RuggedRouter User Guide
Chapter 16 – C onfiguri ng Traffic P rioritiz ation
Introduc tion
This chapter familiarizes the user with:
•Enabli ng/Disab ling Tra ffic Pri oritiza tion
•Viewin g Traffi c Priori tizatio n Stati stics

Traffic Prioritizati on Fundamental s

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: T he router mandates that you m ust have a t least a low, norm al and hig h priorit y

queue. A dditional ly, the hi gh queue m ust be of higher pr iority th an the nor mal queue,

which mu st be of h igher pri ority than the low q ueue.

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.
168 RuggedCom