Law Firm Relies on Traffic Shaping for Wan Performance.

A project to consolidate servers in a central data centre highlighted the need for international law firm Reed Smith to use traffic-shaping technology to ensure that its most important applications perform well on its now-critical WAN.

So far Reed Smith has used Packeteer PacketShapers to prioritise key flows, limit or block unnecessary traffic and adjust the size of its WAN links to make the network as cost-effective as possible, says Frank Hervert, senior manager of network and messaging services for the firm.

He doesn't have a quantified return on investment, but the Packeteer appliances enable him to cost-justify increases or decreases in bandwidth, so the firm doesn't pay for bandwidth it doesn't use. "Over a six-month term that will easily save me money beyond the cost of the PacketShaper," he says.

The equipment also provides monitoring and records that enable Reed Smith to double-check carrier services and ensure that service providers meet service-level agreements and configure the network in accordance with its design, he says.

The Pittsburgh-based law firm has 15 offices in the US and six offices overseas. Each used to have its own Internet access and servers, but for the past two years, the firm has been consolidating its servers and Internet access at a leased secure data centre.

The centralisation is about 60 percent complete for the US offices, Hervert says. In June, the firm plans to switch its foreign offices to a new European data centre based on the same model.

Centralised apps

The US data centre contains 180 Citrix servers that host the law firm's key applications, including common office applications such as Word, Excel, PowerPoint and e-mail. "All of that processing is centralised out of one data centre," he says. "That affords us LAN-like access anywhere."

The company bases its fully meshed primary WAN on MPLS services supplied by AT&T. That network is backed up by an Ethernet WAN from Yipes. Connections into the data centre from the carriers are separate OC-3 fibre links.

With the MPLS network, each large office is connected to the service with DS-3 lines that have committed access rates (CAR) less than the 45Mbit/s capacity of the connections. But traffic on these pipes is allowed to burst up to the full bandwidth. Smaller offices are connected via T-1s or multiple T-1s, he says. This primary network is used for critical business applications.

The backup Ethernet network also has DS-3 backhauls to a Yipes Layer 2 Ethernet network. Some sites that sit on Yipes metropolitan networks have 1Gbit/s connections but have a CAR for only a portion of them. This network is routinely used for traffic such as FTP traffic among offices.

If an MPLS link to an office fails, business applications run over the Ethernet network, and the PacketShapers enforce policies that give the applications priority over file transfers, Hervert says.

PacketShapers discovered an improperly configured fail-over mechanism, says Karl Greenwood, network analyst for the firm. When a site went down, traffic left it via the Ethernet backup network to the data centre, but traffic from the data centre back to the branch office was routed via the MPLS network, he says.

"The MPLS network discovered the outage and re-routed through another office," says Hervert. "It was finding its own path when it broke."

Traffic still flowed where it should, but the firm corrected the problem with AT&T because it wants to tightly control