Cisco Catalyst 4948-10GE aces performance tests

In an exclusive Network World test, Cisco's Catalyst 4948-10GE delivered record low latency and line-rate throughput. Coupled with innovative security mechanisms and an extensive list of switching and routing features, this switch earns a Clear Choice award.

With a price of $30,000, the Catalyst 4948-10GE is too costly to be deployed in every wiring closet, but the price makes sense for use in data centers where the switch can aggregate connections from many servers and send traffic over a 10-Gigabit Ethernet backbone.

The Catalyst 4948-10GE offers 48 copper Gigabit Ethernet and two 10G Ethernet ports, much like competing products from Extreme Networks, Force10 Networks and Foundry Networks. There are some key differences, though: The Cisco switch has a 1-rack unit (1.75-inch) form factor, while Foundry's FESX448 occupies 1.5 rack units. The Cisco switch supports redundant power supplies, while redundancy for Extreme's S400-48t requires one external power supply (however, Extreme's external power supply can be shared across multiple switches). On the downside, Cisco's device is not expandable, unlike Force10's S50, and its list price is higher than similarly configured competitors' switches.

Perhaps the biggest difference is Cisco's use of X2 transceivers for 10G Ethernet interfaces. These are roughly the size of Gigabit Ethernet transceivers, putting them about halfway between 10G Ethernet Transceiver Package (XENPAK) transceivers and smaller 10 Gigabit Small Form Factor Pluggable transceivers (XFP) in newer 10G switches from Force10, Foundry and Nortel, among others. One consideration for adopters of multiple transceiver types is that they'll have to keep multiple types of spares on hand, with prices well into the thousands of dollars for each.

X2 transceivers are functionally identical to XENPAK transceivers, while XFP transceivers offload the serializer/deserializer (Serdes) function to the switch's circuit board. Cisco says X2s boost reliability because a Serdes failure requires replacement of just a transceiver rather than an entire switch. We're not sure about that claim: While it's still relatively early for XFPs, we've yet to junk an XFP device because of a Serdes failure. We did verify that X2 transceivers interoperate with both XENPAK and XFP transceivers over single-mode fiber cabling.

Peak performance

We stress-tested the Catalyst 4948-10GE in various configurations, and it came up aces in all of them. These configurations involved Layer-2 and -3 switching, virtual LANs (VLAN) and Open Shortest Path First (OSPF ) routing, all common tasks for an aggregation switch. We also measured the switch's buffering and unicast address learning capacity.

We pounded the switch with a traffic pattern that involved fully meshed traffic between all 48 Gigabit Ethernet ports, as well as traffic between the two 10G Ethernet ports (see How we did it ). No production network (hopefully) ever sees traffic like this, but it does allow us to determine the limits of system performance.