O'Reilly logo

ScreenOS Cookbook by Sunil Wadhwa, Joe Kelly, Ken Draper, David Delcourt, Vik Davar, Stefan Brunner

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

14.1. Configure Policy-Level Traffic Shaping

Problem

You want to configure QoS to prioritize some traffic over other traffic, or limit traffic.

Solution

Configure egress traffic shaping on the policy by placing the policy into a priority queue and configuring optional GBW and MBW:

	set policy from "Trust" to "Untrust"  "Any" "Any " "FTP" permit
	traffic priority 3 mbw 1024
	set policy from "Trust" to "Untrust  "Any" "Any " "BGP" permit
	traffic priority 0 mbw 512
	set policy from "Trust" to "Untrust"  "Any" "Any " "MAIL" permit
	set policy from "Trust" to "Untrust"  "Any" "Any " "SIP" permit
	traffic gbw 144 priority 2 mbw 288

You can alternatively configure ingress traffic shaping with PBW instead of MBW:

	set policy from "Trust" to "Untrust" "Any" "Any " "FTP" permit
	traffic priority 3 pbw 1024

Discussion

To control packet ordering on interface buffers, configure traffic shaping in a policy. ScreenOS does not honor any ToS byte marking, such as IntServ or DiffServ bits. As explained in the introduction to this chapter, ScreenOS supports eight strict priority queues with GBW and MBW. This is a combination of strict priority and custom queuing.

MBW is used to avoid runaway queues in a strict priority scheme where a higher-priority queue can outcrowd all lower-priority queues. GBW is used to reserve bandwidth for a given policy, which is independent of priority queuing. A packet is dispatched immediately as long as GBW is not satisfied. If GBW is satisfied, traffic is sorted into the priority queue ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required