Internet DRAFT - draft-zheng-l3vpn-pm-analysis
draft-zheng-l3vpn-pm-analysis
Network Working Group L. Zheng
Internet-Draft Z. Li
Intended status: Informational S. Aldrin
Expires: January 4, 2015 Huawei Technologies
B. Parise
Cisco Systems
July 3, 2014
Performance Monitoring Analysis for L3VPN
draft-zheng-l3vpn-pm-analysis-03
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
network model applies, flow identifying is a 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."
This Internet-Draft will expire on January 4, 2015.
Zheng, et al. Expires January 4, 2015 [Page 1]
Internet-Draft PM Analysis for L3VPN July 2014
Copyright Notice
Copyright (c) 2014 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
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirement of L3VPN Performance Monitoring . . . . . . . . . 3
3. Overview of Current Mechanisms for MPLS Networks . . . . . . 4
3.1. Packet Loss and Delay Measurement for MPLS Networks . . . 4
3.2. Synthetic Measurements . . . . . . . . . . . . . . . . . 4
3.3. Real packet Measurements . . . . . . . . . . . . . . . . 5
3.4. Profile for MPLS-based Transport Networks . . . . . . . . 5
4. Challenge for L3VPN Performance Monitoring . . . . . . . . . 5
5. Design Consideration . . . . . . . . . . . . . . . . . . . . 7
5.1. P2P Pseudo Connection . . . . . . . . . . . . . . . . . . 7
5.2. Hierarchy L3VPN . . . . . . . . . . . . . . . . . . . . . 7
5.3. Control Plane . . . . . . . . . . . . . . . . . . . . . . 7
5.4. Data Plane . . . . . . . . . . . . . . . . . . . . . . . 7
5.5. MPLS OAM . . . . . . . . . . . . . . . . . . . . . . . . 7
5.6. QoS . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.7. ECMP . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Manageability Consideration . . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
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 of performance metrics measurement for
Zheng, et al. Expires January 4, 2015 [Page 2]
Internet-Draft PM Analysis for L3VPN July 2014
packet loss, delay, as well as related metrics is essential for
performance monitoring and Service Level Agreement (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 scaling issue with PWs, L3VPN is used either for end-to-end
service delivery, or L2VPN and L3VPN are used in 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, there multipoint-to-
point (MP2P) network model applies, flow identifying is a challenge.
This document summarizes the current performance monitoring
mechanisms for MPLS networks, and analyzes the challenges for L3VPN
performance monitoring. This document also discuss the key points
need to be taken into consideration when designing L3VPN performance
monitoring mechanisms. All references to L3VPN in the document
refers to MPLS L3VPN networks.
2. Requirement of L3VPN Performance Monitoring
The specific user's traffic is usually tranported by the VPN of the
service provider. The performance mornitoring needs to be done on
the aggregation flow beween a pair of VRFs which belong to the same
VPN for a specific user. And the correpsonding performance
mornitoring report should be provided against the Service Level
Agreement (SLA) by the service provider. For example, in the
following figure, the VRF11 and VRF12 belongs to VPN1 which is used
to bear the service traffic for the specific user USER1, and the
VRF21 and VRF22 belongs to VPN2 which is used to bear the service
traffic for the specific user USER2. Then the performance monitoring
needs to be implemented on the aggregation traffic flow between VRF11
and VRF12 for the USER1. And the performance monitoring needs to be
implemented on the aggregation traffic flow between VRF21 and VRF22
for the USER2.
Zheng, et al. Expires January 4, 2015 [Page 3]
Internet-Draft PM Analysis for L3VPN July 2014
+-----+-----+ VPN FLOW 1 +----+-----+
|VRF11| <------------------------> |VRF12|
|-----+ | | +-----+
+--+ | | +---+ | | +--+
|CE|----| PE1 |------| P |------| PE2 |----|CE|
+--+ | | +---+ | | +--+
+-----+ | | +-----+
|VRF21| <------------------------> |VRF22|
+-----+-----+ VPN FLOW 2 +----+-----+
Figure 1: Performance Monitoring between VRFs
In order to facilitate the description, we introduce two
terminologies in this document:
-- VPN flow: a VPN flow is the aggregate traffic flow between an
ingress VRF and an egress VRF belongs to the same VPN.
-- L3VPN Performance Monitoring (PM): L3VPN PM means the performance
mornitoring on a VPN flow.
3. Overview of Current Mechanisms for MPLS Networks
3.1. 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 Loss Measurement (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 mode measurements provide perfect
loss accounting, but may require specialized hardware support and is
only applicable to some LSP types. Inferred measurement provides
only approximate loss measurments but is generally applicable. The
LM and Delay Measurement (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.
