What does 10100000 mean in the ToS byte?

Answer 1

First 6 bits are DSCP bits and the last 2 are ECN bits (ECN = Explicit Congestion Notification)

The above answer is right when we look at these bits from Diffserv perspective.....

Let me clear what it means interms of Intserv perspective and what are the network models...

Basically there are two types of network models...1)Intserv - Integrated services

2)Diffserv-Differentiated Services

When the Pkt is in intserv region/domain these 8 bits refers to TOS byte : Type of Service Filed. Here the first 3 field are precedence bits and the next 4 bits are TOS bits and the Last bit is MBZ(Must Be Zero)

In the Question above 10100000 : the First 3 PRECEDENCE bits (101) refers to critic/ecp as shown the below table

111 - Network Control

110 - Internetwork Control

101 - CRITIC/ECP

100 - Flash Override

011 - Flash

010 - Immediate

001 - Priority

000 - Routine

The Next 4 bits describes following states :

Bit 3: 0 = Normal Delay, 1 = Low Delay.

Bits 4: 0 = Normal Throughput, 1 = High Throughput.

Bits 5: 0 = Normal Reliability, 1 = High Reliability

Following is the semantics for the bits 3-6 of the IPv4 TOS octet:

1000 -- minimize delay

0100 -- maximize throughput

0010 -- maximize reliability

0001 -- minimize monetary cost

0000 -- normal service

So in the above quest bits 3-6 refers to 0000 which means normal service ..and the last bits as mentioned above is always MBZ.

W.r.t Diffserv Domain the interpretation of these fields is already explained in the First answer i.e,. DSCP bits and ECN bits ...