal path may be a shortest path based on the TE metric, in the
case of a TE-LSP or an IGP metric, in the case of LDP.
5.11 Reoptimization Support for C-TE LSPs
The solution MUST support the reoptimization of a C-TE LSP over
the VRF instance. These LSPs MUST be reoptimized using
make-before-break[RFC3209].
In this case, it is desirable for a CE to be configured with
regard to the timer-based or event-driven reoptimization.
Furthermore, customers SHOULD be able to reoptimize a C-TE LSP
manually. To provide the delay-sensitive or jitter-sensitive
traffic (i.e. the voice traffic), a C-TE LSP path computation
and a route selection are expected to optimal for the specific
application.
5.12 DS-TE Support for C-TE LSPs
The solution MUST support DS-TE [RFC4124] for a C-TE LSP over the
VRF instance. In the event that the service provider and the
customer have differing bandwidth constraint models, then only
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the service provider bandwidth model should be supported.
Applications, which have different traffic characteristics, are
used
in BGP/MPLS IP-VPN environments. Service providers try to achieve
the fine-grained optimization of transmission resources,
efficiency and further enhanced network performance. It may be
desirable to perform TE at a per-class level.
By mapping the traffic from a given diff-serv class of service on
a separate C-TE LSP, it allows this traffic to utilize resources
available to the given class on both shortest paths and
non-shortest paths, and follow paths that meet TE constraints
which are specific to the given class.
6. Detailed Requirements for C-RSVP Paths Model
This section describes detailed requirements for C-RSVP paths in
BGP/MPLS IP-VPN environments.
6.1 Admission Control between PE-CE for C-RSVP Paths
The solution MUST support the admission control at the ingress PE.
PEs MUST control RSVP messages per a vrf.
6.2 Aggregation of C-RSVP Paths by P-TE LSPs
The solution SHOULD support C-RSVP paths aggregated by P-TE LSPs.
P-TE LSPs SHOULD be pre-established manually or dynamically by
operators, and MAY be established triggered by C-RSVP messages.
Also, the P-TE LSP SHOULD support DS-TE.
6.3 Non-TE LSPs support for C-RSVP Paths
The solution SHOULD support non-TE LSPs (i.e. LDP-based LSP,
etc). They are established by LDP [RFC5036] between PEs, and
supports MPLS diffserv [RFC3270]. The solution MAY support local
policies to map the customer's reserved flow to the LSP with the
appropriate Traffic Class at the PE.
6.4 Transparency of C-RSVP Paths
The solution SHOULD NOT change RSVP messages from the local CE to
the remote CE (Path, Resv, Path Error, Resv Error, etc).
The solution SHOULD allow customers to receive RSVP messages
transparently between CE sites.
7. Common Detailed Requirements for Two Models
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This section describes common detailed requirements for C-TE LSPs
and C-RSVP paths in BGP/MPLS IP-VPN environments.
7.1 CE-PE Routing
The solution SHOULD support the following routing configuration on
the CE-PE links with either RSVP or RSVP-TE on the CE-PE link:
1. static routing
2. BGP routing
3. OSPF
4. OSPF-TE (RSVP-TE case only)
7.2 Complexity and Risks
The solution SHOULD avoid introducing unnecessary complexity to
the current operating network to such a degree that it would
affect the stability and diminish the benefits of deploying such a
solution over SP networks.
7.3 Backward Compatibility
The deployment of C-RSVP paths and C-TE LSPs SHOULD avoid
impacting existing RSVP and MPLS TE mechanisms respectively, but
allow for a smooth migration or co-existence.
7.4 Scalability Considerations
The solution SHOULD minimize the impact on network scalability
from a C-RSVP path and a C-TE LSP over the VRF instance.
As indentified in earlier sections, PCE provides a method for
offloading computation of C-TE LSPs and help with the solution
scalability.
The solution MUST address the scalability of C-RSVP paths and
C-TE LSPs for the following protocols.
1. RSVP (e.g. number of RSVP messages, retained state etc).
2. RSVP-TE (e.g. number of RSVP control messages, retained state,
message size etc).
3. BGP (e.g. number of routes, flaps, overloads events etc).
7.5 Performance Considerations
The solution SHOULD be evaluated with regard to the following
criteria.
1. Degree of path optimality of the C-TE LSP.
2. TE LSP setup time.
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3. Failure and restoration time.
4. Impact and scalability of the control plane due to added
overheads.
5. Impact and scalability of the data/forwarding plane due to
added overheads.
7.6 Management Considerations
The solution MUST address the manageability of C-RSVP paths and
C-TE LSPs for the following considerations.
1. Need for a MIB module for control plane (including mapping of
P-TE LSP and C-TE LSPs) and bandwidth monitoring.
2. Need for diagnostic tools (this include Trace Route and PING).
The solution MUST allow routers to support the MIB module for
C-RSVP paths and C-TE LSPs per a vrf instance. If a CE is managed
by service providers, the solution MUST allow service providers
to collect MIB information for C-RSVP paths and C-TE LSPs from
the CE per a customer.
