Network Working Group Luyuan Fang
Internet Draft Dan Frost
Intended status: Informational Cisco Systems
Expires: April 25, 2011 Nabil Bitar
Verizon
Raymond Zhang
BT
Masahiro DAIKOKU
KDDI
Jian Ping Zhang
China Telecom, Shanghai
Lei Wang
Telenor
Mach(Guoyi) Chen
Huawei Technologies
Nurit Sprecher
Nokia Siemens Networks
October 25, 2010
MPLS-TP Use Cases Studies and Design Considerations
draft-fang-mpls-tp-use-cases-and-design-02.txt
Abstract
This document provides use case studies and network design
considerations for Multiprotocol Label Switching Transport Profile
(MPLS-TP).
In the recent years, MPLS-TP has emerged as the technology of choice
to meet the needs of transport evolution. Many service providers
(SPs) intend to replace SONET/SDH, TDM, ATM traditional transport
technologies with MPLS-TP, to achieve higher efficiency, lower
operational cost, while maintaining transport characteristics. The
use cases for MPLS-TP include Mobile backhaul, Metro Ethernet access
and aggregation, and packet optical transport. The design
considerations include operational experience, standards compliance,
technology maturity, end-to-end forwarding and OAM consistency,
compatibility with IP/MPLS networks, and multi-vendor
interoperability. The goal is to provide reliable, manageable, and
scalable transport solutions.
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) appear to be very attractive to many SPs. It streamlines
the operation, many help to reduce the overall complexity and
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MPLS-TP Use Cases Studies and Design Considerations October 2010
improve end-to-end convergence. It leverages the MPLS experience,
and enhances the ability to support revenue generating services.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with
the provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
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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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on January 12, 2011.
Copyright Notice
Copyright (c) 2010 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 in effect on the date of
publication of this document (http://trustee.ietf.org/license-info).
Please review these documents carefully, as they describe your
rights and restrictions with respect to this document.
This document is subject to BCP 78 and the IETF Trust's Legal
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document must include Simplified BSD License text as described in
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MPLS-TP Use Cases Studies and Design Considerations October 2010
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..................................................4
1.1. Background and Motivation..................................4
1.2. Contributing authors.......................................5
2. Terminologies.................................................5
3. Overview of MPLS-TP base functions............................6
3.1. MPLS-TP development principles.............................6
3.2. Data Plane.................................................7
3.3. Control Plane..............................................7
3.4. OAM........................................................7
3.5. Survivability..............................................8
4. MPLS-TP Use Case Studies......................................8
4.1. Mobile Backhaul............................................8
4.2. Metro Access and Aggregation..............................10
4.3. Packet Optical Transport..................................10
5. Network Design Considerations................................11
5.1. IP/MPLS vs. MPLS-TP.......................................11
5.2. Standards compliance......................................11
5.3. End-to-end MPLS OAM consistency...........................12
5.4. Delay and delay variation.................................12
5.5. General network design considerations.....................15
6. MPLS-TP Deployment Consideration.............................15
6.1. Network Modes Selection...................................15
6.2. Provisioning Modes Selection..............................16
7. Security Considerations......................................16
8. IANA Considerations..........................................16
9. Normative References.........................................17
10. Informative References......................................17
11. Author's Addresses..........................................17
Requirements Language
Although this document is not a protocol specification, 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 [RFC
2119].
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MPLS-TP Use Cases Studies and Design Considerations October 2010
1. Introduction
1.1. Background and Motivation
This document provides case studies and network design
considerations for Multiprotocol Label Switching Transport Profile
(MPLS-TP).
In recent years, the urgency for moving from traditional transport
technologies such as SONET/SDH, TDM/ATM to new packet technologies
has been rising. This is largely due to the tremendous success of
data services, such as IPTV and IP Video for content downloading,
streaming, and sharing; rapid growth of mobile services, especially
smart phone applications; business VPNs and residential broadband.
Continued network convergence effort is another contributing factor
for transport moving toward packet technologies. After several years
of heated debate, MPLS-TP has emerged as the next generation
transport technology of choice for many service providers
worldwide.
