wdiff rfc6965v4.txt rfc6965.txt

Internet Engineering Task Force (IETF) L. Fang, Ed.
Request for Comments: 6965 Cisco
Category: Informational N. Bitar
ISSN: 2070-1721 Verizon
R. Zhang
Alcatel-Lucent
M. Daikoku
KDDI
P. Pan
Infinera
June
July 2013

MPLS Transport Profile (MPLS-TP) Applicability: Use Cases and Design

Abstract

This document describes the applicability of the MPLS Transport
Profile (MPLS-TP) with use case studies and network design
considerations. The use cases include Metro Ethernet access and
aggregation transport, mobile backhaul, and packet optical transport.

Status of This Memo

This document is not an Internet Standards Track specification; it is
published for informational purposes.

This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.

Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6965.

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
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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 ....................................................3
1.1. Terminology ................................................3
1.2. Background .................................................4
2. MPLS-TP Use Cases ...............................................6
2.1. Metro Access and Aggregation ...............................6
2.2. Packet Optical Transport ...................................7
2.3. Mobile Backhaul ............................................8
2.3.1. 2G and 3G Mobile Backhaul ...........................8
2.3.2. 4G/LTE Mobile Backhaul ..............................9
3. Network Design Considerations ..................................10
3.1. The Role of MPLS-TP .......................................10
3.2. Provisioning Mode .........................................10
3.3. Standards Compliance ......................................10
3.4. End-to-End MPLS OAM Consistency ...........................11
3.5. PW Design Considerations in MPLS-TP Networks ..............11
3.6. Proactive and On-Demand MPLS-TP OAM Tools .................12
3.7. MPLS-TP and IP/MPLS Interworking Considerations ...........12
4. Security Considerations ........................................13
5. Acknowledgements ...............................................13
6. References .....................................................13
6.1. Normative References ......................................13
6.2. Informative References ....................................14
7. Contributors ...................................................15

1. Introduction

This document describes the applicability of the MPLS Transport
Profile (MPLS-TP) with use case studies and network design
considerations.

1.1. Terminology

Term Definition
------ -------------------------------------------------------
2G 2nd generation wireless telephone technology
3G 3rd generation of mobile telecommunications technology
4G 4th Generation Mobile network
ADSL Asymmetric Digital Subscriber Line
AIS Alarm Indication Signal
ATM Asynchronous Transfer Mode
BFD Bidirectional Forwarding Detection
BTS Base Transceiver Station
CC-V Continuity Check and Connectivity Verification
CDMA Code Division Multiple Access
E-LINE Ethernet line; provides point-to-point connectivity
E-LAN Ethernet LAN; provides multipoint connectivity
eNB Evolved Node B
EPC Evolved Packet Core
E-VLAN Ethernet Virtual Private LAN
EVDO Evolution-Data Optimized
G-ACh Generic Associated Channel
GAL G-ACh Label
GMPLS Generalized Multi-Protocol Label Switching
GSM Global System for Mobile Communications
HSPA High-Speed High Speed Packet Access
IPTV Internet Protocol television
L2VPN Layer 2 Virtual Private Network
L3VPN Layer 3 Virtual Private Network
LAN Local Access Network
LDI Link Down Indication
LDP Label Distribution Protocol
LSP Label Switched Path
LTE Long-Term Long Term Evolution
MEP Maintenance Entity Group End Point
MIP Maintenance Entity Group Intermediate Point
MPLS Multiprotocol Label Switching
MPLS-TP MPLS Transport Profile
MS-PW Multi-Segment Pseudowire
NMS Network Management System
OAM Operations, Administration, and Maintenance
PE Provider-Edge device
PW Pseudowire
RAN Radio Access Network
RDI Remote Defect Indication
S-PE PW Switching Provider Edge
S1 LTE Standardized interface between eNB and EPC
SDH Synchronous Digital Hierarchy
SONET Synchronous Optical Network
SP Service Provider
SRLG Shared Risk Link Groups
SS-PW Single-Segment Pseudowire
TDM Time-Division Multiplexing
TFS Time and Frequency Synchronization
tLDP Targeted Label Distribution Protocol
UMTS Universal Mobile Telecommunications System
VPN Virtual Private Network
X2 LTE Standardized interface between eNBs for handover