Diagnostic tools can detect failures of the control plane and the
data plane for general MPLS TE LSPs [RFC4379]. The solution MUST
allow routers to be able to detect failures of the control and
the data plane for C-TE LSPs over a VRF instance.
MPLS OAM for C-TE LSPs MUST be supported within the context of VRF
except for the above.
8. Security Considerations
Any solution should consider the following general security
requirements:
1. The solution SHOULD NOT divulge the service provider topology
information to the customer network.
2. The solution SHOULD minimize the service provider network
vulnerability to Denial of Service (DoS) attacks.
3. The solution SHOULD minimize the misconfiguration of DSCP
marking, preemption, and holding priorities of the customer
traffic.
The following additional security issues for C-TE LSPs relate to
both control plane and data plane.
In terms of the control plane, in the models of C-RSVP paths and
C-TE LSPs both, a PE receives IPv4 or IPv6 RSVP control packets
from a CE. If the CE is a router that is not trusted by service
providers, the PE MUST be able to limit the rate and number of
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IPv4 or IPv6 RSVP control packets.
In terms of the data plane, in the model of C-TE LSPs, a PE
receives labeled IPv4 or IPv6 data packets from a CE. If the CE
is a router that is not trusted by service providers, the PE
MUST be able to limit the rate of labeled IPv4 or IPv6 data
packets. If the CE is a trusted router for service providers,
the PE MAY be able to limit the rate of labeled IPv4 or IPv6
data packets. Specifically, the PE must drop MPLS-labeled
packets if the MPLS label was not assigned over the PE-CE link
on which the packet was received. The PE must also be able to
police traffic to the traffic profile associated with the LSP on
which traffic is received on the PE-CE link.
Moreover, flooding RSVP/RSVP-TE control packets from malicious
customers must be avoided. Therefore, a PE MUST isolate the
impact of such customer's RSVP/ RSVP-TE packets from other
customers.
In the event that C-TE LSPs are diversely routed over VRF
instances, the VRF should indicate to the CE how such diversity
was provided.
9. IANA Considerations
This requirement document makes no requests for IANA action.
10. References
10.1 Normative References
[RFC1633] Braden, R., et al., "Integrated Services in the
Internet Architecture: an Overview", RFC 1633, June
1994.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2210] Wroclawski, J., "The Use of RSVP with IETF Integrated
Services", RFC 2210, September 1997.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan,
V. and Swallow, G., "RSVP-TE: Extensions to RSVP for
LSP Tunnels", RFC 3209, December 2001.
[RFC3270] Le Faucheur, F., "Multi-Protocol Label Switching
(MPLS) Support of Differentiated Services", RFC 3270,
May 2002.
K.Kumaki, et al. [Page 19]
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[RFC3473] Berger, L., "Generalized Multi-Protocol Label
Switching(GMPLS) Signaling Resource ReserVation
Protocol-Traffic Engineering (RSVP-TE) Extensions",
RFC 3473, January 2003.
[RFC3623] Moy, J., et al., "Graceful OSPF Restart", RFC3623,
November 2003.
[RFC4090] Pan, P., Swallow, G. and A. Atlas, "Fast Reroute
Extensions to RSVP-TE for LSP Tunnels", RFC 4090, May
2005.
[RFC4124] Le Faucheur, F., "Protocol Extensions for Support of
Diffserv-aware MPLS Traffic Engineering", RFC 4124,
June 2005.
[RFC4364] Rosen, E., and Rekhter, Y., "BGP/MPLS IP Virtual
Private Networks (VPNs)", RFC 4364, February 2006.
[RFC4379] Kompella, K. and G. Swallow, "Detecting MPLS Data
Plane Failures", RFC 4379, February 2006.
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "Path
Computation Element (PCE) Architecture", RFC 4655,
August 2006.
[RFC4781] Rekhter, Y. and Aggarwal, R., "Graceful Restart
Mechanism for BGP with MPLS", RFC 4781, January 2007.
[RFC5036] Andersson, L., Minei, I. and Thomas, B., "LDP
Specification", RFC 5036, October 2007.
[RFC5462] Andersson, L. and Asati, R., "Multiprotocol Label
Switching (MPLS) Label Stack Entry: "EXP" Field
Renamed to "Traffic Class" Field", RFC 5462,
February 2009.
10.2 Informative References
[RSVP-L3VPN] Davie, B., et al., "Support for RSVP in Layer 3 VPNs",
Work in Progress, February 2008.
[RFC4804] Le Faucheur, F., et al., "Aggregation of RSVP
Reservations over MPLS TE/DS-TE Tunnels", RFC4804,
February 2007.
[RFC5330] Vasseur, J.-P., et al., "A Link-Type sub-TLV to convey
the number of Traffic Engineering Label Switched Paths
signaled with zero reserved bandwidth across a link",
K.Kumaki, et al. [Page 20]
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RFC5330, October 2008.