MPLS-TP is based on MPLS technologies. MPLS-TP re-use a subset of
MPLS base functions, such as MPLS data forwarding, Pseudo-wire
encapsulation for circuit emulation, and GMPLS for control plane
option; MPLS-TP extended current MPLS OAM functions, such as BFD
extension for Connectivity for proactive Connectivity Check (CC) and
Connectivity Verification (CV), and Remote Defect Indication (RDI),
LSP Ping Extension for on demand Connectivity Check (CC) and
Connectivity Verification (CV), fault allocation, and remote
integrity check. New tools are being defined for alarm suppression
with Alarm Indication Signal (AIS), and trigger of switch over with
Link Defect Indication (LDI). The goal is to take advantage of the
maturity of MPLS technology, re-use the existing component when
possible and extend the existing protocols or create new
procedures/protocols when needed to fully satisfy the transport
requirements.
The general requirements of MPLS-TP are provided in MPLS-TP
Requirements [RFC 5654], and the architectural framework are defined
in MPLS-TP Framework [RFC 5921]. This document intent to provide the
use case studies and design considerations from practical point of
view based on Service Providers deployments plans and field
implementations.
The most common use cases for MPLS-TP include Mobile Backhaul, Metro
Ethernet access and aggregation, and Packet Optical Transport. MPLS-
TP data plane architecture, path protection mechanisms, and OAM
functionalities are used to support these deployment scenarios.
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MPLS-TP Use Cases Studies and Design Considerations October 2010
As part of MPLS family, MPLS-TP complements today's IP/MPLS
technologies; it closes the gaps in the traditional access and
aggregation transport to provide end-to-end solutions in a cost
efficient, reliable, and interoperable manner.
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) appear to be very attractive to many SPs. It streamlines
the operation, many help to reduce the overall complexity and
improve end-to-end convergence. It leverages the MPLS experience,
and enhances the ability to support revenue generating services.
The design considerations discussed in this document are generic.
While many design criteria are commonly apply to most of SPs, each
individual SP may place the importance of one aspect over another
depending on the existing operational environment, the applications
need to be supported, the design objective, and the expected
duration of the network to be in service for a particular design.
1.2. Contributing authors
Luyuan Fang, Cisco Systems
Nabil Bitar, Verizon
Raymond Zhang, BT
Masahiro DAIKOKU, KDDI
Jian Ping Zhang, China Telecom, Shanghai
Mach(Guoyi) Chen, Huawei Technologies
2. Terminologies
AIS Alarm Indication Signal
APS Automatic Protection Switching
ATM Asynchronous Transfer Mode
BFD Bidirectional Forwarding Detection
CC Continuity Check
CE Customer Edge device
CV Connectivity Verification
CM Configuration Management
DM Packet delay measurement
ECMP Equal Cost Multi-path
FM Fault Management
GAL Generic Alert Label
G-ACH Generic Associated Channel
GMPLS Generalized Multi-Protocol Label Switching
LB Loopback
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MPLS-TP Use Cases Studies and Design Considerations October 2010
LDP Label Distribution Protocol
LM Packet loss measurement
LSP Label Switched Path
LT Link trace
MEP Maintenance End Point
MIP Maintenance Intermediate Point
MP2MP Multi-Point to Multi-Point connections
MPLS Multi-Protocol Label Switching
MPLS-TP MPLS transport profile
OAM Operations, Administration, and Management
P2P Point to Multi-Point connections
P2MP Point to Point connections
PE Provider-Edge device
PHP Penultimate Hop Popping
PM Performance Management
PW Pseudowire
RDI Remote Defect Indication
RSVP-TE Resource Reservation Protocol with Traffic Engineering
Extensions
SLA Service Level Agreement
SNMP Simple Network Management Protocol
SONET Synchronous Optical Network
S-PE Switching Provider Edge
SRLG Shared Risk Link Group
TDM Time Division Multiplexing
TE Traffic Engineering
TTL Time-To-Live
T-PE Terminating Provider Edge
VPN Virtual Private Network
3. Overview of MPLS-TP base functions
The section provides a summary view of MPLS-TP technology,
especially in comparison to the base IP/MPLS technologies. For
complete requirements and architecture definitions, please refer to
[RFC 5654] and [RFC 5921].
