Watching weak Internet video is about as much fun as listening to a radio with dying batteries. Lost packets lead to dropped syllables, choppy pictures and frustrated audiences.
VIPswitch, a switch vendor from Montreal, purports to deliver "flicker-free" action by giving priority to streaming audio and video traffic. It's a good idea, but when we tested one of VIPswitch's latest releases, VIPswitch 3240, we found it falls short on performance and features.
A simple Layer 2 switch at its core, VIPswitch 3240 has four 100Mbps and 32 10Mbps Ethernet ports. The ports can handle half- and full-duplex traffic, though VIPswitch 3240 supports autoconfiguration only; you can't manually set duplex parameters.
To speed multimedia traffic, the switch places all Real-time Transport Protocol (RTP) packets and User Datagram Protocol (UDP) packets with a source port number of 1024 and higher into a high-priority queue. The process is that simple - no tagging of packets, no differential services, no Resource Reservation Protocol.
There's just one problem: it's impossible to exclusively filter RTP packets, primarily because the UDP header doesn't have a protocol field to indicate the UDP payload's protocol type. In addition, there's no standard for segregating streaming voice and video packets with port numbers higher than 1023. While it's possible to pull RTP packets into the high-priority queue - which VIPswitch 3420 did in our tests - it's also possible that non-RTP packets will make it into the same fast lane.
In our tests, VIPswitch 3240 continued to pull RTP packets into the high-priority queue until the traffic load became too heavy. When traffic load on the output port reached 165 per cent of the maximum throughput for that port, the switch shut off the high-priority stream. Because a congestion rate of 165 per cent suggests it's time for a network redesign, we weren't too troubled by this.
We were concerned, however, with the results of our initial standard throughput tests. When we ran a throughput test in bidirectional, full-duplex mode with Netcom's SmartBits, VIPswitch 3240 began generating runt packets.
After some troubleshooting, we realised the SmartBits program was manually set for full-duplex mode, while VIPswitch 3240 was trying to negotiate duplex settings. Because SmartBits was manually set, it did not send link negotiation pulses to the switch. The switch defaulted to half-duplex, and error packets resulted. By configuring SmartBits for auto-negotiation, we stopped the errors. In a real network, this trait could be problematic when you need the switch to work with a device with manually set duplex parameters or an incompatible auto-negotiation mechanism.
Once SmartBits and VIPswitch started working together without errors, throughput reached only 65 per cent of wire speed for the 10Mbps Ethernet ports. When we didn't fully load each eight-port, 10Mbps module, performance improved significantly, as we expected (see www.nwfusion.com, DocFinder: 3944 for complete performance results).
Latency was pretty low, averaging 40 microsec through the 10Mbps ports at 50 per cent of maximum load.
We expected to find a slim feature set because VIPswitch 3240 is an edge switch, but we didn't expect there to be an absence of management features. Even basic management tools we would expect to find in every switch, such as the ability to check link status or packet counts, were missing in VIPswitch 3240.
The positive side to VIPswitch 3240's short feature list is that the device is easy to use and installation is a breeze. There are no serial ports to configure and no card slots for changing port cards because all ports are in a fixed configuration. In fact, the only configurable element of the switch is link aggregation on the four 100Mbps ports.
Toggling two switches on the back panel lets you group the four Fast Ethernet ports in four different configurations, ranging from four separate 100Mbps links to one 400Mbps link.
The switch is somewhat scalable because you can shift all traffic from the 32 10Mbps Ethernet ports to the four Fast Ethernet ports as traffic increases. But without management, VIPswitch 3240 would be difficult to deploy on a large scale.
We'd like to see VIPswitch beef up the 3240's feature set with basic port management tools and remote configuration options.
In its current state, VIPswitch 3240 has a workable prioritisation scheme. However, this feature is based on the assumption that most streaming voice and video traffic will travel over RTP or UDP using port numbers greater than 1023. While this is a fair assumption today, there's no way to determine that this will hold true in the future.
The bottom line ***
VIPswitch 3240 is priced at $US7995 plus $US50 for overseas postage and handling.
Orders can be placed direct with the vendor online at http://www.vipswitch.com/products/order_form.htmlCompanies interested in becoming resellers can also apply online athttp://www.vipswitch.com/resellers/resellers.html