Filters, Tos prioritization – RuggedCom RuggedRouter RX1100 User Manual
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20. Traffic Prioritization
Revision 1.14.3
197
RX1000/RX1100™
20.1.1.2. Filters
For each packet to be transmitted on a prioritized interface, the packet is compared against each
of the filters on that interface until a match is found. The matching filter directs the packet onto a
specific queue. If no matching filter is found the packets Type of Service (TOS) bits in its IP header
are examined and used.
It is possible to match on source and destination IP address/mask pairs, source and destination port
numbers and protocols.
The 0.0.0.0/0 address/mask matches any IP address.
Protocols that can be matched upon include tcp, udp, icmp, ospf, vrrp and ipsec.
20.1.1.3. TOS Prioritization
The priority of an IP packet can be derived from its Type of Service field. The TOS field has the
following format:
7 6 5 4 3 2 1 0
+---+---+---+---+---+---+---+---+
| | TOS Bits | |
|PRECEDENCE |MD MT MR MMC| 0 |
| | | |
+---+---+---+---+---+---+---+---+
The four TOS bits (the 'TOS field') are defined as:
• MD - Minimize Delay,
• MT - Maximize Throughput,
• MR - Maximize Reliability,
• MMC - Minimize Monetary Cost
As any (or all) of these bits may be set in a packet at a time, there are 16 possible combinations.
The router maps these combinations into the high, normal and low priority queues as shown in the
following table:
MD
MT
MR
MMC
Descriptions
Priority Queue
0
0
0
0
Normal Service
Normal
0
0
0
1
Minimize Monetary Cost
Low
0
0
1
0
Maximize Reliability
Normal
0
0
1
1
MR+MMC
Normal
0
1
0
0
Maximize Throughput
Low
0
1
0
1
MT+MMC
Low
0
1
1
0
MT+MR
Low
0
1
1
1
MT+MR+MMC
Low
1
0
0
0
Minimize Delay
High
1
0
0
1
MD+MMC
High