Patton electronic 3202 manual Stays the sameused for IP routing Protocols, Express Forwarding EF

Model 3202 Getting Started Guide 4 • Web configuration

Table 12. Bits in the DSCP field

Bit 0	Bit 1	Bit 2	Precedence	Usage
1	1	1	7	Stays the same (link layer and routing protocol keep alive)
1	1	0	6	Stays the same(used for IP routing Protocols)
1	0	1	5	Express Forwarding (EF)
1	0	0	4	Class 4
0	1	1	3	Class 3
0	1	0	2	Class 2
0	0	1	1	Class 1
0	0	0	0	Best effort
Bit 3	Bit 4	Bit 5	Usage	Meaning
0	–	–	Delay	Normal
1	–	–	Delay	Low
–	0	–	Throughput	Normal
–	1	–	Throughput	High
–	–	0	Reliability	Normal
–	–	1	Reliability	High

The standardized DiffServ field of the packet is marked with a value so that the packet receives a particular for- warding treatment at each network node. RFC 2597 defines the assured forwarding (AF) classes. There are four AF classes, AF1x through AF4x. Within each class, there are three drop probabilities. Depending on a given network's policy, packets can be selected for a PHB based on required throughput, delay, jitter, loss, or according to priority of access to network services. Classes 1 through 4 are referred to as AF classes.

Table 13 illustrates the DSCP coding for specifying the AF class with the probability. Bits 0, 1, and 2 define the class; bits 3 and 4 specify the drop probability; bit 5 is always 0.

Table 13. DSCP Coding

	Class 1	Class 2	Class 3	Class 4
Low Drop	001010	010010	011010	100010
	AF11	AF21	AF31	AF41
	DSCP 10	DSCP 18	DSCP 26	DSCP 34
Medium Drop	001100	010100	011100	100100
	AF12	AF22	AF32	AF42
	DSCP 12	DSCP 20	DSCP 28	DSCP 36
High Drop	001110	010110	011110	100110
	AF13	AF23	AF33	AF43
	DSCP 14	DSCP 22	DSCP 30	DSCP 38

Advanced Configuration Options 53