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MPLS-TP: Winning the Protocol Wars at MPLS & Ethernet World Congress 2010

At the recent MPLS conference in Paris, MPLS-TP was a hot topic, what is the reason behind the success of MPLS-TP and why has PBB-TE proven so far to be unsuccessful? Also in this blog I explore whether there is a place for PBB in the network?
PBB-TE offered to give network operators a scalable, statically configured traffic engineered path through the network, and by complimenting this with OAM features such as Connectivity Fault Management (CFM/IEEE 802.1ag) the plan was that a carrier class transport protocol would be unleashed based on Ethernet. PBB-TE was standardised in 2009 as IEEE 802.1Qay.

MPLS-TP (Transport Profile of MPLS) on the other hand is a relative latecomer to the party, but has quickly gained traction with many in the industry. The origins of MPLS-TP can be found by looking at the now mothballed T-MPLS work started by the ITU-T. This Transport MPLS solution aimed to provide a scalable, statically provisioned, traffic engineered path through the network, and hoped to add a new set of OAM features. However, the ITU-T proposals were fiercely argued by the IETF (responsible for the MPLS framework) as a misguided activity partly due to overloaded use of the Ethertype (used to mark the presence of T-MPLS in the Ethernet frame) causing a conflict between MPLS and T-MPLS when running on the same network.

The on-going need for a transport protocol aligned to the MPLS user base caused parties involved in IETF and ITU-T to get together and design a workable solution that satisfied both the needs of the operator and which is based on a proven carrier class technology. MPLS is that carrier class technology, having being deployed in most large networks around the world, and thus the new protocol, MPLS-TP was created.

So what is MPLS-TP?

The message from the chair of the IETF MPLS Working Group, Loa Anderson is that MPLS-TP is part of the MPLS toolbox. MPLS with additions such as:

  • Transport like Operation
    - Static provisioning via NMS as a default
    - Dynamic provisioning optional via control plane respectively
    - Traffic Engineering rules
  • Transport like OAM using in-band OAM channels
    - Support performance monitoring for SLA verification
    - Alarms and AIS
  • Transport-like Resilience
    - Sub 50ms protection
    - Linear protection
    - Ring protection

The data/forwarding plane is essentially the same as the MPLS forwarding operation, with OAM signalling being achieved by a reserved MPLS label called the GAL – Generic Alert Label (value 13) and subsequent associated OAM message embedded within the Associated Channel header (G-ACH) within the payload. This label is exposed at the MPLS-TP Path end-points (MEPs) when the outer label is popped, or at intermediate nodes (MIPs) by appropriate setting of the TTL fields in the outer label. This OAM signalling (based on the principles of PW signalling)is needed to replace standard MPLS OAM functions such as LSP Ping and BFD since there may be no control plane or IP layer in operation.

MPLS-TP is said to be 75% standardised, with the ITU-T due to consent on the recommendations in June.

In my view PBB-TE stands still while MPLS-TP moves forward due to the small install base and lack of industry approved tools for operating in loop topologies, whereas MPLS is at an advantage with most operators being already over the learning curve of this technology since MPLS is already extensively deployed in carrier networks.

At the MPLS & Ethernet World Congress, Provider Backbone Bridging (PBB, IEEE 802.1ah aka MACinMAC) received a fair amount of attention. Note that this is different from PBB-TE in that it continues to supports bridging functions normally supported by Ethernet i.e. MAC address learning, flooding of unknown MAC destination addresses, flooding of broadcast etc, and therefore it is complimentary to the Layer 2 aspects of L2VPN technology i.e. VPLS and H-VPLS.

PBB allows VPLS to be scaled by encapsulating many customer MAC addresses into a path transported by one backbone MAC address (MAC scaling) and also reduces the number of pseudowire tunnels required within the MPLS core (PW reduction). PBB+VPLS was mentioned by Verizon as a key technology and by several vendors as a method of scaling multipoint to multipoint Inter Cloud services.

So MPLS-TP is winning the debate for transport, but PBB will surely have a place in the network.  Once PBB matures and carriers gain operational experience, one might see PBB-TE rising back up the ‘hype curve’ and causing round 2 of the protocol wars.

  • http://irkos.org Irek Szcześniak

    Hi,

    Thanks for your interesting post. You noted that MPLS-TP is winning the battle over PBB-TE. Your post is nearly two years old now, and I wonder whether much has changed. Is there more interest in PBB-TE or MPLS-TP? Companies which invested in Ethernet, like Ciena, bet on PBB-TE, and companies which invested in MPLS, like Cisco, bet on MPLS-TP. Are there some other major reasons to go for MPLS-TP or PBB-TE?

    Thanks,
    Irek

    • http://www.linkedin.com/in/vishalsharma Vishal Sharma

      Hi Irek,

      First a couple of thoughts:

      i) PBB-TE was really a solution more for the metro/core networks, while MPLS-TP is more a solution for the access/metro network segments. (Now one could certainly use MPLS-TP for the core too, but given that, at least as of Jan. 2012, the provisioning for MPLS-TP is largely manual (with proposals for a GMPLS-based control plane, eventually)), it may not (in it’s current form) be very useful for the core or even the metro-core, if you will).

      Now, PBB-TE is manually provisioned too (at least in the intial incarnation) with PLSB (provider link-state bridging) as the proposed dynamic routing technique.

      ii) Second, MPLS-TP is a way of extending MPLS-like functionality with a transport-like feel to the access links, useful in applications like mobile backhaul (where it would compete with PBB, more than with PBB-TE).

      iii) Third, PBB-TE is obviously confined to Ethernet-only networks (of course, it’s payload, like that of MPLS-TP, could be anything).

      So, the decision to go with MPLS-TP or PBB (for the access) would depend on whether the operator in question is keen on having an Ethernet-based metro/access network, or is looking at an IP/MPLS network that they wish to extend to the metro/access regions.
      It would, of course, also, as you’ve observed, be driven by the vendor wars. If a majority of vendors line up with one technology (MPLS-TP), there will definitely (eventually) be more adoption of it (especially given today’s trends, where in many parts of the world, the vendors’ professional services or engineering services have significant input on the provider’s architecture).

      The decision to go with MPLS-TP or PBB-TE (actually this would be more between IP/MPLS core and PBB-TE core) would depend on whether the operator has or wishes to have an Ethernet-only core (or metro-core, since the real core in many cases may be IP or IP/MPLS).
      My undertanding is that, despite the ostensible beating that PBB-TE took, there have been operators who have deployed that (or some similar version) in their networks.

      Best,
      -Vishal

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  • Vic Nowoslawski

    Does your company support PBB-TE or MPLS-TP?
    Which one are you looking at supporting? It sounds like you are in the MPLS-TP camp.

  • Anthony Magee

    Hi Vic,

    First, let me thank you for taking the time to submit a question on my blog entry.

    ADVA Optical Networking are currently tracking both of these within our sector.  Our devices which could be used for this type of transport engineered solution are flexible in design approach and are not tied to one technology or the other.

    I personally believe that MPLS-TP will be the dominant requirement in the short term.

    Is this how you view things?

    Regards,

    Anthony

  • Alexandre Almeida

    Hi Anthony,

    what is your vision regarding SyncEtehrnet and 1588V2 synchronization schemes for MPLS-TP networks?

  • Frederick

    It looks like they were able to avoid the issue that others were having regarding pst repair. It’s always good thing when you can work your way around issues like that. Interesting entry.