Hello Dinesh,
We have specific combination of the 3 bits in EXP, For there combination we have the DSCP range from 0 to 63.We are defining the Class of the label as follows:-
Code Point | | |
|---|
000 | best-effort | low |
001 | best-effort | high |
010 | expedited-forwarding | low |
011 | expedited-forwarding | high |
100 | assured-forwarding | low |
101 | assured-forwarding | high |
110 | network-control | low |
111 | network-control | high |
But in actual the Diffserv model uses 6 bits of IP tos value to define the Diffserv code points(DSCP) which distinguishes how packet can be treated by the network. The first 3 bits are of EXP bits and the other 3 bits are provided by the Service Provider named as IP prec Bits, so we have two modes now:-
Default A simple best-effort class, with a DSCP value of 000000. Packets with no defined DSCP are mapped to the default class for best-effort service.
Class Selector Provides for backward compatibility with 3-bit IP PREC classes. Basically, it defines a DCSP of XXX000, where XXX represent the PREC bits.
For further, Pls go through the below link:-
http://www.atslog.dp.ua/ch04lev1sec5.html
Cheers!!!
Inderdeep