1.2. Background

Traditional transport technologies include SONET/SDH, TDM, and ATM.
There is a transition away from these transport technologies to new
packet transport technologies. In addition to the increasing demand
for bandwidth, packet transport technologies offer the following key
advantages:

Bandwidth efficiency:

Traditional TDM transport technologies support fixed bandwidth, bandwidth with
no statistical multiplexing. The bandwidth is reserved in the
transport network, regardless of whether or not it is used by the
client. In contrast, packet technologies support statistical
multiplexing. This is the most important motivation for the
transition from traditional transport technologies to packet
transport technologies. The proliferation of new distributed
applications that communicate with servers over the network in a
bursty fashion has been driving the adoption of packet transport
techniques, since packet multiplexing of traffic from bursty sources
provides more efficient use of bandwidth than traditional circuit-based circuit-
based TDM technologies.

Flexible data rate connections:

The granularity of data rate connections of traditional transport
technologies is limited to the rigid Plesiochronous Digital Hierarchy
(PDH) hierarchy (e.g., DS1, DS3) or SONET hierarchy (e.g., OC3,
OC12). Packet technologies support flexible data rate connections.
The support of finer data rate granularity is particularly important
for today's wireline and wireless services and applications.

QoS support:

Traditional TDM transport technologies (such as TDM) provide fixed bandwidth
guarantees
guarantees, but they are transparent to unaware of the type types of traffic they carry.
They are not packet aware and do not provide differentiated packet-level services.
Packet transport can provide the differentiated services capability
needed when supporting oversubscription to take advantage of
statistical multiplexing support oversubscription and to deal with traffic
prioritization upon
congestion. congestion: issues that arise only in packet
networks.

The root cause for transport moving to packet transport is the shift
of applications from TDM to packet -- for example, Voice TDM to VoIP,
Video to Video over IP, TDM access lines to Ethernet, and TDM VPNs to
IP VPNs and Ethernet VPNs. In addition, network convergence and
technology refreshes contribute to the demand for a common and
flexible infrastructure that provides multiple services.

As part of the MPLS family, MPLS-TP complements existing IP/MPLS
technologies; it closes the gaps in the traditional access and
aggregation transport to enable end-to-end packet technology
solutions in a cost efficient, reliable, and interoperable manner.
After several years of industry debate on which packet technology to
use, MPLS-TP has emerged as the next generation transport technology
of choice for many Service Providers worldwide.

The Unified MPLS strategy -- using MPLS from core to aggregation and
access (e.g., IP/MPLS in the core, IP/MPLS or MPLS-TP in aggregation
and access) -- appears to be very attractive to many SPs. It
streamlines the operation, reduces the overall complexity, and
improves end-to-end convergence. It leverages the MPLS experience
and enhances the ability to support revenue-generating services.

MPLS-TP is a subset of MPLS functions that meet the packet transport
requirements defined in [RFC5654]. This subset includes: MPLS data
forwarding, pseudowire encapsulation for circuit emulation, and
dynamic control plane using GMPLS control for LSP and tLDP for
pseudowire (PW). MPLS-TP also extends previous MPLS OAM functions,
such as the BFD extension for proactive Connectivity Check and
Connectivity Verification (CC-V) [RFC6428], Remote Defect Indication
(RDI) [RFC6428], and LSP Ping Extension for on-demand CC-V [RFC6426].
New tools have been defined for alarm suppression with Alarm
Indication Signal (AIS) [RFC6427] and switch-over triggering with
Link Down Indication (LDI) [RFC6427]. Note that since the MPLS OAM
feature extensions defined through the process of MPLS-TP development
are part of the MPLS family, the applicability is general to MPLS and
not limited to MPLS-TP.

The requirements of MPLS-TP are provided in the MPLS-TP requirements
document [RFC5654], and the architectural framework is defined in the
MPLS-TP framework document [RFC5921]. This document's intent is to
provide the use case studies and design considerations from a
practical point of view based on Service Providers' deployments plans
as well as actual deployments.

