RuggedCom RX1000 Configuring Traffic Prioritization, Traffic Prioritization Fundamentals, Filters

RuggedRouter™ User Guide

Chapter 16 – Configuring Traffic Prioritization

Introduction

This chapter familiarizes the user with:

∙Enabling/Disabling Traffic Prioritization

∙Viewing Traffic Prioritization Statistics

Traffic Prioritization Fundamentals

The RuggedRouter is able to prioritize traffic transmitted on network interfaces (including Ethernet, T1E1, DSL and PPP ports), giving preferential treatment to certain classes of traffic.

It is important to note that prioritization can only be applied to outbound traffic, inbound traffic can not be prioritized.

The two key elements of prioritization are traffic queues and filters. Each prioritized interface has its own unique set of these elements.

Priority Queues

Prioritization establishes a number of queues, each holding packets of differing priority. When the interface is ready to transmit a packet it selects a packet from the highest priority queue first.

If the interface is busy transmitting when packets arrive, they are enqueued in the appropriate queue.

If the interface is not transmitting when the frame arrives to be enqueued, the frame is immediately transmitted. Prioritization will not add additional delay to a stream of packets of differing priority. Prioritization will simply reorder the sequence of transmission of packets to send higher priority packets first.

Note that it is possible in indefinitely stall the transmission of packets from a lower priority queue if a traffic from a higher queue saturates the interface.

Note: The router mandates that you must have at least a low, normal and high priority queue. Additionally, the high queue must be of higher priority than the normal queue, which must be of higher priority than the low queue.

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.

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