Adding ‘oomph’ to your network

Some companies operate finely tuned environments with network packets humming along at a disciplined pace; others operate at a halting cadence on shared media and cabling from the 1980s. Whichever camp you’re in, check out these tips from corporate IT veterans and industry experts for kicking the network up a notch:

1. Go jumbo. Users could squeeze more performance out of their networks with jumbo frames technology.

Switches and network interface cards (NIC) configured to support jumbo frames can process packets larger than the IEEE-standard size of 1.5Kb. Some equipment supports packets as large as 9Kb, but there is no standard packet size for jumbo frames.

“There is no doubt that for higher bandwidth Ethernet (such as Gigabit and 10G) that jumbo frames can be more efficient,” says Jeffrey Fritz, the director of enterprise network services at the University of California, San Francisco. “Now that 10 Gigabit Ethernet is here and 40 Gigabit Ethernet is on the horizon, there seems to be some resurgence of interest.”

Switch vendors with gear that supports jumbo frames include 3Com, Cisco, Extreme Networks, Force10 Networks, Foundry Networks, HP and Nortel.

The trick with jumbo frames is that switches receiving jumbo frames that are not set up to do so will drop or fragment the data. Often, switches supporting jumbo frames must be from the same vendor as well. Fritz says that implementing jumbo frames should be limited to such connections as server-to-server file transfers or back-up jobs.

2. Check your wiring. Sometimes speeding network performance is as simple as looking under a desk or into a conduit in a drop ceiling.

“There are lots of reasons people should reevaluate their cable plant and determine whether its up to snuff,” says Jim Trulove, an Austin, Tex.-based independent network consultant and the author of the books LAN Wiring: An Illustrated Guide to Network Cabling and Broadband Networking.

When bad cabling or connectors are the issue, “usually it will result in packet loss,” instead of links going completely dead, Trulove says.

This can be more of a problem. He says putting a network sniffer on a link and discovering an unusual amount of packet retransmissions is a sign there could be a problem with the cable.

Environmental factors also can cause problems, Trulove says. Wires near elevators or heating systems – which can emit electromagnetic fields – can cause problems. Shielding on cable exposed to the outdoors or in unheated conduits can crack and affect performance, Trulove says, but this can be solved by installing wire conduits with special shielding. He also recommends doing an audit of your network cabling and upgrading to at least Category 5e or 6 on all connections.

3. Turn on full duplex everywhere. Verifying the connection speeds on 10/100Mbps or 10/100/100Mbps links is another step users can take to speed up their LANs, especially as copper-based Gigabit is used more widely on desktops and servers.

“It doesn’t matter if your equipment says it has autonegotiation or not; you should verify the speeds on all links,” says David Newman, president of Network Test, a network hardware testing and consulting firm.

NICs on PCs are notorious for having the wrong settings because end users accidentally, or deliberately, change a PC from full duplex to half in software. Sometimes switches can leave the factory with misconfigured ports. Most switches come with management tools that let users view port status across all connections on the box, Newman says.

Monitoring links speeds is important in finding out if two ports have mismatched duplex settings. Newman recommends a free software tool called Multi-router Traffic Grapher that lets users view link performance and determine if duplex settings are an issue.

4. Extend Layer 3 switching to the wiring closet. Another way to boost LAN performance is to install, or turn on, Layer 3 switch features in switches connected to desktop machines.

Instead of installing a full router in the wiring closet, many switches offer basic IP routing and Layer 3-based quality-of-service features on LAN edge switches.

With Layer 3 features at the LAN edge, “you don’t have to send every bit of traffic to the big router in the sky to be routed,” Trulove says. For example, if two nodes are on separate virtual LANs but plugged into the same switch, a Layer 3 edge switch can route traffic between the two nodes. Trulove says such a network is more complex than a flat Layer 2 LAN and more susceptible to bugs. “A corrupted routing table is not something you normally have to worry about on a hub,” he adds.

