Slicing Through the Hype of IP Switching

Layer 3 Switches: The Other Guys Unlike FastIP and MPOA, which use cut-through routing algorithms, Layer 3 switches implement traditional routing in a very untraditional way. Where software once processed data on a packet-per-packet basis, lightning-fast ASICs now speed them along in hardware. And unlike cut-through routing algorithms, which bypass your router's primary security mechanism, hardware-based routers enforce security on a packet-by-packet basis. Layer 3 Switches Pros: Offer high performance at a low cost Interoperate with existing networks Provide advanced switching features (VLANs, RSVP) Cons: Lack multiprotocol support Have limited media options Feature sets vary widely The benefits of Layer 3 switches are twofold: They provide ultra-high routing capacity at an extremely tempting price, and, in many cases, they feature the same advanced switching technologies as Layer 2 devices, such as VLANs, QoS and RMON statistics. Key players in this market include Lucent Technologies, Foundry Networks, Extreme Networks, as well as the big three--Cisco, 3Com and Bay Networks. You may be asking yourself why products like these don't hold an iron grip on the market given their price/performance value. The drawbacks to these devices are often buried in marketing propaganda. For starters, they lack the flexibility of a traditional router; many of them can route IP only, leaving legacy protocols for big-iron legacy routers. Also, when it comes to Layer 3 functionality, the flexibility of these products varies greatly. Many of them just aren't flexible enough to enforce extended access lists based on important fields such as TCP port number. In a ll cases, these products also must handle a full suite of routing protocols such as RIP and OSPF; many of them are still behind in this area, making them less than suitable for enterprise deployment. These routing protocols run on a separate processor in the box, and it remains to be proven whether that split architecture can scale to enterprise sizes. Further complicating the issue of enterprise deployment is lack of media options. Many of the Layer 3 switches crowding the market today are Ethernet/Fast Ethernet/Gigabit Ethernet-centric. A handful of vendors are promising and delivering ATM and FDDI interfaces for legacy connectivity, but the list is far from complete. WAN interfaces for ASIC-based routers are still nonexistent, relegating Layer 3 switches solely to LAN backbone applications. Second-generation devices are beginning to appear in the market. These devices feature much higher densities, more media options and more functionality. Undoubtedly, these devices will have a profound impact o n the way we do networking. Shops considering Gigabit Ethernet may very well find Layer 3 switches to be the easiest and most cost-effective solution. They certainly should be a consideration for those that rely on routers to provide interdepartmental connectivity and security. And like the other technologies presented here, Layer 3 switches can be integrated with existing LAN equipment, increasing the return on investment of your existing infrastructure. Network Computing recently took a hands-on look at the difference between Layer 3 switches and traditional big-iron routers (see "King of the Road," at www. Network Computing.com/901/901f1. html). A more complete roundup of Layer 3 switches will follow later this year. As a technology buyer, you should watch this market carefully, as new products and solutions pop up monthly, and big vendors like Bay Networks, Cabletron, Cisco and 3Com are offering new devices to compete with products from the start-up community.

For the Side Bar on How We Tested Other Features Networking in the 21st Century: The Sky's the Limit By Christy Hudgins-Bonafield