Znyx Networks bh5700 manual Zcos, Marking and Re-marking, Scheduling

Marking and Re-marking

The OpenArchitect switch can mark or remark packets using the TOS field or 802.1p tag. This is also controlled through the Linux iptables utility.

Scheduling

The servicing of configured queues by the switching fabric is referred to as scheduling. The OpenArchitect switch has three built-in scheduling algorithms. The type of scheduling algorithm used is implied, rather than being explicitly specified, based on the number of queues and which options are configured. The following scheduling algorithms are provided:

First In First Out (FIFO) – When only one queue is configured per port, packets are serviced in the order in which they arrive. This is the default for the OpenArchitect switch.

Strict Priority – This algorithm is used when more than one queue is provisioned on the port. The highest priority queue, which is also the highest numbered one, is always serviced first (Example: If four queues are configured, queue three is of higher priority than queue zero). As long as there are packets in the highest priority queue, the lower priority queues are not serviced. The danger is that higher priority traffic could block lower priority traffic.

Weighted Round Robin (WRR) – This algorithm is similar to Strict Priority scheduling, but it provides fairness with quanta for each queue. Each queue is assigned a number of packets, known as weight, that it is allowed to transmit before it yields to a lower priority queue. Note that with WRR, the priorities of the queues are dependent on the weights allocated. A higher priority queue with a smaller weight will get less wire-time than a lower priority queue configured with a larger weight. Note that the same weight applies to all queues of that priority on all ports (this is a switch-wide parameter).

The zfilterd and iptables utilities are required to map packets to queues using information other than the 802.1p tags.

zcos

zcos is a tool for examining queue and scheduling settings. It provides a means to set many of the hardware features of the switch related to class of service and differentiated services processing, including scheduling and bandwidth management. The current settings can also be examined. See the zcos man page in Appendix B for details on all options.

zfilterd

zfilterd is a daemon that intercepts filtering rules entered by the user via iptables, checks them for validity and then passes them on to ztmd for entry in the switch. See the zfilterd man page in Appendix B for details on all options.

ztmd

ztmd is traffic management daemon which accepts messages from traffic filtering and quality of service applications and sets up the hardware.

Ethernet Switch Blade User's Guide release 3.2.2j page 106