layer 3 switch

(redirected from Switch router)

layer 3 switch

A network device that forwards traffic based on layer 3 information at very high speeds. Traditionally, routers, which inspect layer 3, were considerably slower than layer 2 switches. In order to increase routing speeds, many "cut-through" techniques were used, which perform an "inspect the first packet at layer 3 and send the rest at layer 2" type of processing. Ipsilon's IP Switch and Cabletron's SecureFast switches were pioneers in cut-through switching.

From Software to Hardware
As more routing lookup functions were moved from software into the ASIC chips, layer 3 switches could inspect each packet just like a router at high speed without using proprietary cut-through methods. If a layer 3 switch supports packet-by-packet inspection and supports routing protocols, it is called a "routing switch" or "switch router," which simply means "fast router." For example, Cisco calls its high-end routers Gigabit Switch Routers.

More Inspection Takes Time
The more deeply a packet is examined, the more forwarding decisions can be made based upon type of traffic, quality of service (QoS) and so on. To obtain this information requires digging into the packet's headers to ferret out the data, which takes processing time. To understand how packets are formed, see TCP/IP abc's. The following shows which data are examined at each layer. See layer 3, layer 2 switch, Web switch and virtual LAN.

TCP/IP SWITCHING/ROUTING DECISIONSLayer and      ForwardingProtocol       DecisionInspected      Based on

  2 - Ethernet   MAC address

  3 - IP         Network address
  3 - IP         Service quality

  4 - TCP/UDP    Traffic type
      socket     (HTTP, FTP, etc.)

  7 - HTTP       HTTP request type

Enterprise-class Layer 3 Switch
The BlackDiamond 6800 provided a non-blocking backplane for switching 48 million packets per second. It provided wire-speed IP routing at layer 3 and wire-speed switching at layer 2. (Image courtesy of Extreme Networks,

Enterprise Class and No Layers
In 1886, this 50-line magneto switchboard, made by Bell Telephone of Canada, was used to switch voice conversations in small localities. These instruments forged a world of switches and routers that forward billions of calls and data packets every day. (Image courtesy of Nortel Networks.)
References in periodicals archive ?
Net Insight's Nimbra carrier-class media switch router (MSR) will transport video from the fiber ring location of the House and Senate to the Library of Congress' National Audio Visual Conservation Center (NAVCC).
<p>The ExaScale system will function as an MPLS Label Switch Router (LSR), a transit router that switches packets based on MPLS labels.
The BelAir 100 Multi-Service Wireless Switch Router is a two-radio solution designed for situations where the full functionality of the four-radio BelAir200 is not required.
Worldwide Computer Products News-10 October 2001-Avici introduces scalable switch router for regional/metro POPs (C)1995-2001 M2 COMMUNICATIONS LTD
Riverstone's RS family set the standard for high-speed WAN connectivity in a broadband switch router. The RS family was the first and only family of multilayer switch routers to support the full complement of WAN connectivity--from T1 and T3 to OC-3c and OC-48c Packet-over-SONET and ATM OC-12c.
Cisco's 12000 GSR gigabit switch router delivers Internet routing and switching at gigabit speeds.
The TTSL 'Photon Pro' network features ECI's Hi FOCuS Multi-Service Access Node (MSAN) and SR9000 Carrier Ethernet Switch Router (CESR) platforms.
Unique in the industry, Marconi's entire switch-router line, scaling from 2.5 Gbps to 480 Gbps, has the ability to switch and route IP, MPLS (Label Edger Router and Label Switch Router) and ATM simultaneously.
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Leading a portfolio of 10-Gigabit Ethernet ICs, modules and subsystems for computing, storage and switch router vendors, Nortel Networks expects to begin sampling 10-Gigabit Ethernet Optical Adapters for Servers later this year.
Worldwide Computer Products News-10 January 2001-Enterasys launches new multilayer switch router (C)1995-2001 M2 COMMUNICATIONS LTD
Service providers in China are selecting the Cisco 12000 Gigabit Switch Router (GSR) series to build out New World Networks optimized for data, voice and video.