The most common use cases for MPLS-TP include Metro access and
aggregation, mobile backhaul, and packet optical transport. MPLS-TP
data-plane architecture, path protection mechanisms, and OAM
functionality are used to support these deployment scenarios.

The design considerations discussed in this document include the role
of MPLS-TP in the network, provisioning options, standards
compliance, end-to-end forwarding and OAM consistency, compatibility
with existing IP/MPLS networks, and optimization vs. simplicity
design trade-offs.

2. MPLS-TP Use Cases

2.1. Metro Access and Aggregation

The use of MPLS-TP for Metro access and aggregation transport is the
most common deployment scenario observed in the field.

Some operators are building green-field access and aggregation
transport infrastructure, while others are upgrading or replacing
their existing transport infrastructure with new packet technologies.
The existing legacy access and aggregation networks are usually based
on TDM or ATM technologies. Some operators are replacing these
networks with MPLS-TP technologies, since legacy ATM/TDM aggregation
and access are becoming inadequate to support the rapid business
growth and too expensive to maintain. In addition, in many cases the
legacy devices are facing End of Sale and End of Life issues. As
operators must move forward with the next-generation packet
technology, the adoption of MPLS-TP in access and aggregation becomes
a natural choice. The statistical multiplexing in MPLS-TP helps to
achieve higher efficiency compared with the time-division scheme in
the legacy technologies. MPLS-TP OAM tools and protection mechanisms
help to maintain high reliability of transport networks and achieve
fast recovery.

As most Service Providers' core networks are MPLS enabled, extending
the MPLS technology to the aggregation and access transport networks
with a Unified MPLS strategy is very attractive to many Service
Providers. Unified MPLS strategy in this document means having
end-to-end MPLS technologies through core, aggregation, and access.
It reduces operating expenses by streamlining the operation and
leveraging the operational experience already gained with MPLS
technologies; it also improves network efficiency and reduces end-to-
end convergence time.

The requirements from the SPs for ATM/TDM aggregation replacement
often include:

- maintaining the previous operational model, which means providing
a similar user experience in NMS,

- supporting the existing access network (e.g., Ethernet, ADSL, ATM,
TDM, etc.) and connections with the core networks, and

- supporting the same operational capabilities and services (L3VPN,
L2VPN, E-LINE/E-LAN/E-VLAN, Dedicated Line, etc.).

MPLS-TP can meet these requirements and, in general, the requirements
defined in [RFC5654] to support a smooth transition.

2.2. Packet Optical Transport

Many SPs' transport networks consist of both packet and optical
portions. The transport operators are typically sensitive to network
deployment cost and operational simplicity. MPLS-TP supports both
static provisioning through NMS and dynamic provisioning via the
GMPLS control plane. As such, it is viewed as a natural fit in
transport networks where the operators can utilize the MPLS-TP LSPs
(including the ones statically provisioned) to manage user traffic as
"circuits" in both packet and optical networks. Also, when the
operators are ready, they can migrate the network to use the dynamic
control plane for greater efficiency.

Among other attributes, bandwidth management, protection/recovery,
and OAM are critical in packet/optical transport networks. In the
context of MPLS-TP, LSPs may be associated with bandwidth allocation
policies. OAM is to be performed on each individual LSP. For some
of the performance monitoring functions, the OAM mechanisms need to
be able to transmit and process OAM packets at very high frequency.
An overview of the MPLS-TP OAM toolset is found in [RFC6669].

Protection, as defined in [RFC6372], is another important element in
transport networks. Typically, ring and linear protection can be
readily applied in metro networks. However, as long-haul networks
are sensitive to bandwidth cost and tend to have mesh-like topology,
shared mesh protection is becoming increasingly important.

In some cases, SPs plan to deploy MPLS-TP from their long-haul
optical packet transport all the way to the aggregation and access in
their networks.

