Ethernet tunnel technologies such as Provider Backbone Transport (PBT) and Transport MPLS (T-MPLS) are generating a great deal of interest. Tunnel technologies aim to enable “connection-oriented” Ethernet transport with high levels of reliability, manageability and scalability.
Note that PBT has been given a new name by the IEEE in the project authorization, and we’ll use the new name: Provider Backbone Bridging – Traffic Engineering.
|
|
PBB-TE |
T-MPLS |
|
What is its origin? |
A subset of IEEE Provider Backbone Bridging (802.1ah). |
A derivative of IETF MPLS. |
|
What does it do? |
Turns Ethernet connectionless networking into a provisioned connection-oriented transport network primarily for point-to-point Ethernet virtual connections. |
Enables a connection-oriented packet transport capability primarily for point-to-point connections for a number of link layer networks (e.g. Ethernet, Packet over SONET/SDH). |
|
How is it implemented? |
Uses B-VID tags and destination B-MAC addresses to provide the connection-oriented forwarding capability. Disables the Ethernet LAN features such as learning, flooding/broadcasting and spanning tree protocol. Initially a centralized provisioning methodology is used for configuring PBB-TE path connections. |
Uses a 20-bit T-MPLS label that is added to the incoming traffic. The hop-by-hop T-MPLS header is used to provide the connection-oriented capability.
|
|
What are the advantages? |
PBB-TE is based on native Ethernet technology and therefore has the potential to leverage its simplicity and lower cost. Also, PBB-TE is based on a global address (e.g. includes source address), which is beneficial in OAM capabilities. |
Further ahead than PBB-TE in the standardization process. Supports mapping of multiple services such as ATM, Frame Relay and Ethernet. |
|
What are the disadvantages? |
The standardization process is currently in its infancy.
|
Adds additional header information and processing that may be extra overhead in some applications. |
|
Is it standardized? |
An initial IEEE project authorization has been submitted for PBB-TE, as a subset of the IEEE 802.1ah standard. PBB-TE is looking to leverage the IEEE OAM standardization work being undertaken as part of the IEEE 802.1ag (ITU Y1731) standard currently being progressed through the IEEE. |
T-MPLS is a work-in-progress at the ITU-T (Study Group 15). T-MPLS OAM is looking to use the ITU Y.1711 standard currently under discussion, while also looking to leverage the IEEE OAM standardization work being undertaken as part of the IEEE 802.1ag (Y1731) standard currently being progressed through the IEEE for Ethernet. |
|
Where does it fit best? |
If the carrier has a predominance of Ethernet, particularly if Ethernet is the link layer of choice in the access and metro, then it may be preferable to use PBB-TE with WDM/OTN. |
Today, many carriers have invested heavily in IP/MPLS and Packet over SONET/SDH in the core of their networks, therefore T-MPLS may be the best fit for the core of the network. |
|
Meriton’s Perspective |
Meriton’s initial customers have requested PBB-TE. |
Meriton’s Carrier Ethernet Transport (CET) solution will support T-MPLS and this will be delivered as part of the Meriton CET solution roadmap. |
PBT Resources
Wikipedia Entry
http://en.wikipedia.org/wiki/Provider_Backbone_Transport
TPACK White Paper
http://www.tpack.com/solutions
Light Reading Webinar “Ethernet’s Core Question: The Case for PBT”
http://www.lightreading.com/webinar_archive.asp?doc_id=28135
T-MPLS Resources
TPACK White Paper
http://www.tpack.com/solutions
T-MPLS Forum