RuggedRouter
®
User Guide
Protocols that can be matched upon include tcp, udp, icmp, ospf, vrrp and ipsec.
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
1 0 1 0 MD+MR High
1 0 1 1 MD+MR+MMC High
1 1 0 0 MD+MT Normal
1 1 0 1 MD+MT+MMC Normal
1 1 1 0 MD+MT+MR Normal
1 1 1 1 MD+MT+MR+MMC Normal
184 RuggedCom
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