2.3. Mobile Backhaul

Wireless communication is one of the fastest growing areas in
communication worldwide. In some regions, the tremendous mobile
growth is fueled by the lack of existing landline and cable
infrastructure. In other regions, the introduction of smart phones
is quickly driving mobile data traffic to become the primary mobile
bandwidth consumer (some SPs have already observed that more than 85%
of total mobile traffic is data traffic). MPLS-TP is viewed as a
suitable technology for mobile backhaul.

2.3.1. 2G and 3G Mobile Backhaul

MPLS-TP is commonly viewed as a very good fit for 2G/3G mobile
backhaul. 2G (GSM/CDMA) and 3G (UMTS/HSPA/1xEVDO) mobile backhaul
networks are still currently dominating the mobile infrastructure.

The connectivity for 2G/3G networks is point to point (P2P). The
logical connections have a hub-and-spoke configuration. Networks are
physically constructed using a star or ring topology. In the Radio
Access Network (RAN), each mobile Base Transceiver Station (BTS/Node
B) is communicating with a Base Station Controller (BSC) or Radio
Network Controller (RNC). These connections are often statically set
up.

Hierarchical or centralized architectures are often used for
pre-aggregation and aggregation layers. Each aggregation network
interconnects with multiple access networks. For example, a single
aggregation ring could aggregate traffic for 10 access rings with a
total of 100 base stations.

The technology used today is largely ATM based. Mobile providers are
replacing the ATM RAN infrastructure with newer packet technologies.
IP RAN networks with IP/MPLS technologies are deployed today by many
SPs with great success. MPLS-TP is another suitable choice for
Mobile RAN. The P2P connections from base station to Radio
Controller can be set statically to mimic the operation of today's
RAN environments; in-band OAM and deterministic path protection can
support fast failure detection and switch-over to satisfy service
level agreements (SLAs). Bidirectional LSPs may help to simplify the
provisioning process. The deterministic nature of MPLS-TP LSP setup
can also support packet-based synchronization to maintain predictable
performance regarding packet delay and jitter. The traffic-
engineered and co-routed bidirectional properties of an MPLS-TP LSP
are of benefit in transporting packet-based Time and Frequency
Synchronization (TFS) protocols, such as [TICTOC]. However, the
choice between an external, physical-layer method or a packet-based
TFS method is network dependent and thus is out of scope of this
document.

2.3.2. 4G/LTE Mobile Backhaul

One key difference between LTE and 2G/3G mobile networks is that the
logical connection in LTE is a mesh, while in 2G/3G it is a P2P star.
In LTE, each base station (eNB/BTS) communicates with multiple
network controllers (e.g., Packet Data Network Gateway, Packet Data
Network Serving Gateway, Access Service Network Gateway), and the
radio elements communicate with one another for signal exchange and
traffic offload to wireless or wireline infrastructures.

IP/MPLS has a great advantage in any-to-any connectivity
environments. Thus, the use of mature IP or L3VPN technologies is
particularly common in the design of an SP's LTE deployment plans.

The extended OAM functions defined in MPLS-TP, such as in-band OAM
and path protection mechanisms, bring additional advantages to
support SLAs. The dynamic control plane with GMPLS signaling is
especially suited for the mesh environment, to support dynamic
topology changes and network optimization.

Some operators are using the same model as in 2G and 3G mobile
backhaul, which uses IP/MPLS in the core and MPLS-TP with static
provisioning (through NMS) in aggregation and access. The reasoning
is as follows: currently, the X2 traffic load in LTE networks may be
a very small percentage of the total traffic. For example, one large
mobile operator observed that X2 traffic was less than one percent of
the total S1 traffic. Therefore, optimizing the X2 traffic may not
be the design objective in this case. The X2 traffic can be carried
through the same static tunnels together with the S1 traffic in the
aggregation and access networks and further forwarded across the
IP/MPLS core. In addition, mesh protection may be more efficient
with regard to bandwidth utilization, but linear protection and ring
protection are often considered simpler by some operators from the
point of view of operation maintenance and troubleshooting, and so
are widely deployed. In general, using MPLS-TP with static
provisioning for LTE backhaul is a viable option. The design
objective of using this approach is to keep the operation simple and
use a common model for mobile backhaul, especially during the
transition period.

