Multilayer switch

MultiLayer Switch (MLS) - OSI layer 3 and/or 4 A Multilayer Switch (MLS) can priorties packets by the 6 bits in IP DSCP (differentiated services CodePoint). These 6 bits was used in the "old days" for Type of Service (ToS).

The following 4 mappings are normally available in a MLS:

• From OSI layer 2, 3 og 4 to IP DSCP (if IP packet) and/or VLAN IEEE 802.1p.
• From VLAN IEEE 802.1p to IP DSCP.
• From IP DSCP to VLAN IEEE 802.1p.
• From VLAN IEEE 802.1p to port queue.

Many MLS implements QoS differentiated services and/or integrated services in hardware.

Some MLS are also able to route between VLAN and/or ports like a common router. The routing are normally as quick as switching (with wirespeed).

Layer 7 switch, web-switch, content-switch Some switches can use up to OSI layer 7 packet information, they are called layer 7 switches, content-switch or web-switch.

Some of the applications areas are load-balancing among HTTP, HTTPS and/or VPN servers. Load-balancing can be made by using NAT. Some of the layer 7 switches can NAT at wirespeed.

• Danish wikipedia (http://www.wikipedia.dk)

External addresses

• Google: Layer 3 Switching (http://directory.google.com/Top/Computers/Internet/Protocols/Transmission_Protocols/Networking_Resources/Routing/Layer_3_Switching/)
• Multilayer Switching Reference Guide (http://www.bcr.com/bcrmag/mlsreference.asp)
• Quality of Service: Delivering QoS on the Internet and in Corporate Networks (http://www.employees.org/~ferguson/QoS)
• Cisco White Paper: DiffServ-The Scalable End-to-End QoS Model (http://www.cisco.com/warp/public/cc/pd/iosw/ioft/iofwft/prodlit/difse_wp.htm)
• Survey of QoS Routing (http://citeseer.nj.nec.com/544755)
• Network Magazine 04/01/1999, Multilayer Switching: Between the Lines (http://www.networkmagazine.com/article/NMG20000509S0010) Vendors are touting switches and routers with features at layer 2, layer 3, layer 4, and beyond. Here?s how to separate fact from fiction.
• Siemens, The Solution Provider Lexikon: Web-Switch (http://w3.siemens.de/solutionprovider/_online_lexikon/0/f011680.htm)