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On Demand Bandwidth Utilization

 
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Anonymous
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PostPosted: Mon Sep 05, 2005 4:01 am    Post subject: On Demand Bandwidth Utilization Reply with quote

I currently use Shoutcast's on-demand feature to stream content. Shoutcast doesn't stream on-demand content at the bitrate of the requested MP3 file. Rather, it shoves the file to the audio client as fast as the client will accept it. This means that my upstream bandwidth graph is loaded with spikes, one spike for every song that gets requested on-demand. Spikes are bad. Spikes mean I have a congested pipe and that other things are suffering until the spike goes away.

So the question is this...does Icecast stream on-demand content at the bitrate of the requested MP3 (true streaming)? Or does it do the same thing Shoutcast does - shove the file out the pipe just as fast as the audio client can take it (pretty much a file download)?
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karlH
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Joined: 13 Jun 2005
Posts: 5476
Location: UK

PostPosted: Mon Sep 05, 2005 2:53 pm    Post subject: Reply with quote

Icecast pushes the file data at the speed the connection will allow, doing true streaming for files would mean parsing the mp3/aac/nsv contents to regulate the rate and that is something we don't do. We could do it for Ogg files as that is a free codec but for consistency sake we don't.

karl.
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Anonymous
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PostPosted: Fri Sep 30, 2005 1:36 am    Post subject: Cisco - Generic Traffic Shaping Reply with quote

I did find a way to limit bandwidth utilization in my environment. Using a Cisco router, I used the "traffic-shape" statement in an interface paragraph to categorize my streaming audio traffic, and cap its max utilization. If you're not a Cisco person, maybe you don't care...but I thought I'd post it for posterity since it's working like a champ.

Assuming you've got a Cisco router with 2 ethernet ports, the following code will be useful to you...this is IOS 12.2 code, although generic traffic shaping was introduced in earlier IOS families. This is not comprehensive code for the whole router, just the stuff I put in to shape traffic. Also, let's assume in this example you've got 768Kbps upload capacity from your ISP.
Code:
interface FastEthernet0/0
 description OUTSIDE - Internet connected interface
 traffic-shape group 113 192000 7872 7872 1000
 traffic-shape group 115 768000 19200 19200 1000

access-list 113 remark ----------------------------------------------------------------------
access-list 113 remark TRAFFIC SHAPING, 192Kbps cap (keeps audio on-demand from spiking
access-list 113 remark the line).
access-list 113 permit tcp any eq 8000 any
access-list 115 remark ----------------------------------------------------------------------
access-list 115 remark TRAFFIC SHAPING, 768Kbps cap (queues up as yet unshaped traffic if
access-list 115 remark utilization exceeds 768Kbps). This only kicks in if:
access-list 115 remark (A) bandwidth utilization is more than 768Kbps &
access-list 115 remark (B) the packet isn't getting shaped by a different traffic-shape
access-list 115 remark statement already.
access-list 115 permit ip any any

Read more about it here:
http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_configuration_guide_chapter09186a00800bd8ef.html
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