LinuxQuestions.org
Download your favorite Linux distribution at LQ ISO.
Home Forums Tutorials Articles Register
Go Back   LinuxQuestions.org > Forums > Linux Forums > Linux - Networking
User Name
Password
Linux - Networking This forum is for any issue related to networks or networking.
Routing, network cards, OSI, etc. Anything is fair game.

Notices


Reply
  Search this Thread
Old 02-06-2012, 03:47 PM   #1
rladams65
LQ Newbie
 
Registered: Oct 2010
Location: Seattle, WA
Distribution: Ubuntu, Centos
Posts: 4

Rep: Reputation: 0
Using tc or iptables to control jitter (packet delay variation)


I would like to use tc to control jitter for an RTP streaming application. I am OK with introducing latency if it is a means to the ends of minimizing the jitter experienced at the streaming application.

I believe I understand how tc-tbf / tc-htb is used to shape traffic, but I am having trouble visualizing how I use these to manage a jitter buffer.

In my application there is basically no contention for the line - at least none that I am creating. Just variability caused by the public internet.

Any kicks in the right direction would be appreciated.
 
Old 02-07-2012, 11:30 AM   #2
unSpawn
Moderator
 
Registered: May 2001
Posts: 29,415
Blog Entries: 55

Rep: Reputation: 3600Reputation: 3600Reputation: 3600Reputation: 3600Reputation: 3600Reputation: 3600Reputation: 3600Reputation: 3600Reputation: 3600Reputation: 3600Reputation: 3600
Quote:
Originally Posted by rladams65 View Post
In my application there is basically no contention for the line - at least none that I am creating. Just variability caused by the public internet.
...and that AFAIK is your problem. Packet delay variation caused by Internet weather isn't something managed from either end of the connection. Handling can be suggested using QoS. Being able to ship data over a shortest route is one of the reasons for using a content distribution network.
 
1 members found this post helpful.
Old 02-07-2012, 12:11 PM   #3
baldy3105
Member
 
Registered: Jan 2003
Location: Cambridgeshire, UK
Distribution: Mint (Desktop), Debian (Server)
Posts: 891

Rep: Reputation: 184Reputation: 184
unSpawn is spot on. You can configure queuing using TC to give preferential treatment to RTP on your system, but the internet is going to take no notice of your QoS policy and for QoS to work all nodes in the transmission path need to support the same policy. unfortunately the internet does not support QoS.

What you can do is increase the jitter buffer on the application itself. If its video streaming it will help but if is bidirectional interactive traffic the increase in latency will very rapidly cause it to become unusable.
 
1 members found this post helpful.
Old 02-07-2012, 11:11 PM   #4
rladams65
LQ Newbie
 
Registered: Oct 2010
Location: Seattle, WA
Distribution: Ubuntu, Centos
Posts: 4

Original Poster
Rep: Reputation: 0
Thanks guys -- I get it.
I appreciate the confirmation that I am not missing anything ... I will work on the application's jitter tolerance.
 
Old 02-07-2012, 11:46 PM   #5
unSpawn
Moderator
 
Registered: May 2001
Posts: 29,415
Blog Entries: 55

Rep: Reputation: 3600Reputation: 3600Reputation: 3600Reputation: 3600Reputation: 3600Reputation: 3600Reputation: 3600Reputation: 3600Reputation: 3600Reputation: 3600Reputation: 3600
Quote:
Originally Posted by baldy3105 View Post
unfortunately the internet does not support QoS.
While basically true there's nuances. IMHO it would be better to say some network devices (routers, firewalls) may honor QoS...
 
Old 02-08-2012, 01:17 PM   #6
baldy3105
Member
 
Registered: Jan 2003
Location: Cambridgeshire, UK
Distribution: Mint (Desktop), Debian (Server)
Posts: 891

Rep: Reputation: 184Reputation: 184
Technically you are correct, but if one happened to it would be just because the default config uses some default queueing method that provides weighting related to QoS markings. e.g. if you installed a Cisco router on a sub 2M link you would get wfq as the default queueing mechanism which weights based on IP precedence. Its not really QoS as in an end to end service guarantee.
 
  


Reply



Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off



Similar Threads
Thread Thread Starter Forum Replies Last Post
NS-2 Packet departure delay Hannaneh Linux - Newbie 0 10-10-2011 04:50 AM
Packet Delay at Connection Startup AzraelShade Linux - Networking 1 08-03-2009 05:59 AM
Using MRTG to display packet loss and Jitter bzlaskar Linux - Networking 0 06-30-2006 11:57 PM
how to delay and drop the packet sonika_singhi Linux - Networking 4 04-02-2005 04:55 PM
packet reordering and delay using libipq shinkm Linux - Networking 0 09-08-2004 12:22 AM

LinuxQuestions.org > Forums > Linux Forums > Linux - Networking

All times are GMT -5. The time now is 05:33 PM.

Main Menu
Advertisement
My LQ
Write for LQ
LinuxQuestions.org is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
Syndicate
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
Open Source Consulting | Domain Registration