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 an MLS:
- From OSI layer 2, 3 or 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 MLSs implement QoS differentiated services and/or integrated services in hardware.
Some MLS's are also able to route between VLANs and/or ports like a common router. The routing is normally as quick as switching (at wirespeed). According to Cisco, Layer 3 switches are basically routers that switch based on Layer 3 information, the basic difference being processing speed and/or the way they do the switching; Layer 3 switches use ASICs/hardware instead of the CPU/software that a router would.
Read more about this topic: Multilayer Switch, MultiLayer Switch (MLS)
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