5. Add route control. Implement route control or route optimization at sites that have more than one Internet connection, a configuration called multi-homing. The route-control equipment sits at such a site and is connected to the network as a Border Gateway Protocol (BGP) peer. BGP is the router mechanism that determines which Internet connection to use based on the one that requires the fewest router hops to reach the destination.

But factors other than the number of hops can slow things down. Route-control gear also can determine how much a link costs to decide the best route based on a mix of performance and price, something BGP cannot do.

Larry Pfeifer, network engineer at Widener University in Chester, Pa., uses RouteScience Technologies gear to divert traffic to the best performing of its three Internet access lines: one from Internet 2, one from Yipes Communications and one from Southern New Jersey Internet Provider.

He says the gear improves performance over BGP-chosen routes to 50,000 Internet prefixes by an average of 75.4 per cent. The improvement jumps to 95 per cent when compared to the performance change of the bottom 20 per cent of those prefixes, he says. The average time saved is 2 seconds, and 5.2 seconds for the bottom 20 per cent, he says.

Other vendors of such equipment include netVmg, Proficient Networks and Sockeye Networks.

6. Employ packet shaping. Packet shapers set traffic into queues based on application with the idea of giving key applications or delay-sensitive programs priority over others. This can be done by limiting certain applications to a certain amount of bandwidth or by blocking them altogether. The devices sit in-line with traffic as it heads toward the WAN from LAN devices, and companies such as NetReality and Packeteer make traffic shapers.

By using Packeteer equipment that gives priority to a Citrix Systems-based medical records application called MultiAccess, Western Washington Oncology in Olympia, Wash., was able to eliminate most end-user help calls.

Five offices connect to each other over the Internet via VPN, but each has a limited amount of bandwidth, a T-1 line (1.54Mbps), connecting it to the Internet. According to Craig Wyzik, IT manager for the healthcare provider, he set Packeteer gear to give MultiAccess top priority followed by laboratory applications, Web browsing and then e-mails.

Wyzik says that before installing Packeteer equipment a year ago, most Citrix-related complaints could be traced to large e-mail attachments, software downloads or file share hogging bandwidth. Since then, the source of complaints about poor performance for MultiAccess have to do with bugs in the software, he says.

7. Apply compression. WAN connections generally are too small to pass traffic as if it were on the LAN, because of the high price of long-distance bandwidth. But equipment placed at each site connected to the WAN can scan the traffic, replace repetitive patterns with shorter patterns and thereby reduce the number of bits that have to be sent across narrow WAN connections. This gives the effect of increasing bandwidth. Companies such as Expand Networks and Peribit sell this type of equipment.

The results can be dramatic. For instance, optical equipment vendor Finisar uses Peribit compression gear on links to four other company sites, one as far away as Malaysia, says Chip Greel, Finisar’s network architect. Use of the gear cuts the volume of traffic in half, letting the company connect to the Malaysia site via a T-1 connection rather than paying US$6,000 per month for a second T-1, he says. Depending on the traffic mix at the moment, sometimes traffic is reduced by as much as 70 per cent, Greel says. Without Peribit devices, boosting performance at other sites would require more bandwidth at additional monthly costs, he says.

8. Add zip to SSL. Redline Networks’ acceleration appliances speed up Internet Secure Sockets Layer transactions by reducing the number of bits it takes to transmit Web pages by 50 per cent to 70 per cent using compression and editing out data not needed for the requesting machine to build the page.

It also cuts the number of TCP requests application servers have to handle. Getting swamped by such requests can slow transaction times on busy servers to a crawl. Redline appliances create TCP sessions to the servers but then multiplex requests from many requesting machines across a single TCP session.

Redline’s equipment has saved ChartOne Medical in San Jose. from buying more Sun servers to handle access to its Web-based PeopleSoft financial application, says Henry Svendblad, ChartOne’s director of IT. The site handles more than 300,000 transactions per day. CPU use dropped from 80 per cent to 90 per cent down to between two per cent and 10 per cent. He also has been able to drop the use of terminal servers ChartOne had used a way to enable access to PeopleSoft over low-bandwidth connections.

Hochmuth and Greene are writers for Network World (U.S.).

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