On the architecture evolution of multilayer switching routers

In the long run, bandwidth itself is always inadequate. The smart "devices" behind the network infrastructure--switches and routers--must assume the difficult task of being intelligent to keep pace with bandwidth requirements. Applications like video and digital x-rays always require a larger, smarter "pipeline", while VoIP applications require low latency and consistent delivery rates. In the middle of the 90, with the decline of traditional switches, people began to race to develop faster, more intelligent switches and routers. A group of talented people in Silicon Valley have seen this market opportunity to invent networking hardware and compatible software based on a new concept called "Multilayer switched routing". These new "smart" switches/routers provide faster speed and shorter latency than software-based routers at the time, and can combine the capabilities of multiple network devices.

Historically, when demand for network bandwidth increases, network administrators have redesigned the network to avoid router bottlenecks. The server often bypasses the router and is reinstalled more closely away from the user. For example, a group of stock-trading workstations may be away from other devices in the company and placed with servers that provide real-time data entry for them. This is because the fewer devices that share network resources (such as routers), the more bandwidth each device can get. Traditionally, the closer the user is to the data, the faster they can get the data, because it avoids the bottleneck of the router.

In large enterprises, users are divided into smaller networks (subnets) that interconnect through routers. The basis of user partitioning is usually geographical, operational type of application, amount of data required, and security reasons. For example, the accounting department is often placed in its own group to protect the financial records of the company, not because of the bandwidth they use. VoIP phones are often placed in their own networks, so they can bypass the bottleneck of traditional routers.

When computers need to communicate with other computers that are not on their local network, they send packets to their nearest router in order to send packets to their own group. Routers provide connectivity and security boundaries between the company and the Internet, as well as connections between groups within a company (intranet).

Traditional routers are used only when absolutely necessary, such as connecting remote offices over a WAN, connecting to the Internet, and isolating the key, high-bandwidth-demanding groups in the company. Traditional routers were expensive (and still are), and there was no significant progress compared to the original design, using components similar to a standard PC and running proprietary software using multiple interface cards.

In contrast, multilayer switched routers focus all of these functions on a dedicated special application integrated circuit or ASIC. The ASIC is less expensive than traditional routers and is typically distributed across network ports. Today, a typical switch/router may include 50 ASIC in a single device that can support hundreds of interfaces. The new ASIC allows intelligent switches/routers to forward data at very fast speeds on all ports, regardless of the type of network traffic. They forward traffic at the actual interface speed (often called the line speed). Today, new switches/routers are available on the market for corporate local area networks (LANs) that can forward traffic at a single interface of gigabit bandwidth (OC-192) per second.

Problem: Core router "bottleneck"

Solution: Combine network functionality with multilayer switched routers