Tata Communications is taking a technology route less-traveled (so far) by transitioning away from its Layer 1 SONET/SDH network and deploying Ethernet Provider Backbone Bridging (PBB) in 24 nodes around the world to future-proof its global network. To cut out a network layer, the India-based provider chose PBB over a hybrid IP/Ethernet solution to scale its core network as Carrier Ethernet use grows, the company said.
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We realized that if we were going to keep growing at the current pace, our technology would reach a limit where our costs increased more than our pricing.
"About two years ago, we realized that if we were going to keep growing at the current pace, our technology would reach a limit where our costs increased more than our pricing," said John Hoffman, head of Ethernet product management for Tata Communications. At that point, Tata decided it would bypass Layer 1 and gain access to physical transport from Layer 2.
While PBB offers good scalability, operating expense (OpEx) and incremental bandwidth options, it doesn't do everything SONET can. Originally created by Nortel, PBB is an IEEE-approved protocol (802.1ah) that routes traffic over a provider's network without losing a customer's individual virtual LAN (VLAN).
"Several competitors have responses in place for all the benefits Tata is aiming to present to clients," said Current Analysis Senior Analyst Joel Stradling. "But overall, Tata is bringing a future-proof message to market and is currently a leading carrier in terms of Ethernet virtual private LAN service (VPLS) reach. This PBB upgrade is certainly giving the competition something to think about."
As the first global provider to go the PBB route with its core network, Tata assessed every vendor option and chose Cisco's ASR 9000 Carrier Ethernet router. "It achieved everything we wanted to achieve and it has a great roadmap," Hoffman said. "One of the concerns with any technology investment is that it continues to pay in the long run because you can't afford to redo your network every three years."
PBB advantages for wholesale customers leaving SONET behind
Tata believes one of the biggest advantages for its wholesale service provider customers -- 30% of its customer base -- will be the ability to buy bandwidth in 50 Megabits per second, Hoffman said. It will also expand its product set to include burstable bandwidth to scale from 1,000 to 10,000 Meg in 500 Meg increments.
Another concern is the ability to protect against network failures. Tata's PBB network will have nodal diversity to take the place of SONET's self-healing capabilities, first in Europe, the east and west coasts of the U.S., Japan and Singapore, which account for 75% of Tata's traffic. The first 24 nodes replace about half of Tata's equipment; the rest will be phased in as new boxes are needed.
"For some carriers, nodal diversity means having equipment two racks away," Hoffman said. "For us, traffic would switch to the other node, which is in another city."
PBB's "deterministic protection," where a fixed path can be configured to handle traffic in case of congestion or failure on a given circuit, improves resilience and gives Tata a better OPEX model for management, Stradling said.
PBB addresses limited MAC address issues for point-to-multipoint
Ethernet traffic is expected to shifts from today's predominantly point-to-point connections to point-to-multipoint, which could make up as much as 40% of service providers' revenues within five years, Hoffman said. To scale up for the change, PBB doesn't use customers' Media Access Control (MAC) addresses addresses for service routing, like other types of Ethernet networks do.
When forwarding frames on a multipoint network, PBB assigns a unique identifier called a B-MAC to each service, which decreases the amount of information that has to be stored in MAC address lookup databases. This also helps protect customers from distributed denial of service (DDOS) attacks, which are usually launched against specific customer MAC addresses, Hoffman said.
MAC address scaling, which has a current limit of 4,094 endpoints, is expanded to 16.7 million individual VLAN services with PBB, Stradling said.
"Every piece of network equipment limits how many MAC addresses it can handle in a MAC look-up database, and every technology except PBB uses the customer's MAC address to forward the frame," Hoffman said. "Everyone should care about that because as multipoint Ethernet traffic grows because the number of MAC addresses you would be managing would be huge."
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