Westermo RedFox Series - Manual (Page 168)

Westermo OS Management Guide
Version 4.17.0-0
bulk data applications, such as file transfer, however, it requires that those
applications can set the IP ToS/Diffserv bits appropriately.
Use of IP ToS/DiffServ priority can be configured per port (see sections 8.2
and 8.3 ).
❼ Port Priority: Priority can be classified based on the inbound port.
Use of port priority can be configured per port (see sections 8.2 and 8.3 ).
Furthermore, when priority classification is configured to be based on VLAN
tag (or IP ToS/DiffServ), priority will be based on the port priority for un-
tagged (or non-IP respectively) packets.
When priority is classified based on VLAN ID, VLAN tag, or port priority, the pri-
ority assigned to a packet will take a value in range 0-7, and be represented by
3 bits (IEEE 802.1p). The mapping of 802.1p priority (8 values) to traffic class
(4 output queues) is shown in
table 8.2 . The rationale behind this mapping is
described in IEEE 802.1Q-2005 (Annex G).
IEEE 802.1p Queue number/
priority Traffic Class
0 0 (lowest)
1 0
2 1
3 1
4 2
5 2
6 3
7 3 (highest)
Table 8.2: Mapping of IEEE 802.1p priority to Queue/Traffic Class.
When priority is classified based on IP ToS/DiffServ, the priority assigned to a
packet will take a value in range 0-63, and be represented by 6 bits (DSCP -
Differentiated Services Code Point). The mapping of DSCP priority (64 values)
to traffic class (4 output queues) is shown in
table 8.3 . This mapping is in line
with the use of IP Precedence fields (RFC 1349), and IP DiffServ for best effort
and control traffic (RFC 2474), assured forwarding (RFC 2597) and expedited
forwarding (RFC 3246).
Packets sent out on a port with a VLAN tag will carry priority information (802.1p)
within their VLAN tag.
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