The TFS considerations stated in Section 2.3.1 apply to the 4G/LTE
mobile backhaul case as well.

3. Network Design Considerations

3.1. The Role of MPLS-TP

The role of MPLS-TP is to provide a solution to help evolve
traditional transport towards packet transport networks. It is
designed to support the transport characteristics and behavior
described in [RFC5654]. The primary use of MPLS-TP is largely to
replace legacy transport technologies, such as SONET/SDH. MPLS-TP is
not designed to replace the service support capabilities of IP/MPLS,
such as L2VPN, L3VPN, IPTV, Mobile RAN, etc.

3.2. Provisioning Mode

MPLS-TP supports two provisioning modes:

- a mandatory static provisioning mode, which must be supported
without dependency on dynamic routing or signaling; and

- an optional distributed dynamic control plane, which is used to
enable dynamic service provisioning.

The decision on which mode to use is largely dependent on the
operational feasibility and the stage of network transition.
Operators who are accustomed to the transport-centric operational
model (e.g., NMS configuration without control plane) typically
prefer the static provisioning mode. This is the most common choice
in current deployments. The dynamic provisioning mode can be more
powerful, but it is more suited to operators who are familiar with
the operation and maintenance of IP/MPLS technologies or are ready to
step up through training and planned transition.

There may also be cases where operators choose to use the combination
of both modes. This is appropriate when parts of the network are
provisioned in a static fashion, and other parts are controlled by
dynamic signaling. This combination may also be used to transition
from static provisioning to dynamic control plane.

3.3. Standards Compliance

SPs generally recognize that standards compliance is important for
lowering cost, accelerating product maturity, achieving multi-vendor
interoperability, and meeting the expectations of their enterprise
customers.

MPLS-TP is a joint work between the IETF and ITU-T. In April 2008,
the IETF and ITU-T jointly agreed to terminate T-MPLS and progress
MPLS-TP as joint work [RFC5317]. The transport requirements are
provided by the ITU-T; the protocols are developed in the IETF.

3.4. End-to-End MPLS OAM Consistency

End-to-end MPLS OAM consistency is highly desirable in order to
enable Service Providers to deploy an end-to-end MPLS solution. As
MPLS-TP adds OAM function to the MPLS toolkit, it cannot be expected
that a full-function end-to-end LSP with MPLS-TP OAM can be achieved
when the LSP traverses a legacy MPLS/IP core. Although it may be
possible to select a subset of MPLS-TP OAM that can be gatewayed to
the legacy MPLS/IP OAM, a better solution is achieved by tunneling
the MPLS-TP LSP over the legacy MPLS/IP network. In that mode of
operation, legacy OAM may be run on the tunnel in the core, and the
tunnel endpoints may report issues in as much detail as possible to
the MIPs in the MPLS-TP LSP. Note that over time it is expected that
routers in the MPLS/IP core will be upgraded to fully support MPLS-TP
features. Once this has occurred, it will be possible to run
end-to-end MPLS-TP LSPs seamlessly across the core.

3.5. PW Design Considerations in MPLS-TP Networks

In general, PWs in MPLS-TP work the same as in IP/MPLS networks.
Both Single-Segment PW (SS-PW) and Multi-Segment PW (MS-PW) are
supported. For dynamic control plane, Targeted LDP (tLDP) is used.
In static provisioning mode, PW status is a new PW OAM feature for
failure notification. In addition, both directions of a PW must be
bound to the same transport bidirectional LSP.

In the common network topology involving multi-tier rings, the design
choice is between using SS-PW or MS-PW. This is not a discussion
unique to MPLS-TP, as it applies to PW design in general. However,
it is relevant here, since MPLS-TP is more sensitive to the
operational complexities, as noted by operators. If MS-PW is used,
Switching PE (S-PE) must be deployed to connect the rings. The
advantage of this choice is that it provides domain isolation, which
in turn facilitates troubleshooting and allows for faster PW failure
recovery. On the other hand, the disadvantage of using S-PE is that
it adds more complexity. Using SS-PW is simpler, since it does not
require S-PEs, but it is less efficient because the paths across
primary and secondary rings are longer. If operational simplicity is
a higher priority, some SPs choose SS-PW.