3.2. 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
Zheng, et al. Expires January 4, 2015 [Page 4]
Internet-Draft PM Analysis for L3VPN July 2014
perform inferred measurements, the crafted packets have to behave
like data packets and take the same path as data packets.
3.3. 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.
3.4. 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.
4. 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 LDP is not used
and Penultimate Hop Pop (PHP) function is disabled.
But in the case of L3VPN, multipoint-to-point network model applies ,
it makes the identification of a flow a 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
Zheng, et al. Expires January 4, 2015 [Page 5]
Internet-Draft PM Analysis for L3VPN July 2014
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.
Some people may argue this could be solved by using " tunnel label +
private label" for flow identification, but it is not true. In L3VPN
when LDP LSP applies[RFC5036], the LSPs may be merged at any
intermediate nodes along the 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. When
TE LSP applies [RFC3209] in L3VPN, the ingress VRF could be
identified by the " tunnel label + private label" only if no extranet
exist. The egress PE cannot tell 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 VPN. In the extranet VPN, both Site 11 and Site
12 can access to Site 1. But Site 11 and Site 12 cannot access to
each other. Then VRF1 on PE1 allocates the same label L for the
specific prefix to VRF11 and VRF12 on PE2. Thus when PE1 receives
the VPN flow from PE3, it cannot tell if the flow is from VRF11 or
VRF12 by the label stack.
+------+ +------------+ +-------------+ +------+
| SITE |----+----| PE1 +----+ PE3 +-----+-----+ SITE |
| 1 | |VRF1| | | |VRF13| | 13 |
+------+ +----+------------+ +------+------+-----+ +------+
| |
| |
| +------+------+
+----------+ PE2 |
| |
+-----+-+-----+
|VRF11| |VRF12|
+-----+ +-----+
| |
| |
+------+ +------+
| SITE | | SITE |
| 11 | | 12 |
+------+ +------+
Figure3: Extranet VPN on Ingress PE
The current label allocation mechanism of L3VPN makes the flow
identification a challenge for L3VPN performance monitoring, as a
result the current performance monitoring mechanisms for MPLS
networks cannot be applied to L3VPN networks. Without any backward
compatible extensions or alteration to current label allocation
Zheng, et al. Expires January 4, 2015 [Page 6]
Internet-Draft PM Analysis for L3VPN July 2014
mechanisms, performance measurements cannot be performed in L3VPN
networks.
5. Design Consideration
This section discuss the key points need to be taken in consideration
when designing L3VPN performance monitoring mechanism.
5.1. P2P Pseudo 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 uniquely
identify the ingress VRF, i.e. to establish the Point-to-Point pseudo
connection between the two VRFs. Current allocation mechanism may
need extension or alteration to help build up the Point-to-Point
pseudo connection. Once the Point-to-Point pesudo connection is
built up, current measurement mechanisms may be applied to L3VPN .
5.2. Hierarchy L3VPN
There are flexible hierarchy L3VPN deployment scenarios such as
inter-AS, carrier's carrier, etc. [RFC4364]. The the design of LM
and DM mechanisms should take these scenarios into account.
5.3. 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 pseudo 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.
5.4. Data Plane
Same as for control plane, for compatibility reason, the data plane
should as far as possible be compatible with the current L3VPN
forwarding procedure.
5.5. MPLS OAM
[RFC6374], [RFC6375]defines procedure and protocol mechanisms to
enable the measurement of packet loss, delay, as well as related
metrics for MPLS networks. These mechanisms SHOULD be reasonably
reused in L3VPN networks. The addressing of source an destination of
Zheng, et al. Expires January 4, 2015 [Page 7]
Internet-Draft PM Analysis for L3VPN July 2014
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.
5.6. QoS
Performing the packet loss or delay measurement in L3VPN network,
either proactive or on-demand, SHOULD NOT impact the customer QoS
experience.
5.7. 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
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.
6. Manageability Consideration
[RFC6374] describes manageability consideration of packet loss and
delay measurement for MPLS network. The defined mechanisms should be
reused for L3VPN PM.
7. Security Considerations
This document does not change the security properties of L3VPN.
8. IANA Considerations
This document makes no request to IANA.
Zheng, et al. Expires January 4, 2015 [Page 8]
Internet-Draft PM Analysis for L3VPN July 2014
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.
[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
Zheng, et al. Expires January 4, 2015 [Page 9]
Internet-Draft PM Analysis for L3VPN July 2014
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
Bhavani Parise
Cisco Systems
Email: bhavani@cisco.com
Zheng, et al. Expires January 4, 2015 [Page 10]
