Ip Tos / Diffserv - Hirschmann RS20 User Manual

Network load control
End-to-end prioritizing requires the VLAN tags to be transmitted to the en-
tire network, which means that all network components must be VLAN-ca-
pable.
Routers cannot receive or send packets with VLAN tags via port-based
router interfaces.

7.4.3 IP ToS / DiffServ

TYPE of Service
The Type of Service (ToS) field in the IP header
part of the IP protocol from the start, and it is used to differentiate various
services in IP networks. Even back then, there were ideas about differen-
tiated treatment of IP packets, due to the limited bandwidth available and
the unreliable connection paths. Because of the continuous increase in
the available bandwidth, there was no need to use the ToS field. Only with
the real-time requirements of today's networks has the ToS field become
significant again. Selecting the ToS byte of the IP header enables you to
differentiate between different services. However, this field is not widely
used in practice.
Bits
0 1
Precedence
Bits (0-2): IP Precedence Defined Bits (3-6): Type of Service Defined Bit (7)
111 - Network Control
110 - Internetwork Control
101 - CRITIC / ECP
100 - Flash Override
011 - Flash
010 - Immediate
001 - Priority
000 - Routine
Table 5: ToS field in the IP header
Basic Configuration L2P
Release 4.2 07/08
2 3 4
Type of Service
0000 - [all normal]
1000 - [minimize delay]
0100 - [maximize throughput]
0010 - [maximize reliability]
0001 - [minimize monetary cost]
(see table 5)
5 6 7
MBZ
7.4 QoS/Priority
has been
0 - Must be zero
113