Another design trade-off is whether to use PW protection in addition
to LSP protection or rely solely on LSP protection. When the MPLS-TP
LSPs are protected, if the working LSP fails, the protecting LSP
assures that the connectivity is maintained and the PW is not
impacted. However, in the case of simultaneous failure of both the
working and protecting LSPs, the attached PW would fail. By adding
PW protection and attaching the protecting PW to a diverse LSP not in
the same Shared Risk Link Group (SRLG), the PW is protected even when
the primary PW fails. Clearly, using PW protection adds considerably
more complexity and resource usage, and thus operators often may
choose not to use it and consider protection against a single point
of failure as sufficient.

3.6. Proactive and On-Demand MPLS-TP OAM Tools

MPLS-TP provides both proactive and on-demand OAM tools. As a
proactive OAM fault management tool, BFD Connectivity Check (CC) can
be sent at regular intervals for Connectivity Check; three (or a
configurable number) of missed CC messages can trigger the failure
protection switch-over. BFD sessions are configured for both working
and protecting LSPs.

A design decision is choosing the value of the BFD CC interval. The
shorter the interval, the faster the detection time is, but also the
higher the resource utilization is. The proper value depends on the
application and the service needs, as well as the protection
mechanism provided at the lower layer.

As an on-demand OAM fault management mechanism (for example, when
there is a fiber cut), a Link Down Indication (LDI) message [RFC6427]
can be generated from the failure point and propagated to the
Maintenance Entity Group End Points (MEPs) to trigger immediate
switch-over from working to protecting path. An Alarm Indication
Signal (AIS) can be propagated from the Maintenance Entity Group
Intermediate Point (MIP) to the MEPs for alarm suppression.

In general, both proactive and on-demand OAM tools should be enabled
to guarantee short switch-over times.

3.7. MPLS-TP and IP/MPLS Interworking Considerations

Since IP/MPLS is largely deployed in most SPs' networks, MPLS-TP and
IP/MPLS interworking is inevitable if not a reality. However,
interworking discussion is out of the scope of this document; it is
for further study.

4. Security Considerations

Under the use case of Metro access and aggregation, in the scenario
where some of the access equipment is placed in facilities not owned
by the SP, the static provisioning mode of MPLS-TP is often preferred
over the control-plane option because it eliminates the possibility
of a control-plane attack, which may potentially impact the whole
network. This scenario falls into the Security Reference Model 2 as
described in [RFC6941].

Similar location issues apply to the mobile use cases since equipment
is often placed in remote and outdoor environment, which can increase
the risk of unauthorized access to the equipment.

In general, NMS access can be a common point of attack in all MPLS-TP
use cases, and attacks to GAL or G-ACh are unique security threats to
MPLS-TP. The MPLS-TP security considerations are discussed in the
MPLS-TP security framework [RFC6941]. General security
considerations for MPLS and GMPLS networks are addressed in "Security
Framework for MPLS and GMPLS Networks" [RFC5920].

5. Acknowledgements

The authors wish to thank Adrian Farrel for his review as Routing
Area Director and his continued support and guidance. Adrian's
detailed comments and suggestions were of great help for improving
the quality of this document. In addition, the authors would like to
thank the following individuals: Loa Andersson for his continued
support and guidance; Weiqiang Cheng for his helpful input on LTE
mobile backhaul based on his knowledge and experience in real world
deployment; Stewart Bryant for his text contribution on timing; Russ
Housley for his improvement suggestions; Andrew Malis for his support
and use case discussion; Pablo Frank, Lucy Yong, Huub van Helvoort,
Tom Petch, Curtis Villamizar, and Paul Doolan for their comments and
suggestions; and Joseph Yee and Miguel Garcia for their APPSDIR and
Gen-ART reviews and comments, respectively.

