In the first part of this series on switch testing, we explored how to test 10 GbE switch latency. In part 2, we looked at benchmarking core switches. In the third part, we outline features to consider when choosing an edge switch.
Edge switches may not be as powerful or expensive as 10 GbE core switches, but it is just as important to evaluate these products before investing. Given the bevy of edge switch features to choose from, the evaluation process can be even more confusing.
Testing raw performance may be the focus of core switches, but that isn't necessarily what to consider when choosing an edge switch. Stripped of their ancillary functions, edge switches route traffic from the office LAN across the WAN, usually to another office or corporate data center. Thus, the basic job of the edge router is just plain easy. It doesn't take advanced software or computational capacity to take data coming in from a Fast Ethernet or Gigabit Ethernet LAN port and queue it for transmission across a WAN port that is running at speeds of a few megabits per second. And given that most edge switch vendors use switch silicon from vendors like Broadcom, it is likely that the basic switching capabilities will work as advertised.
Edge switch functions to consider before investing
Routers enable firewall and VPN tunnel termination: These are almost standard offerings now and don't require a lot of horsepower since the WAN link speed will throttle down traffic to and from these WAN-oriented functions.
Added functionality on the LAN side of the router: Some vendors take an even more aggressive "all-in-one" approach to the edge switch integrating advanced security functions like IPS and malware-scanning. These switches may even have integrated wireless access points. Given the amount of processing power typically available in an edge switch, it is possible to load a lot of functionality in a modest little edge switch. While these functions are separate from basic edge switch functions, combining them means fewer devices to manage.
It is increasingly common to find that the edge switch will offer 24 LAN ports supporting Power over Ethernet (PoE) for VoIP phones, WLAN access points and so on. Currently, we are transitioning to next-generation PoE Plus, which provides higher power to connected devices. To my knowledge, one cannot upgrade PoE to PoE Plus. So, if you need it, make sure your switch is PoE ready.
It is important to investigate the processor and RAM specifications for multi-function devices. While requirements may vary, look for multiple gigabits of RAM and a multi-core processor. I was surprised recently when I saw a leading (and expensive) Web security device come equipped with only 512 MB of memory. It was not enough to store all the virus signatures needed for our testing.
Considering open source when choosing an edge switch
Even though throughput and scalability aren't likely to be major issues for your edge switch, tests over the years have shown that edge routers built on off-the-shelf, standard Intel platforms can outperform many vendors' purpose-built multi-service routers.
A look at two different Tolly tests of Vyatta routers running on Dell servers proves the point. In tests, Vyatta software beat out Cisco Integrated Services Routers (ISRs) on speed and border gateway protocol (BGP) performance. The production volumes of systems built using off-the-shelf hardware components, combined with the cost efficiencies of using a commercial or open-source OS, are reflected in the lower price.
There can be occasions when a proprietary appliance can be what you need -- and this is true for more than just edge routers. If the functions you want to deploy require a specialized OS and/or performance or functionality only available in custom ASICs, you will probably need to find an appliance-based solution that meets your particular requirements.