Multilayer switch

A multilayer switch (MLS) is a computer networking device, that switches on OSI layer 2 like an ordinary network switch - and provides extra functions on higher OSI layers.

Table of contents

1 MultiLayer Switch (MLS) - OSI layer 3 and/or 4 2 Layer 7 switch, web-switch, content-switch 3 External addresses

MultiLayer Switch (MLS) - OSI layer 3 and/or 4

A Multilayer Switch (MLS) can prioritize packets by the 6 bits in IP DSCP (differentiated services CodePoint). These 6 bits were 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 portss 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.

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Sources/references

• Danish wikipedia

External addresses

• Google: Layer 3 Switching
• Multilayer Switching Reference Guide
• Quality of Service: Delivering QoS on the Internet and in Corporate Networks
• Cisco White Paper: DiffServ-The Scalable End-to-End QoS Model
• Survey of QoS Routing
• Network Magazine 04/01/1999, Multilayer Switching: Between the Lines 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