3.1. MPLS-TP development principles
The principles for MPLS-TP development are: meeting transport
requirements; maintain transport characteristics; re-using the
existing MPLS technologies wherever possible to avoid duplicate the
effort; ensuring consistency and inter-operability of MPLS-TP and
IP/MPLS networks; developing new tools as necessary to fully meet
transport requirements.
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MPLS-TP Use Cases Studies and Design Considerations October 2010
MPLS-TP Technologies include four major areas: Data Plane, Control
Plane, OAM, and Survivability. The short summary is provided below.
3.2. Data Plane
MPLS-TP re-used MPLS and PW architecture; and MPLS forwarding
mechanism;
MPLS-TP extended the LSP support from unidirectional to both bi-
directional unidirectional support.
MPLS-TP defined PHP as optional, disallowed ECMP and MP2MP, only P2P
and P2MP are allowed.
3.3. Control Plane
MPLS-TP allowed two control plane options:
Static: Using NMS for static provisioning;
Dynamic Control Plane using GMPLS, OSPF-TE, RSVP-TE for full
automation
ACH concept in PW is extended to GACH for MPLS-TP LSP to support in-
band OAM.
Both Static and dynamic control plane options must allow control
plane and data plane separation.
3.4. OAM
OAM received most attention in MPLS-TP development; Many OAM
functions require protocol extensions or new development to meet
the transport requirements.
1) Continuity Check (CC), Continuity Verification (CV), and
Remote Integrity:
- Proactive CC and CV: Extended BFD
- On demand CC and CV: Extended LSP Ping
- Proactive Remote Integrity: Extended BFD
- On demand Remote Integrity: Extended LSP Ping
2) Fault Management:
- Fault Localization: Extended LSP Ping
- Alarm Suppression: create AIS
- Remote Defect Indication (RDI): Extended BFD
- Lock reporting: Create Lock Instruct
- Link defect Indication: Create LDI
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MPLS-TP Use Cases Studies and Design Considerations October 2010
- Static PW defect indication: Use Static PW status
Performance Management:
- Loss Management: Create MPLS-TP loss/delay measurement
- Delay Measurement: Create MPLS-TP loss/delay measurement
3.5. Survivability
- Deterministic path protection
- Switch over within 50ms
- 1:1, 1+1, 1:N protection
- Linear protection
- Ring protection
4. MPLS-TP Use Case Studies
4.1. Mobile Backhaul
Mobility is one of the fastest growing areas in communication world
wide. For some regions, the tremendous rapid mobile growth is fueled
with lack of existing land-line and cable infrastructure. For other
regions, the introduction of Smart phones quickly drove mobile data
traffic to become the primary mobile bandwidth consumer, some SPs
have already seen 85% of total mobile traffic are data traffic.
MPLS-TP has been viewed as a suitable technology for Mobile
backhaul.
4.1.1. 2G and 3G Mobile Backhaul Support
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
dominating mobile infrastructure today.
The connectivity for 2G/3G networks are Point to point. The logical
connections are hub-and-spoke. The physical construction of the
networks can be star topology or ring topology. In the Radio Access
Network (RAN), each mobile base station (BTS/Node B) is
communicating with one Radio Controller (BSC/RNC) only. These
connections are often statically set up.
Hierarchical Aggregation Architecture / Centralized Architecture are
often used for pre-aggregation and aggregation layers. Each
aggregation networks inter-connects with multiple access networks.
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MPLS-TP Use Cases Studies and Design Considerations October 2010
For example, single aggregation ring could aggregate traffic for 10
access rings with total 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 connection from base station to Radio Controller
can be set statically to mimic the operation today in many RAN
environments, in-band OAM and deterministic path protection would
support the fast failure detection and switch over to satisfy the
SLA agreement. Bidirectional LSP may help to simplify the
provisioning process. The deterministic nature of MPLS-TP LSP set up
can also help packet based synchronization to maintain predictable
performance regarding packet delay and jitters.
4.1.2. LTE Mobile Backhaul
One key difference between LTE and 2G/3G Mobile networks is that the
logical connection in LTE is mesh while 2G/3G is P2P star
connections.
