The document discusses the evolution of MPLS-TP (Transport MPLS), which emerged from the need for high-bandwidth packet-based services over existing MPLS frameworks. It highlights how MPLS-TP is designed to offer reliable transport network capabilities while minimizing costs, addressing control plane issues and supporting various applications like mobile backhaul. References to key documents and standards related to MPLS-TP are also provided for further exploration.

1. 2012
www.mplsvpn.info
Shivlu Jain
[MPLS-TP]

2. History
Most of the operators are using circuit switched technology as transport network. But most of the
services are packet based services, so why not to use packet based networks to offer high bandwidth
packet based services. The need of high bandwidth hungry application demands to upgrade the
infrastructure. But the same time operators want to reduce their per bit infrastructure cost with
minimal capex and opex involved. MPLS had already been deployed widely to offer packet based
services, then why not to use MPLS as transport too. This was the reason to add T-MPLS (Transport
MPLS) for transport services too. T-MPLS was subset of MPLS. T-MPLS discussion was initially started by
ITU-T in 2006. At that time, ITU shown their interest to use the existing MPLS framework defined by IETF
and incorporate all the MPLS functionalities in T-MPLS.
Figure 1
After some time, the T-MPLS reached the stage where in some vendors started building their product by
adding T-MPLS capabilities. But at the same time, IETF was also working on PWE3 to emulate any kind of
access service over packet switched network over MPLS. On April 18, 2008 ITU and IETF had formed a
joint working team to address all the issues and ceased the T-MPLS implementation. Thereafter, T-MPLS
was changed to MPLS-TP as shown in figure 1.
Joint working report was submitted in RFC 5317 (http://www.ietf.org/rfc/rfc5317.pdf)
Requirement of Transport Network
Transport network must be enough reliable to handle any kind of customer traffic to any scale. That
time only Ethernet was the one which could be foreseen as futuristic technology because no other
Shivlu Jain www.mplsvpn.info

3. technology can scale as much as Ethernet can. The other advantage of using Ethernet was to use its
statmuxing which would actually lower down the cost per bit of operator.
Figure 2
What is MPLS-TP?
MPLS-TP is subset of MPLS. It uses the same data plane as used by MPLS (Defined in RFC 3031 and RFC
3032). MPLS-TP has four major areas:-
1. Data Plane
2. Control Plane
3. O&M
4. Survivability
MPLS-TP has no control plane, the reason for this was that the recovery. If the dynamic control plane is
used, in that case the convergence would depend on the dynamic protocol and providers cannot
leverage the <50 ms failover time in that case. It uses the same QoS diffserv model except uniform
model as used in MPLS.
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4. Mapping of MPLS-TP
Figure 3
Use Cases of MPLS-TP
Service providers are using Ethernet in the core with MPLS but still most of the access networks are still
using legacy technologies like SDH/ATM and Frame-Relay. Below is the list of the area where MPLS-TP
can be used:-
1. Metro Access and Aggregation
2. Packet Optical Transport Network
3. 2G and 3G mobile backhaul
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5. MPLS-TP
MSC
Primary Path BSC
BTS MPLS-TP MPLS-TP
MPLS-TP PSTN
1 or 10 G
N X E1
Ring N X E1
Secondary
Path
ATM
Ethernet Ethernet
nodeB Vlan 100 MPLS/
MPLS-TP Vlan 100
RNC INTERNET
Static TP
SGSN GGSN
LSP
Static
PWE3
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4. LTE Mobile Backhaul
5. Wimax Backhaul
References
MPLS TP Requirements http://tools.ietf.org/html/rfc5654
MPLS TP Use Cases http://tools.ietf.org/id/draft-fang-mpls-tp-use-
cases-and-design-04.txt
MPLS TP Data Plane http://tools.ietf.org/html/rfc5921#ref-DATA-
PLANE
Avoiding ECMP in MPLS http://tools.ietf.org/html/rfc4928
JWT Report http://www.ietf.org/rfc/rfc5317.pdf
MPLS-TP Framework https://tools.ietf.org/html/rfc5921
Inter working between IP-MPLS and MPLS-TP http://tools.ietf.org/html/draft-martinotti-mpls-
tp-interworking-01
Requirements of OAM in MPLS-TP http://tools.ietf.org/html/rfc5860
Shivlu Jain www.mplsvpn.info