Performance Monitoring Analysis for L3VPN
draft-zheng-l3vpn-pm-analysis-00
The information below is for an old version of the document.
| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Lianshu Zheng , Zhenbin Li | ||
| Last updated | 2012-10-15 | ||
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draft-zheng-l3vpn-pm-analysis-00
Network Working Group L. Zheng
Internet-Draft Z. Li
Intended status: Standards Track Huawei Technologies
Expires: April 18, 2013 October 15, 2012
Performance Monitoring Analysis for L3VPN
draft-zheng-l3vpn-pm-analysis-00
Abstract
To perform the measurement of packet loss, delay and other metrics on
a particular VPN flow, the egress PE need to tell to which specific
ingress VRF a packet belongs. But for L3VPN, multipoint-to-point or
multipoint-to-multipoint (MP2MP) network model applies, flow
identifying is a big challenge. This document summarizes the current
performance monitoring mechanisms for MPLS networks, and analyzes the
challenge for L3VPN performance monitoring. This document also
discuss the key points need to be taken in consideration when
designing L3VPN performance monitoring mechanisms.
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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 RFC 2119 [RFC2119].
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 18, 2013.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Overview of current mechanisms for MPLS networks . . . . . . . 5
2.1. Packet Loss and Delay Measurement for MPLS Networks . . . 5
2.2. Profile for MPLS-based Transport Networks . . . . . . . . 5
3. Challenge for L3VPN Performance Monitoring . . . . . . . . . . 6
4. Design Consideration . . . . . . . . . . . . . . . . . . . . . 8
4.1. P2P Connection . . . . . . . . . . . . . . . . . . . . . . 8
4.2. Control Plane . . . . . . . . . . . . . . . . . . . . . . 8
4.3. Data Plane . . . . . . . . . . . . . . . . . . . . . . . . 8
4.4. MPLS OAM . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.5. QoS . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.6. Configuration . . . . . . . . . . . . . . . . . . . . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
8.1. Normative References . . . . . . . . . . . . . . . . . . . 13
8.2. Informative References . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
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1. Introduction
Level 3 Virtual Private Network (L3VPN) [RFC4364]service is widely
deployed in the production network. It is deployed to provide
enterprise interconnection, Voice over IP (VoIP), video, mobile, etc.
services. Most of these services are sensitive to the packet loss
and delay. The capability to measure and monitor performance metrics
for packet loss, delay, as well as related metrics is essential for
SLA. The requirement for SLA measurement for MPLS networks has been
documented in [RFC4377].
One popular deployment of L3VPN nowadays is in mobile backhaul
networks. When deploying MPLS-TP in mobile backhaul network, due to
the scalability issue with PW, L3VPN is used either for end-to-end
service delivery, or L2VPN and L3VPN hybrid networking. The
measurement capability of L3VPN provides operators with greater
visibility into the performance characteristics of their networks,
and provides diagnostic information in case of performance
degradation or failure and helps for fault localization.
To perform the measurement of packet loss, delay and other metrics on
a particular VPN flow, the egress PE need to tell to which specific
ingress VRF a packet belongs. But for L3VPN, multipoint-to-point or
multipoint-to-multipoint (MP2MP) network model applies, flow
identifying is a big challenge. This document summarizes the current
performance monitoring mechanisms for MPLS networks, and analyzes the
challenge for L3VPN performance monitoring. This document also
discuss the key points need to be taken in consideration when
designing L3VPN performance monitoring mechanisms.
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2. Overview of current mechanisms for MPLS networks
2.1. Packet Loss and Delay Measurement for MPLS Networks
[RFC6374]defines procedure and protocol mechanisms to enable the
efficient and accurate measurement of packet loss, delay, as well as
related metrics in MPLS networks.
The LM protocol can perform two distinct kinds of loss measurement.
In inferred mode, it can measure the loss of specially generated test
packets (in order to infer the approximate data-plane loss level).
In direct mode, it can directly measure data-plane packet loss.
Direct measurement provides perfect loss accounting, but may require
specialized hardware support and is only applicable to some LSP
types. Inferred measurement provides only approximate loss
accounting but is generally applicable.
The LM and DM protocols are initiated from a single node, the
querier. A query message may be received either by a single node or
by multiple nodes; i.e. these protocols provide point-to-point or
point-to-multipoint measurement capabilities.
2.2. Profile for MPLS-based Transport Networks
Procedures for the measurement of packet loss, delay, and throughput
in MPLS networks are defined in [RFC6374]. [RFC6375]describes a
profile, i.e. a simplified subset, of procedures that suffices to
meet the specific requirements of MPLS-based transport networks
[RFC5921] as defined in [RFC5860]. This profile is presented for the
convenience of implementors who are concerned exclusively with the
transport network context.
LM session is externally configured and the values of several
protocol parameters can be fixed in advance at the endpoints involved
in the session, so that inspection or negotiation of these parameters
is not required.
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3. Challenge for L3VPN Performance Monitoring
To perform the measurement of packet loss, delay and other metrics on
a particular VPN flow, the egress PE need to tell to which specific
ingress VRF a packet belongs.
The above mentioned existing mechanisms for MPLS networks provide
either point-to-point or point-to-multipoint measurement
capabilities. For a specific receiver, it could easily identify a
specific flow by the label stack information, when Penultimate Hop
Pop (PHP) function is disabled .
But in the case of L3VPN, multipoint-to-point or multipoint-to-
multipoint (MP2MP) network model applies , it makes the flow
identifying a big challenge for packets loss and delay measurement.
According to the label allocation mechanisms of L3VPN, a private
label itself cannot uniquely identify a specific VPN flow. That is,
when the egress PE allocates VPN label for a specific prefix of a
VPN, the same label will be advertised to all its peers. Given a VPN
flow, the egress PE cannot tell which ingress VRF is from based on
the private label it carries. As a result, it's not feasible to
perform the loss or delay measurement on this flow.