In LTE, the base stations eNB/BTS can communicate with multiple
Network controllers (PSW/SGW or ASNGW), and each Radio element can
communicate with each other for signal exchange and traffic offload
to wireless or Wireline infrastructures.
IP/MPLS may have a great advantage in any-to-any connectivity
environment. The use of mature IP or L3VPN technologies is
particularly common in the design of SP's LTE deployment plan.
MPLS-TP can also bring advantages with the in-band OAM and path
protection mechanism. MPLS-TP dynamic control-plane with GMPLS
signaling may bring additional advantages in the mesh environment
for real time adaptivities, dynamic topology changes, and network
optimization.
Since MPLS-TP is part of the MPLS family. Many component already
shared by both IP/MPLS and MPLS-TP, the line can be further blurred
by sharing more common features. For example, it is desirable for
many SPs to introduce the in-band OAM developed for MPLS-TP back
into IP/MPLS networks as an enhanced OAM option. Today's MPLS PW can
also be set statically to be deterministic if preferred by the SPs
without going through full MPLS-TP deployment.
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MPLS-TP Use Cases Studies and Design Considerations October 2010
4.1.3. WiMAX Backhaul
WiMAX Mobile backhaul shares the similar characteristics as LTE,
with mesh connections rather than P2P, star logical connections.
4.2. Metro Access and Aggregation
Some SPs are building new Access and aggregation infrastructure,
while others plan to upgrade/replace of existing transport
infrastructure with new packet technologies such as MPLS-TP. The
later is of course more common than the former.
The access and aggregation networks today can be based on ATM, TDM,
MSTP, or Ethernet technologies as later development.
Some SPs announced their plans for replacing their ATM or TDM
aggregation networks with MPLS-TP technologies, because the ATM /
TDM aggregation networks are no longer suited to support the rapid
bandwidth growth, and they are expensive to maintain or may also be
and impossible expand due to End of Sale and End of Life legacy
equipments. The statistical muxing in MPLS-TP helps to achieve
higher efficiency comparing with the time division scheme in the
legacy technologies.
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) appear to be very attractive to many SPs. It streamlines
the operation, many help to reduce the overall complexity and
improve end-to-end convergence. It leverages the MPLS experience,
and enhances the ability to support revenue generating services.
The current requirements from the SPs for ATM/TDM aggregation
replacement often include maintaining the current operational model,
with the similar user experience in NMS, supports current access
network (e.g. Ethernet, ADSL, ATM, STM, etc.), support the
connections with the core networks, support the same operational
feasibility even after migrating to MPLS-TP from ATM/TDM and
services (OCN, IP-VPN, E-VLAN, Dedicated line, etc.). MPLS-TP
currently defined in IETF are meeting these requirements to support
a smooth transition.
The green field network deployment is targeting using the state of
art technology to build most stable, scalable, high quality, high
efficiency networks to last for the next many years. IP/MPLS and
MPLS-TP are both good choices, depending on the operational model.
4.3. Packet Optical Transport
(to be added)
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MPLS-TP Use Cases Studies and Design Considerations October 2010
5. Network Design Considerations
5.1. IP/MPLS vs. MPLS-TP
Questions we often hear: I have just built a new IP/MPLS network to
support multi-services, including L2/L3 VPNs, Internet service,
IPTV, etc. Now there is new MPLS-TP development in IETF. Do I need
to move onto MPLS-TP technology to state current with technologies?
The answer is no generally speaking. MPLS-TP is developed to meet
the needs of traditional transport moving towards packet. It is
geared to support the transport behavior coming with the long
history. IP/MPLS and MPLS-TP both are state of art technologies.
IP/MPLS support both transport (e.g. PW, RSVP-TE, etc.) and services
(e.g L2/L3 VPNs, IPTV, Mobile RAN, etc.), MPLS-TP provides transport
only. The new enhanced OAM features built in MPLS-TP should be share
in both flavors through future implementation.
Another question: I need to evolve my ATM/TDM/SONET/SDH networks
into new packet technologies, but my operational force is largely
legacy transport, not familiar with new data technologies, and I
want to maintain the same operational model for the time being, what
should I do? The answer would be: MPLS-TP may be the best choice
today for the transition.