6. References

6.1. Normative References

[RFC5654] Niven-Jenkins, B., Ed., Brungard, D., Ed., Betts, M., Ed.,
Sprecher, N., and S. Ueno, "Requirements of an MPLS
Transport Profile", RFC 5654, September 2009.

[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, July 2010.

[RFC5921] Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau,
L., and L. Berger, "A Framework for MPLS in Transport
Networks", RFC 5921, July 2010.

[RFC6426] Gray, E., Bahadur, N., Boutros, S., and R. Aggarwal, "MPLS
On-Demand Connectivity Verification and Route Tracing",
RFC 6426, November 2011.

[RFC6427] Swallow, G., Ed., Fulignoli, A., Ed., Vigoureux, M., Ed.,
Boutros, S., and D. Ward, "MPLS Fault Management
Operations, Administration, and Maintenance (OAM)", RFC
6427, November 2011.

[RFC6428] Allan, D., Ed., Swallow Ed., G., and J. Drake Ed.,
"Proactive Connectivity Verification, Continuity Check,
and Remote Defect Indication for the MPLS Transport
Profile", RFC 6428, November 2011.

6.2. Informative References

[RFC5317] Bryant, S., Ed., and L. Andersson, Ed., "Joint Working
Team (JWT) Report on MPLS Architectural Considerations for
a Transport Profile", RFC 5317, February 2009.

[RFC6372] Sprecher, N., Ed., and A. Farrel, Ed., "MPLS Transport
Profile (MPLS-TP) Survivability Framework", RFC 6372,
September 2011.

[RFC6669] Sprecher, N. and L. Fang, "An Overview of the Operations,
Administration, and Maintenance (OAM) Toolset for MPLS-
Based Transport Networks", RFC 6669, July 2012.

[RFC6941] Fang, L., Ed., Niven-Jenkins, B., Ed., Mansfield, S., Ed.,
and R. Graveman, Ed., "MPLS Transport Profile (MPLS-TP)
Security Framework", RFC 6941, April 2013.

[TICTOC] Davari, S., Oren, A., Bhatia, M., Roberts, P., Montini,
L., and L.
Montini, Martini, "Transporting Timing messages over
MPLS Networks", Work in Progress, February June 2013.

7. Contributors

Kam Lee Yap
XO Communications
13865 Sunrise Valley Drive
Herndon, VA 20171
United States
EMail: klyap@xo.com

Dan Frost
Cisco Systems, Inc.
United Kingdom
EMail: danfrost@cisco.com

Henry Yu
TW Telecom
10475 Park Meadow Dr.
Littleton, CO 80124
United States
EMail: henry.yu@twtelecom.com

Jian Ping Zhang
China Telecom, Shanghai
Room 3402, 211 Shi Ji Da Dao
Pu Dong District, Shanghai
China
EMail: zhangjp@shtel.com.cn

Lei Wang
Lime Networks
Strandveien 30, 1366 Lysaker
Norway
EMail: lei.wang@limenetworks.no

Mach (Guoyi) Chen
Huawei Technologies Co., Ltd.
No. 3 Xinxi Road
Shangdi Information Industry Base
Hai-Dian District, Beijing 100085
China
EMail: mach@huawei.com

Nurit Sprecher
Nokia Siemens Networks
3 Hanagar St. Neve Ne'eman B
Hod Hasharon, 45241
Israel
EMail: nurit.sprecher@nsn.com

Authors' Addresses

Luyuan Fang (editor)
Cisco Systems, Inc.
111 Wood Ave. South
Iselin, NJ 08830
United States
EMail: lufang@cisco.com

Nabil Bitar
Verizon
40 Sylvan Road
Waltham, MA 02145
United States
EMail: nabil.bitar@verizon.com

Raymond Zhang
Alcatel-Lucent
701 Middlefield Road
Mountain View, CA 94043
United States
EMail: raymond.zhang@alcatel-lucent.com

Masahiro Daikoku
KDDI Corporation
3-11-11.Iidabashi, Chiyodaku, Tokyo
Japan
EMail: ms-daikoku@kddi.com

Ping Pan
Infinera
United States
EMail: ppan@infinera.com