Dropped packets giving you grief? Out-of-order packets messing with application performance? Silver Peak Systems says it can help tame these problems with the latest enhancements to its WAN acceleration gear.

New features from Silver Peak are designed to overcome dropped and misordered packets to improve throughput, particularly on high capacity WANs that can be prone to such problems, says Jeff Aaron, director of product marketing at Silver Peak. In MPLS and IP VPN environments, where routers and links are often oversubscribed, packet delivery issues can increase as throughput increases, for example. It’s common to see averages of 0.5% packet loss with peaks reaching 1%, 2% or even 5%, Aaron says.

These problems can lead to excessive retransmissions, which in turn slows data transfers across the WAN.

“As a general rule, packet loss is a bigger issue on bigger pipes,” Aaron says. “If you’ve got a T-1, and you hit packet loss, you can probably use TCP and retransmit and your application may be a bit slower, but traffic will still show up. But if you're doing replication at 100Mbps and you start to drop packets, and your throughput goes down to about 5Mbps, that’s pretty catastrophic. Those applications are going to get broken.”

Jim Metzler of analyst firm Ashton, Metzler & Associates, likewise said packet loss and reordering can debilitate key applications across the WAN, “especially in data replication and remote backup scenarios where there are large amounts of sustained traffic.”

“As more enterprises move to MPLS and IP VPNs, loss mitigation and reordering techniques will become an increasingly important requirement for WAN optimization devices,” he said in a statement.

To expose -- and overcome -- packet loss and ordering issues, Silver Peak gear depends on a few techniques:

* Dynamic forward error correction (FEC): FEC technology is used to reconstitute lost packets at the far end of a WAN link in real-time, eliminating the need to retransmit lost data. Silver Peak has offered FEC since 2005. In its latest software release, Silver Peak expanded its ability to work on high capacity links; the current FEC technology can support up to 2Gbps of LAN traffic and 500Mbps of WAN traffic.

* Packet order correction: Silver Peak’s NX appliances resequence packets on the far end of a WAN link, prior to delivery, to avoid re-transmissions that occur when packets arrive out of order. “On the far end, if packets are delivered out of order, rather than having to retransmit using TCP, we can reorder them and deliver it to the host,” Aaron says. “This is ideal for real-time traffic, because you’re avoiding the need to have to retransmit, which basically would break replication, voice and video applications.”

Ann Bednarz is associate news editor at Network World.