A few important factors need to be considered for IP/MPLS or MPLS-TP
include:
- Technology maturity (IP/MPLS is much more mature with 12 years
development)
- Operation experience (Work force experience, Union agreement, how
easy to transition to a new technology? how much does it cost?)
- Needs for Multi-service support on the same node (MPLS-TP provide
transport only, does not replace many functions of IP/MPLS)
- LTE, IPTV/Video distribution considerations (which path is the
most viable for reaching the end goal with minimal cost? but it also
meet the need of today's support)
5.2. Standards compliance
It is generally recognized by SPs that standards compliance are
important for driving the cost down and product maturity up, multi-
vendor interoperability, also important to meet the expectation of
the business customers of SP's.
MPLS-TP is a joint work between IETF and ITU-T. In April 2008, IETF
and ITU-T jointly agreed to terminate T-MPLS and progress MPLS-TP as
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MPLS-TP Use Cases Studies and Design Considerations October 2010
joint work [RFC 5317]. The transport requirements would be provided
by ITU-T, the protocols would be developed in IETF.
T-MPLS is not MPLS-TP. T-MPLS solution would not inter-op with
IP/MPLS, it would not be compatible with MPLS-TP defined in IETF.
5.3. End-to-end MPLS OAM consistency
In the case Service Providers deploy end-to-end MPLS solution with
the combination of dynamic IP/MPLS and static or dynamic MPLS-TP
cross core, service edge, and aggregation/access networks, end-to-
end MPLS OAM consistency becomes an essential requirements from many
Service Provider. The end-to-end MPLS OAM can only be achieved
through implementation of IETF MPLS-TP OAM definitions.
5.4. Delay and delay variation
Background/motivation: Telecommunication Carriers plan to replace
the aging TDM Services (e.g. legacy VPN services) provided by Legacy
TDM technologies/equipments to new VPN services provided by MPLS-TP
technologies/equipments with minimal cost. The Carriers cannot allow
any degradation of service quality, service operation Level, and
service availability when migrating out of Legacy TDM
technologies/equipments to MPLS-TP transport. The requirements from
the customers of these carriers are the same before and after the
migration.
5.4.1. Network Delay
From our recent observation, more and more Ethernet VPN customers
becoming very sensitive to the network delay issues, especially the
financial customers. Many of those customers has upgraded their
systems in their Data Centers, e.g., their accounting systems. Some
of the customers built the special tuned up networks, i.e. Fiber
channel networks, in their Data Centers, this tripped more strict
delay requirements to the carriers.
There are three types of network delay:
1. Absolute Delay Time
Absolute Delay Time here is the network delay within SLA contract.
It means the customers have already accepted the value of the
Absolute Delay Time as part of the contract before the Private Line
Service is provisioned.
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MPLS-TP Use Cases Studies and Design Considerations October 2010
2. Variation of Absolute Delay Time (without network configuration
changes).
The variation under discussion here is mainly induced by the
buffering in network elements.
Although there is no description of Variation of Absolute Delay Time
on the contract, this has no practical impact on the customers who
contract for the highest quality of services available. The
bandwidth is guaranteed for those customers' traffic.
3. Relative Delay Time
Relative Delay Time is the difference of the Absolute Delay Time
between using working and protect path.
Ideally, Carriers would prefer the Relative Delay Time to be zero,
for the following technical reasons and network operation
feasibility concerns.
The following are the three technical reasons:
Legacy throughput issue
In the case that Relative Delay Time is increased between FC
networks or TCP networks, the effective throughput is degraded. The
effective throughput, though it may be recovered after revert back
to the original working path in revertive mode.
On the other hand, in that case that Relative Delay Time is
decreased between FC networks or TCP networks, buffering over flow
may occur at receiving end due to receiving large number of busty
packets. As a consequence, effective throughput is degraded as
well. Moreover, if packet reordering is occurred due to RTT
decrease, unnecessary packet resending is induced and effective
throughput is also further degraded. Therefore, management of
Relative Delay Time is preferred, although this is known as the
legacy TCP throughput issue.