[RFC5440] Vasseur, J.-P., et al., "Path Computation Element(PCE)
communication Protocol (PCEP) - Version 1", RFC5440,
March 2009.
11. Acknowledgments
The author would like to express the thanks to Nabil Bitar, David
McDysan and Daniel King for their helpful and useful comments and
feedback.
12. Author's Addresses
Kenji Kumaki (Editor)
KDDI Corporation
Garden Air Tower
Iidabashi, Chiyoda-ku,
Tokyo 102-8460, JAPAN
Email: ke-kumaki@kddi.com
Raymond Zhang
BT Infonet
2160 E. Grand Ave.
El Segundo, CA 90025
Email: raymond.zhang@bt.infonet.com
Yuji Kamite
NTT Communications Corporation
Tokyo Opera City Tower
3-20-2 Nishi Shinjuku, Shinjuku-ku
Tokyo 163-1421, Japan
Email: y.kamite@ntt.com
Appendix A. Reference Model
In this appendix, a C-RSVP path, a C-TE LSP and a P-TE LSP are
explained.
All scenarios in this appendix assume the following:
- A P-TE LSP is established between PE1 and PE2. This LSP is used
by the VRF instance to forward customer packets within a
BGP/MPLS IP-VPN.
- The Service Provider has ensured that enough bandwidth is
available to meet the service requirements.
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A.1 End-to-End C-RSVP Path Model
A C-RSVP path and a P-TE LSP are shown in figure 1 in the context
of a BGP/MPLS IP-VPN. A P-TE LSP may be a non-TE LSP (i.e. LDP) in
some cases. In the case of a non-TE mechanism, however, it may
be difficult to guarantee an end-to-end bandwidth as resources
are shared.
CE0/CE1 requests an e2e C-RSVP path to CE3/CE2 with the bandwidth
reservation of X. At PE1, this reservation request received in
the context of a VRF will get aggregated onto a pre-established
P-TE LSP, or trigger the establishment of a new P-TE LSP.
It should be noted that C-RSVP sessions across different BGP/MPLS
IP-VPNs can be aggregated onto the same P-TE LSP between the same
PE pair, achieving further scalability. [RFC4804] defines this
scenario in more detail.
The RSVP control messages (e.g. an RSVP PATH message and an RSVP
RESV message) exchanged among CEs are forwarded by IP packets
through the BGP/MPLS IP-VPN. After CE0 and/or CE1 receive
a reservation message from CE2 and/or CE3, CE0/CE1 establishes
a C-RSVP path through the BGP/MPLS IP-VPN.
C-RSVP path
<------------------------------------------>
P-TE LSP
<--------------------------->
............. .............
. --- --- . --- --- --- --- . --- --- .
.|CE0| |CE1|---|PE1|----|P1 |-----|P2 |----|PE2|---|CE2| |CE3|.
. --- --- . --- --- --- --- . --- --- .
............. .............
^ ^
| |
vrf instance vrf instance
<-customer-> <------BGP/MPLS IP-VPN------> <-customer->
network network
or or
another another
service provider service provider
network network
Figure 1 e2e C-RSVP path model
A.2 End-to-End C-TE LSP Model
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A C-TE LSP and a P-TE LSP are shown in figure 2 in the context of
a BGP/MPLS IP-VPN. A P-TE LSP may be a non-TE LSP (i.e. LDP) in
some cases. As described in previous sub-section, it may be
difficult to guarantee an end-to-end QoS in some cases.
CE0/CE1 requests an e2e TE LSP path to CE3/CE2 with the bandwidth
reservation of X. At PE1, this reservation request received in the
context of a VRF will get aggregated onto a pre-established P-TE
LSP, or trigger the establishment of a new P-TE LSP. It should be
noted that C-TE LSPs across different BGP/MPLS IP-VPNs can be
aggregated onto the same P-TE LSP between the same PE pair,
achieving further scalability.
The RSVP-TE control messages (e.g. a RSVP PATH message and a RSVP
RESV message) exchanged among CEs are forwarded by a labeled
packet through the BGP/MPLS IP-VPN. After CE0 and/or CE1 receive
a reservation message from CE2 and/or CE3, CE0/CE1 establishes a
C-TE LSP through the BGP/MPLS IP-VPN.
A P-TE LSP is established between PE1 and PE2. This LSP is used
by the VRF instance to forward customer packets within the
BGP/MPLS IP-VPN.
C-TE LSP
<------------------------------------------------------->
or
C-TE LSP
<----------------------------------------->
P-TE LSP
<--------------------------->
............. .............
. --- --- . --- --- --- --- . --- --- .
.|CE0| |CE1|---|PE1|----|P1 |-----|P2 |----|PE2|---|CE2| |CE3|.
. --- --- . --- --- --- --- . --- --- .
............. .............
^ ^
| |
vrf instance vrf instance
<-customer-> <-------BGP/MPLS IP-VPN-------> <-customer->
network network
or or
another another
service provider service provider
network network
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Figure 2 e2e C-TE LSP model
K.Kumaki, et al. [Page 24]
