| | QoS - Quality of Service
Layer 2 markings:
- CoS: Class of Service, used with Ethernet trunks (only on
trunks, as basic eth. frame has no means to carry CoS information). 3 Bits,
000 is best effort.
- DE: Frame Relay, Discard Eligibility, one bit only.
- Exp-bits: MPLS, very similar to CoS on ethernet
trunks
Layer 3 markings:
- ToS: Type of Service. 1 Byte in IP header. Before used as
"IP Precedence" which only used 3 bits, now used as "DSCP"
(Differentiated Service Code Point) which uses 6 bits.
3 basic models:
- Best-Effort
- Integrated Services (IntServ)
- Differentiated Services (DiffServ)
Best -Effort
The usual stuff, nothing to configure. Switches and routers just do the job
as good as they can, no distinction of protocols or classes.
Integrated Services (IntServ)
Reserving bandwidth for a specific communication (e.g. VoIP call) across the
entire network by means of RSVP.
Needs support of RSVP over all concerned
network equipment. Reserved bandwidth can not be used, even if the reserving
stations don't use it.
Differentiated Services (DiffServ)
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