Locating Network Acceralators at CE
In order to improve effective throughput between customer's FC
networks over Ethernet private line service, some customer put "WAN
Accelerator" to increase throughput value. For example, some WAN
Accelerators at receiving side may automatically send back "R_RDY"
in order to avoid decreasing a number of BBcredit at sending side,
and the other WAN Accelerators at sending side may have huge number
of initial BB credit.
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MPLS-TP Use Cases Studies and Design Considerations October 2010
When customer tunes up their CE by locating WAN Accelerator, for
example, when Relative Delay Time is changes, there is a possibility
that effective throughput is degraded. This is because a lot of
packet destruction may be occurred due to loss of synchronization,
when change of Relative delay time induces packet reordering. And,
it is difficult to re-tune up their CE network element automatically
when Relative Delay Time is changed, because only less than 50 ms
network down detected at CE.
Depending on the tuning up method, since Relative Delay Time affects
effective throughput between customer's FC networks, management of
Relative Delay Time is preferred.
c) Use of synchronized replication system
Some strict customers, e.g. financial customers, implement
"synchronized replication system" for all data back-up and load
sharing. Due to synchronized replication system, next data
processing is conducted only after finishing the data saving to both
primary and replication DC storage. And some tuning function could
be applied at Server Network to increase throughput to the
replication DC and Client Network. Since Relative Delay Time affects
effective throughput, management of Relative Delay Time is
preferred.
The following are the network operational feasibility issues.
Some strict customers, e.g., financial customer, continuously
checked the private line connectivity and absolute delay time at
CEs. When the absolute delay time is changed, that is Relative
delay time is increased or decreased, the customer would complain.
From network operational point of view, carrier want to minimize the
number of customers complains, MPLS-TP LSP provisioning with zero
Relative delay time is preferred and management of Relative Delay
Time is preferred.
Obviously, when the Relative Delay Time is increased, the customer
would complain about the longer delay. When the Relative Delay Time
is decreased, the customer expects to keep the lesser Absolute Delay
Time condition and would complain why Carrier did not provide the
best solution in the first place. Therefore, MPLS-TP LSP
provisioning with zero Relative Delay Time is preferred and
management of Relative Delay Time is preferred.
More discussion will be added on how to manage the Relative delay
time.
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MPLS-TP Use Cases Studies and Design Considerations October 2010
5.5. General network design considerations
- Migration considerations
- Resilency
- Scalability
- Performance
6. MPLS-TP Deployment Consideration
6.1. Network Modes Selection
When considering deployment of MPLS-TP in the network, possibly
couple of questions will come into mind, for example, where should
the MPLS-TP be deployed? (e.g., access, aggregation or core
network?) Should IP/MPLS be deployed with MPLS-TP simultaneously? If
MPLS-TP and IP/MPLS is deployed in the same network, what is the
relationship between MPLS-TP and IP/MPLS (e.g., peer or overlay?)
and where is the demarcation between MPLS-TP domain and IP/MPLS
domain? The results for these questions depend on the real
requirements on how MPLS-TP and IP/MPLS are used to provide
services. For different services, there could be different choice.
According to the combination of MPLS-TP and IP/MPLS, here are some
typical network modes:
Pure MPLS-TP as the transport connectivity (E2E MPLS-TP), this
situation more happens when the network is a totally new constructed
network. For example, a new constructed packet transport network for
Mobile Backhaul, or migration from ATM/TDM transport network to
packet based transport network.
Pure IP/MPLS as transport connectivity (E2E IP/MPLS), this is the
current practice for many deployed networks.
MPLS-TP combines with IP/MPLS as the transport connectivity (Hybrid
mode)
Peer mode, some domains adopt MPLS-TP as the transport connectivity;
other domains adopt IP/MPLS as the transport connectivity. MPLS-TP
domains and IP/MPLS domains are interconnected to provide transport
connectivity. Considering there are a lot of IP/MPLS deployments in
the field, this mode may be the normal practice in the early stage
of MPLS-TP deployment.
