One document matched: draft-zheng-l3vpn-pm-analysis-02.txt
Differences from draft-zheng-l3vpn-pm-analysis-01.txt
Network Working Group L. Zheng
Internet-Draft Z. Li
Intended status: Informational S. Aldrin
Expires: April 21, 2014 Huawei Technologies
B. Parise
Cisco Systems
October 18, 2013
Performance Monitoring Analysis for L3VPN
draft-zheng-l3vpn-pm-analysis-02
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 to. 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 L3VPN in MPLS networks, and
analyzes various solutions and challenges for measuring performance
metrics within these networks. This document also identifies various
key points which needs to be taken in consideration when designing
L3VPN performance monitoring mechanisms. Performance measurements
within non-MPLS L3VPN networks is not within the scope of the
document.
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.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
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This Internet-Draft will expire on April 21, 2014.
Copyright Notice
Copyright (c) 2013 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
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Overview of current mechanisms for MPLS networks . . . . . . 3
2.1. Packet Loss and Delay Measurement for MPLS Networks . . . 3
2.2. Synthetic measurements . . . . . . . . . . . . . . . . . 4
2.3. Real packet measurements . . . . . . . . . . . . . . . . 4
2.4. Profile for MPLS-based Transport Networks . . . . . . . . 4
3. Challenge for L3VPN Performance Monitoring . . . . . . . . . 4
4. Design Consideration . . . . . . . . . . . . . . . . . . . . 6
4.1. P2P Connection . . . . . . . . . . . . . . . . . . . . . 6
4.2. Hierarchy L3VPN . . . . . . . . . . . . . . . . . . . . . 6
4.3. Control Plane . . . . . . . . . . . . . . . . . . . . . . 7
4.4. Data Plane . . . . . . . . . . . . . . . . . . . . . . . 7
4.5. MPLS OAM . . . . . . . . . . . . . . . . . . . . . . . . 7
4.6. QoS . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.7. ECMP . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Manageability Consideration . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
9.1. Normative References . . . . . . . . . . . . . . . . . . 8
9.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
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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 networks, 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. All references to
L3VPN further in the document refers to MPLS L3VPN networks.
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. There should also be
inferred mode and direct mode for LM in the L3VPN environment. This
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document focuses on the direct mode. The inferred mode is out of
scope of the document.
The LM and DM protocols are initiated from a single node. 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. Synthetic measurements
Performance measurements are done using synthetic packets sent over
the network. Metrics like response time, jitter, packet loss could
be inferred using these synthetic packet measurements. In order to
perform inferred measurements, the crafted packets have to behave
like data packets and take the same path as data packets.
2.3. Real packet measurements
Measurements of actual data packets is resource intensive and
requires special way of accounting for the measurements. Counters
within the network devices are primarily used to measure various
metrics. Various technologies like Netflow, IPFIX, etc are used to
collect the data and process it offline to derive performance
measurements.
When the data is aggregated, collecting per flow or per VPN customer
traffic data becomes complex. More details are found in the
subsequent sections.
2.4. 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 implementers 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.
3. Challenge for L3VPN Performance Monitoring
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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 LDP is not used
and 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
identification of a flow, a big challenge, for packet 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 to, 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 receives the VPN-A
flow from PE3, it can not tell the flow is from either VRFC or VRFD
by the label stack.
+------+ +------------+ +-------------+ +------+
| SITE |----+----| PE +---------+ PE +----+-----+ SITE |
| A | |VRFA| 1 | | 2 |VRFB| | B |
+------+ +----+------------+ +------+------+----+ +------+
| |
| VPN-A |
| |
| +------+-----+
+---------------+ PE |
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| 3 |
+----+--+----+
|VRFC| |VRFD|
+----+ +----+
| |
| | Extranet VPN-B
+------+ +------+
| SITE | | SITE |
| C | | D +----
+------+ +------+
Figure1: Extranet on Ingress PE
The current label allocation mechanism of L3VPN makes the flow
identification a big challenge for L3VPN performance monitoring, as a
result the current performance monitoring mechanisms for MPLS
networks cannot be applied to L3VPN networks. Without any extensions
or alteration to current label allocation mechanisms, performance
measurements cannot be performed in L3VPN networks.
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 are to be
considered when designing solutions.
4.2. Hierarchy L3VPN
There are flexible hierarchy L3VPN deployment scenarios such as
inter-AS, carrier's carrier, etc[RFC4364]. The mechanism design
should take into account these scenarios. Since the document focuses
on MPLS transport network which seldom introduces the complex L3VPN
scenarios, it is for further research if more complex mechanisms for
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these hierarchy L3VPN scenarios besides reusing the mechanism for the
simple L3VPN scenarios has to be introduced.
4.3. 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.
4.4. 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.
4.5. 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.
LSP ping and trace based on [RFC4379] are used to perform various
metric measurement which includes jitter etc. Most of the
measurements like response time, jitter, etc., are inferred
measurements with synthetic measurements and not necessarily the true
representation of the data packets traversing the network, especially
with respect to packet loss measurements.
4.6. QoS
To perform the packet loss or delay measurement in L3VPN network,
either proactive or on-demand, SHOULD NOT impact the customer QoS
experience.
4.7. ECMP
Performance measurements within ECMP networks poses a bigger
challenge. When the data packet traverse the network, the logic of
hashing on to a ECMP path is a local decision based on the header
information it is carrying. Number of labels, IP header, UDP header
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could play a role in considering which path the packet traverses.
When PM is measured with synthetic packets, the crafted packets have
to be constructed to ensure various ECMP paths are measured. This
poses a big challenge for the source, which generates these packets,
to reflect the behavior of the actual data traffic and measure the
metrics. [RFC4379] provides various mechanisms to perform LM and DM
measurements over ECMP networks.
5. Manageability Consideration
[RFC6374] describes manageability consideration of packet loss and
delay measurement for MPLS network. The defined mechanisms should be
reused for L3VPN PM.
6. Security Considerations
This document does not change the security properties of L3VPN.
7. IANA Considerations
This document makes no request to IANA.
8. Acknowledgements
The authors would like to thank XXX for their valuable comments.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
9.2. 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.
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[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures", RFC 4379,
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.
Authors' Addresses
Lianshu Zheng
Huawei Technologies
Huawei Building, No.156 Beiqing Rd.
Beijing 100095
China
Email: vero.zheng@huawei.com
Zhenbin Li
Huawei Technologies
Huawei Building, No.156 Beiqing Rd.
Beijing 100095
China
Email: lizhenbin@huawei.com
Sam K. Aldrin
Huawei Technologies
Email: aldrin.ietf@gmail.com
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Bhavani Parise
Cisco Systems
Email: bhavani@cisco.com
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