Synchronization Remains The Biggest Headache For Ethernet Backhaul

The mobile backhaul equipment market grew 10.3% in 2010 compared to the previous year, reaching a value of $6.84bn worldwide, according to Infonetics. This growth was driven by “almost universal” adoption of IP/Ethernet as data traffic rises. However, challenges remain, notably in network synchronization, and as in the RAN, carriers are looking for new ways to design their backhaul networks.

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• In 2010, the survey says, 89% of money spent on mobile backhaul equipment was for IP/Ethernet, with the fastest growth seen in packet microwave and in Ethernet cell site routers and gateways. Ericsson increased its lead in the former space in 2010, while in the second half the cell site routers/gateways segment was dominated by Alcatel-Lucent, Tellabs, Cisco and Huawei, which share over 75% of the market.
• The primary reason for operators to hold onto their old TDM circuits is the challenge of network synchronization in Ethernet, so it is common for them to have hybrid systems, carrying voice over traditional E1 links and data over Ethernet. British Telecom told the recent Ethernet Europe conference that, despite the cost, the carrier still operates its TDM network along with Ethernet connections and will have to implement both new synchronization standards before it can change that.
• The standards are Synchronous Ethernet and IEEE 1588v2, but there are risks associated with both at this early stage. SyncE is becoming established and highly trusted, but there are performance question marks over 1588v2, even though, in theory, it is simpler. Michael Ritter, head of technical marketing at optical networking firm ADVA, told the session: “There has to be a more common and versatile approach. There will be much more complex backhaul architectures be- cause of all this."
• ADVA itself is one of the companies looking at new ways to do backhaul and addressing the synchronization issue. It claims it is creating a new product category – the Carrier Ethernet edge gateway. This targets backhaul as well as low latency applications. The firm’s first product for this space is the FSP 150 EG-X, which aggregates traffic from multiple network interface devices (NIDs) and feeds it to a port on a carrier’s IP-MPLS network. It differs from other products with this functionality because it also has “gateway functionality” - capabilities that carriers need to manage Ethernet traffic.
• The company says these are stripped out before an Ethernet packet hits the core network and are put back on when the packet reaches a gateway device. Such capabilities include multilayer priority mapping, which ensures that packets are not dropped, unlike a traditional router when used for Ethernet aggregation. ADVA says it had expected the router makers to add this function to their products, but when they did not, it targeted the gap itself, with a separate offering.
• It also hopes it will differentiate itself by attacking synchronization and timing. It says carriers are keen to return to getting timing from the network rather than GPS, and the new gateway supports the 1588v2 standard in every one of its 140 Gig Ethernet ports, and each of them can also be a Synch-E master or slave clock. Most vendors only have one port operating as a clock manager, which can cause problems if several operators use the same tower.
• “For a carrier that wants to be a backhaul vendor, it can put [wireless operators] on its fiber and say, “there’s an Ethernet virtual circuit that keeps you separate from other traffic and you don’t have to share the timing domain‟, said technical marketing director Jim Theodoras. He also says the product can resolve incompatibility problems with using both Synch-E and 1588. “The two fight each other sometimes and we have the ability to mediate between them if they report two different clock timings,” he told ConnectedPlanet. “We resolve it on a port-to-port basis.”