Traffic shaping shapes up firm's WAN performance
- 18 March, 2007 23:00
A project to consolidate servers in a central datacentre highlighted the need for global law firm Reed Smith to use traffic-shaping technology to ensure that its most important applications perform well on its 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.
Hervert doesn’t have a quantified return on investment, but the Packeteer appliances enable him to cost-justify increases or decreases in bandwidth, he says, 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 United States and six in other countries. 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 datacentre.
The centralisation is about 60% complete for the US offices and in June, the firm plans to switch its non-US offices to a new European datacentre based on the same model.
The US datacentre contains 180 Citrix servers that host the firm’s key applications, including common office applications such as Word, Excel, PowerPoint and email. “All of that processing is centralised out of one datacentre,” Hervert says. “That affords us with 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 datacentre from the carriers are separate OC-3 fiber 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 failover mechanism, says Karl Greenwood, network analyst for the firm. When a site went down, traffic left it via the Ethernet backup network to the datacentre, but traffic from the datacentre back to the branch office was routed via the MPLS network, he says.
“The MPLS network discovered the outage and rerouted 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 which traffic runs over which links all the time so it can maintain performance levels, he says.
PacketShapers also give a view of network performance that can be compared to performance numbers supplied by carriers. “Without PacketShapers, we would be relying on AT&T’s portal of bandwidth utilisation, which is very rudimentary,” says Greenwood.
The PacketShapers are also used to keep the size of WAN links optimised. For instance, when the firm recently opened a new office in Chicago, it bought the full bandwidth on a DS-3 during the period that files were being uploaded from the office to the data-centre.
But when those uploads were completed, it planned to reduce its bandwidth commitment to fit the demands of routine traffic, Hervert says. “We can reduce costs by saying, ‘We’ve gone a month here and PacketShaper says the Chicago office peaks at 5Mbit/s.’ We can go back to our carriers and lower our CAR values,” he says.
Reed Smith uses PacketShapers to limit bandwidth available to unauthorised traffic and to automatically identify and monitor new types of traffic as they are discovered. The PacketShaper can limit bandwidth available to recreational traffic such as peer-to-peer or in some cases block it altogether, he says.
Reed Smith uses a feature of PacketShapers called adaptive response to address unexpected events that might affect network performance. Based on policies the firm sets, for example, if an office generates more than 75% of total traffic, the Packeteer devices send an alert.
Alternatively, if a particular application generates traffic outside the norm, the gear automatically creates a separate traffic class for it. The new class jumps out when Hervert reviews routine network performance reports, he says. The gear also generates an email about the spike in traffic.
The firm does not take advantage of Packeteer’s ability to compress traffic across WAN links. So far, there is enough bandwidth to keep performance high without it, says Hervert.
The goal is to get the Citrix traffic and voice traffic among offices running well, then add IP video to the mix over time, he says.
“The PacketShape is our view, our measurement of what’s there, of what’s behaving on the network and what we can add to it,” Hervert says.