In L3VPN the LSPs may be merged at any intermediate nodes along the
LSP (e.g., Label Distribution Protocol (LDP) [RFC5036] based LSP).
The egress PE cannot derive a unique identifier of the source PE from
label stack. The tunnel label cannot help for flow identification
due to the LSP merge.
In L3VPN, the ingress PE could be identified by the tunnel label when
TE LSP applies [RFC3209], but the egress PE cannot tell to which
specific VRF a packet belongs when extranet (If the various sites in
a VPN are owned by different enterprises) exist on ingress PE.
Figure 1 shows an example of extranet. In Figure1, Site A,B,C,D all
belong to the same VPN-A, but Site C and Site D does not belong to
the same enterprise (Site D also belongs to a VPN-B), so different
VRFs are maintained for each site on PE3. PE1 assign the same label
L for prefix 10.0.0.1 to PE3 of VPN-A, when it recieve the VPN-A flow
from PE3, it can not tell the flow is from either VRFC or VRFD by the
label stack.
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+------+ +------------+ +-------------+ +------+
| SITE |----+----| PE +---------+ PE +----+-----+ SITE |
| A | |VRFA| 1 | | 2 |VRFB| | B |
+------+ +----+------------+ +------+------+----+ +------+
| |
| VPN-A |
| |
| +------+-----+
+---------------+ PE |
| 3 |
+----+--+----+
|VRFC| |VRFD|
+----+ +----+
| |
| | Extranet VPN-B
+------+ +------+
| SITE | | SITE |
| C | | D +----
+------+ +------+
Figure1: Extranet on Ingress PE
The current label allocation mechanism of L3VPN make the flow
identification a big challenge for L3VPN performace monitoring, as a
result the current performace monitoring mechanisms for MPLS networks
cannot be applied to L3VPN networks. Extension or alteration to
current label allocation mechanism is needed to solve the problem.
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4. Design Consideration
This section discuss the key points need to be taken in consideration
when designing L3VPN performance monitoring mechanism.
4.1. P2P Connection
As analyzed above, to perform the packet loss or delay measurement on
a specific VPN flow, it is critical for the egress PE to identify the
unique ingress VRF, i.e. to establish the Point-to-Point connection
between the two VRFs. Current allocation mechanism may need
extension or alteration to help build up the Point-to-Point
connection. Once the Point-to-Point connection is built up, current
measurement mechanisms may be applied to L3VPN .
Conditions like Penultimate Hop Popping (PHP), Equal-Cost Multi-Path
(ECMP) load-balancing and BGP multi-path may make it infeasible for
receiving PE to identify the ingress PE. These conditions SHOULD be
excluded for consideration for mechanism design.
4.2. Control Plane
In L3VPN, BGP is used to distribute a particular route, as well as an
MPLS label that is mapped to that route [RFC4364]. The label mapping
information for a particular route is piggybacked in the same BGP
Update message that is used to distribute the route itself. In order
to setup the Point-to-Point connection between ingress and egress
VRFs the current label distribution mechanism may be altered. For
compatibility, this alteration SHOULD NOT change the current label
distribution mechanism dramatically.
4.3. Data Plane
Same as for control plane, for compatibility reason, the data plane
should as far as be compatible with the current L3VPN forwarding
procedure.
4.4. MPLS OAM
[RFC6374], [RFC6375]defines procedure and protocol mechanisms to
enable the measurement of packet loss, delay, as well as related
metrics in MPLS networks. These mechanisms SHOULD be reasonably
reused in L3VPN networks. The addressing of source an destination of
Loss Measurement (LM) and Delay Measurement (DM) messages may needed
to be changed to identify the measured VRF.
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4.5. QoS
To perform the packet loss or delay measurement in L3VPN network,
either proactive or on-demand, SHOULD NOT impact the customer QoS
experience.
4.6. Configuration
Measurement entities and functions MUST be configurable either
statically or dynamically. It SHOULD be possible to configure and
activated/deactivated the measurement capability as part of
connectivity establishment, and it SHOULD also be possible to
configure and activated/deactivated the capability after connectivity
has been established .
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5. Security Considerations
This document does not change the security properties of L3VPN.
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6. IANA Considerations
This document makes no request to IANA.
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7. Acknowledgements
The authors would like to thank XXX for their valuable comments.
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8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
8.2. Informative References
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, February 2006.
[RFC4377] Nadeau, T., Morrow, M., Swallow, G., Allan, D., and S.
Matsushima, "Operations and Management (OAM) Requirements
for Multi-Protocol Label Switched (MPLS) Networks",
RFC 4377, February 2006.
[RFC5036] Andersson, L., Minei, I., and B. Thomas, "LDP
Specification", RFC 5036, October 2007.
[RFC5860] Vigoureux, M., Ward, D., and M. Betts, "Requirements for
Operations, Administration, and Maintenance (OAM) in MPLS
Transport Networks", RFC 5860, May 2010.
[RFC5921] Bocci, M., Bryant, S., Frost, D., Levrau, L., and L.
Berger, "A Framework for MPLS in Transport Networks",
RFC 5921, July 2010.
[RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay
Measurement for MPLS Networks", RFC 6374, September 2011.
[RFC6375] Frost, D. and S. Bryant, "A Packet Loss and Delay
Measurement Profile for MPLS-Based Transport Networks",
RFC 6375, September 2011.
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Authors' Addresses
Lianshu Zheng
Huawei Technologies
China
Email: vero.zheng@huawei.com
Zhenbin Li
Huawei Technologies
China
Email: lizhenbin@huawei.com
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