Overlay mode
b-1: MPLS-TP as client of IP/MPLS, this is for the case where MPLS-
TP domains are distributed and IP/MPLS do-main/network is used for
the connection of the distributed MPLS-TP domains. For examples,
there are some service providers who have no their own Backhaul
network, they have to rent the Backhaul network that is IP/MPLS
based from other service providers.
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MPLS-TP Use Cases Studies and Design Considerations October 2010
b-2: IP/MPLS as client of MPLS-TP, this is for the case where
transport network below the IP/MPLS network is a MPLS-TP based
network, the MPLS-TP network provides transport connectivity for the
IP/MPLS routers, the usage is analogous as today's ATM/TDM/SDH based
transport network that are used for providing connectivity for
IP/MPLS routers.
6.2. Provisioning Modes Selection
As stated in MPLS-TP requirements [RFC5654], MPLS-TP network MUST be
possible to work without using Control Plane. And this does not mean
that MPLS-TP network has no control plane. Instead, operators could
deploy their MPLS-TP with static provisioning (e.g., CLI, NMS etc.),
dynamic control plane signaling (e.g., OSPF-TE/ISIS-TE, GMPLS, LDP,
RSVP-TE etc.), or combination of static and dynamic provisioning
(Hybrid mode). Each mode has its own pros and cons and how to
determine the right mode for a specific network mainly depends on
the operators' preference. For the operators who are used to operate
traditional transport network and familiar with the Transport-
Centric operational model (e.g., NMS configuration without control
plane) may prefer static provisioning mode. The dynamic provisioning
mode is more suitable for the operators who are familiar with the
operation and maintenance of IP/MPLS network where a fully dynamic
control plane is used. The hybrid mode may be used when parts of the
network are provisioned with static way and the other parts are
controlled by dynamic signaling. For example, for big SP, the
network is operated and maintained by several different departments
who prefer to different modes, thus they could adopt this hybrid
mode to support both static and dynamic modes hence to satisfy
different requirements. Another example is that static provisioning
mode is suitable for some parts of the network and dynamic
provisioning mode is suitable for other parts of the networks (e.g.,
static for access network, dynamic for metro aggregate and core
network).
Note: This draft is work in progress, more would be filled in the
following revision.
7. Security Considerations
Reference to [RFC 5920]. More will be added.
8. IANA Considerations
This document contains no new IANA considerations.
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MPLS-TP Use Cases Studies and Design Considerations October 2010
9. Normative References
[RFC 5317]: Joint Working Team (JWT) Report on MPLS Architectural
Considerations for a Transport Profile, Feb. 2009.
[RFC 5654], Niven-Jenkins, B., et al, "MPLS-TP Requirements," RFC
5654, September 2009.
(More to be added)
10.Informative References
[RFC 5921] Bocci, M., ED., Bryant, S., ED., et al., Frost, D. ED.,
Levrau, L., Berger., L., "A Framework for MPLS in Transport," July
2010.
[RFC 5920] L. Fang, ED., et al, "Security Framework for MPLS and
GMPLS Networks, " July 2010.
(More to be added)
11.Author's Addresses
Luyuan Fang
Cisco Systems, Inc.
111 Wood Ave. South
Iselin, NJ 08830
USA
Email: lufang@cisco.com
Dan Frost
Cisco Systems, Inc.
Email: danfrost@cisco.com
Nabil Bitar
Verizon
40 Sylvan Road
Waltham, MA 02145
USA
Email: nabil.bitar@verizon.com
Raymond Zhang
British Telecom
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MPLS-TP Use Cases Studies and Design Considerations October 2010
BT Center
81 Newgate Street
London, EC1A 7AJ
United Kingdom
Email: raymond.zhang@bt.com
Masahiro DAIKOKU
KDDI corporation
3-11-11.Iidabashi, Chiyodaku, Tokyo
Japan
Email: ms-daikoku@kddi.com
Jian Ping Zhang
China Telecom, Shanghai
Room 3402, 211 Shi Ji Da Dao
Pu Dong District, Shanghai
China
Email: zhangjp@shtel.com.cn
Lai Wang
Telenor
Telenor Norway
Office Snaroyveien
1331 Fornedbu
Email: Lai.wang@telenor.com
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
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