Networking Dilemma: Router or Switch?
- NEWSFACTOR SPECIAL REPORT
By Vincent Ryan
NewsFactor Network

It is still useful to know the traditional camp -- router or switch -- from which a product hails. But functionality, not nomenclature, is likely to distinguish the next generation of hardware products that handle network traffic.


The line that separates the definition of a router from that of a switch has been rubbed out by products and requirements that straddle the boundary. Some Layer 2 switches -- routing switches -- are chock-full of Layer 3 features that come at little additional cost and bring functionality previously reserved for routers. In many instances, enterprises that want faster traffic handling than some routers can provide can get away with a routing switch.

However, routers still are holding onto some territory, which means enterprises often must make a tough choice, not only between switches and routers, but also between products with differing amounts of Layer 3 functionality.

Homeless Hardware

Plainly stated, routers no longer have a home in the core of the network. You might have found a router there five years ago, but most certainly you have a switch today, said Yankee Group vice president Zeus Kerravala.

Multilayer switches, also called routing switches or IP switches, combine Layer 2 switching with Layer 3 routing in one box. The Passport 8600 routing switch from Nortel (NYSE: NT) Networks, for example, supports connectivity for 10-Gigabit Ethernet, ATM, PoS, and Wave Division Multiplexing. It also classifies and filters Layer 2-7 traffic at wire speed.

These multilayer boxes are faster and less expensive than traditional routers and improve performance by using hardware-based acceleration. They also boast greater port density. Throughput far supersedes the capabilities of enterprise-class routers, said Chris Kozup, a program director at Meta Group. There is little comparison between the speeds and feeds, he told NewsFactor.

As ASICS become more powerful, vendors have put more Layer 3 capabilities into switches. It's a migration from routed cores to switch-based Layer 2 networks, Kozup said. Most recently, switches also are looking to displace the router at the WAN-LAN boundary, where traditionally routers ruled.

How can they do that? Some switch vendors are offering integrated T-1 capabilities into the chassis of routing switches, Kozup said. And enterprises that source dark fiber can use routing switches to run a Gigabit Ethernet link between two sites.

In the Closet

There has yet to be a killer application that justifies putting boxes with Layer 3 functionality in the wiring closet, said Pat Patterson, a director of marketing at Nortel Networks. But some administrators are buying Layer 3 boxes because there is little or no acquisition cost difference between Layer 2 and Layer 3 switches, and administrators believe they are future-proofing their network for when that killer app comes along, Patterson told NewsFactor.

It is not that enterprises want routing in the wiring closet, Kozup said, but they do want the Layer 3 security, quality of service, and management features.

The problem with Layer 3 in the wiring closet is twofold: one, its complexity increases the amount of time I.T. has to spend configuring the switch, and therefore raises the overall cost; and two, it adds additional traffic, such as that associated with the routing table updates, to the network. Layer 3 switches have to communicate with routers upstream, so they can add additional latency, Patterson said.

Products like Nortel's BayStack 460 switch incorporate some of the features of Layer 3 routing but actually forward packets at Layer 2, Patterson said. Those features include filtering and quality of service (QoS).

Filtering reduces the number of points of access into a network and can restrict traffic -- customers want it for security, he explained.

Without QoS, traffic at the network core is best effort, Patterson said. But, as enterprises carry more and more latency-sensitive traffic -- such as streaming media and voice over IP -- they need a box that prioritizes. Without it, traffic that passes the wiring closet is at the mercy of other applications contending for bandwidth, such as a user FTP'ing a large file from a server, Patterson said.

Last Strongholds

So where does that leave the router? While Layer 3 switches can handle most of the high-volume LAN and Internet traffic, conventional routers still are necessary sometimes for connecting to wide area networks (WANs) where an organization can give up some speed in return for the flexibility routers bring.

The stand-alone router that is dedicated to determining packet destinations actually is going away. Routers are morphing into multiservice platforms with the capabilities for voice intelligence, security intelligence, and VPN connections to remote sites, Kozup said.

But some organizations can stick with routers because of their particular needs, Kozup pointed out. Typically, a company with a large number of remote sites connected over T-1s or Frame Relay circuits does not have the scalability requirements that a routing switch brings, for instance. Large enterprises need routers at the core of the WAN where high computational routing tables are required and trafficking needs are highly dynamic, Kozup said.

It is still useful to know the traditional camp -- router or switch -- from which a product hails. But functionality, not nomenclature, is likely to distinguish the next generation of hardware products that handle network traffic.


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