Switching routers answer the call for more bandwidth, performance

     The widespread adoption of high-performance switching, increased 
centralization of servers and the rapid acceptance of Internet- and 
intranet-based communications are taxing today's router-based networks.
     A next-generation communications product, known as a multilayer switch 
or a switching router, solves the connectivity and performance problems of 
today's routers and provides a foundation for growing bandwidth and 
quality-of-service (QoS) requirements.
     The switching router melds Layer 2 and Layer 3 functionality using 
hardware integration and advanced silicon. Using hardware-based 
technologies that provide multigigabits of capacity, the products provide 
scalable bandwidth and capacity to the growing number of enterprises moving 
to Fast and Gigabit Ethernet speeds.
     Switching routers perform Layer 2 switching and multiprotocol routing 
at wire speed. Such high levels of performance are achieved by integrating 
routing functionality into an Application Specific Integrated Circuit 
(ASIC). This 'router on a chip' architecture enables switching routers to 
provide many times the performance of traditional routers.
     Traditional routers use a processor to perform Layer 3 forwarding. In 
existing routed architectures, each packet is sent to a forwarding 
processor that performs next hop lookup and packet modification functions. 
When these tasks are complete, the packet is sent to the destination queue 
for delivery.
     Switching routers streamline this process in two ways. First, they 
remove the processor from the normal data forwarding path. All Layer 3 
forwarding functions are performed when a packet is received, enabling the 
packet to be queued directly to the transmit path. Second, the router on a 
chip handles Layer 3 forwarding on the fly.
     Another key performance-enhancing feature of switching routers is 
hardware-based Layer 2 and Layer 3 address resolution. In traditional 
processor-based routers, the most time-consuming activity is address lookup 
and resolution. Switching routers include Integrated Layer 2/ Layer 3 
Address Resolution Logic that performs the high-speed address lookup and 
resolution needed to deliver wire- speed performance.
     Cost savings
     In addition to dramatic performance improvements, this hardware-based 
design ap-proach produces significant cost savings. In contrast to 
traditional routers that include multiple processors, a switching router 
may be composed of only one processor, which handles topology protocols 
such as Routing Information Protocol (RIP) and Open Shortest Path First 
(OSPF). The cost savings realized through the use of ASIC technology rather 
than higher priced processors are passed on to users.
     Finally, the integration of Layer 2 and Layer 3 functions into a 
single piece of silicon reduces system costs even further. The benefits of 
this approach are clear when you compare switching router prices with those 
of traditional routers.
     When a switching router is deployed in a network, end-stations can 
communicate by means of Layer 2 or Layer 3 forwarding. The type of 
forwarding used depends on the subnet membership of the endstations. 
Subnets are portions of a network that share resources and are typically 
defined by their own net address. Traffic from endstations that belong to 
the same subnet is automatically forwarded at Layer 2, while traffic from 
stations belonging to different subnets is transported via Layer 3 
forwarding.
     Switching routers handle a full suite of protocols, including IP, RIP, 
OSPF, IPX and multicast.
     However, many networks in-clude nonroutable protocols, such as NETBIOS 
or DEC LAT, that do not recognize Layer 3 forwarding. When used in such 
environments, switching routers will automatically switch or route between 
ports depending on whether a protocol is routable.
     The hardware integration of a multiport Layer 2 switch and 
multiprotocol router into one package lets users greatly simplify their 
network infrastructure. For example, replacing one or two switches and a 
traditional router with a switching router enables multiple ports to 
perform as a switched subnet yet link to the router as a single entity.
     Switching routers also can be used to increase network efficiency and 
decrease equipment costs by supporting virtual LANs.
     VLANs are a grouping of users on a net regardless of their location. 
With switching routers, VLANs can be interconnected at Layer 2 or Layer 3. 
This allows the physical network infrastructure to be shared by multiple 
subnets. For instance, multiple broadcast do-mains or VLANs can be 
connected to a single gigabit port on a switching router.
     Multimedia applications are a driver for next-generation products such 
as the switching router. These applications require ad-vanced network QoS 
services such as QoS and multicast. Switching routers in-clude inherent QoS 
capabilities, such as priority queuing and flow control, that provide 
delay-sensitive applicationss with adequate bandwidth and consistent 
latency.
     Switching routers are the next step in the evolution of the router and 
switch. Before the advent of these products, Layer 2 and Layer 3 
technologies were often force-fit into existing environments at the expense 
of network performance and end-user satisfaction.
     Faced with increasing loads, unpredictable traffic patterns and new 
applications, users and vendors clearly saw the need for a better mousetrap.
     Demopoulos is vice president of marketing at Gigabit Ethernet start- 
up Foundry Networks, Inc.