HTTP proxy bandwidth

amahmood5 · ‎06-15-2005

Hi all,

I've deployed a content delivery network with a CE565 as a CDM, a CE7205 as the main root content engine and some 10 content engines at remote locations on the end of various speed links.

I have some video content on a web server. I've created a channel and replicated it out across the CDN. At a remote location, I tried to use one of the videos. I was expecting to be near instantaneous, as it would come from the content engine to the browser at local wire speeds (100Mb). However, it took about 30 seconds. The browser indicated it was coming down at 200Kb/sec

Often the cause of this kind of thing is caused by speed and duplex mismatches, bad cables, that kind of thing. Nothing I checked was at fault.

I've come back to the main office, enabled the proxy service on the root content engine (a CE7305, so plenty of power and mostly idle) and I'm getting the same 200Kb/sec throughput. If I connect directly to the origin server (all devices in this particular test are on the same 100Mb Ethernet segment) and I get near-instantaneous response.

The main reason this infrastructure was bought was to allow rich multimedia content to be distributed over low bandwidth links, then accessed at wire speeds locally.

I cannot find anything relevant to check or modify. Any help would be greatly appreciated.

The version of ACNS was left at the original version on all boxes (mainly because it's not my main role, and the frequency of Cisco's updates would make it a full time job! The only exception is these two boxes, which are on the latest rev (5.1.15.b.5).

Kind regards,

Anwar

b.hsu · ‎06-21-2005

A couple of questions to clarify... Are you seeing this problem happening at all times or only during peak hours. It can always happen that during peak hours due to the heavy traffic there may be a slight delay... And the other thing is .. Are you seeing this problem right from the day one this was deployed... or is it after some upgrade or any other changes that were made to the network. Knowing this will help in narrowing the issue.

amahmood5 · ‎06-21-2005

The CDN is currently only very lightly used; content is being acquired to distribute. The root CE at the main site is in a dedicated content acquisition role - it does not normally offer HTTP proxy services for users. Hence there's plenty of "grunt" (power) available.

During testing, and when deploying CEs at remote sites, I only really checked that I could browse the Internet - channels are relatively large, WAN links are narrow and partners restrict distribution to overnight, so its impossible to test prepositioned content at the time of installation.

I never expected, nor tested for, a ceiling on throughput. I can't say if this occurred from day one of installation, but its occurred the first time I've pushed it in any way.

I've upgraded to ACNS to 5.3.5.1 on the main CE7205 and applied the "BITRATE HTTP DEFAULT 0" parameter. This has improved things somewhat, but I'm still only getting a tiny fraction of the throughput I should (around 600K/sec). I also do not know why this would make any difference - documentation suggests this setting regulates the connection between the CE and the origin server. If I've preloaded the content on to the CE, all the CE is going to do a quick check to see I'm allowed to access the 10Mb .WMV file on the origin web server (tiny transaction), and that the one it has cached is current (tiny transaction), before serving it to me from cache at full speed.

I've attached a simple .BMP file that illustrates the situation.

Kind regards,

Anwar

jfoerster · ‎06-23-2005

HI Anwar,

could you please do a sniffer trace requesting the page. I'd like to know the http headers and all the other related stuff.

Next do you use http 1.0 or 1.1 in case of proxy usage and what do you use in case you do NOT use a proxy?

Is the proxy able to do proper DNS resolution?

Maybe you can upload the source code of the page so that we can have a look at the http settings in the page.

Kind Regards,

Joerg

amahmood5 · ‎06-24-2005

Joerg,

Many thanks for your reply. The forums do not allow uploading of files more than 3Mb. I've used the "Network Monitor Driver" in Windows XP to capture downloading http://nln.uclan.ac.uk/nln/media/nurse-1.wmv directly and via the content engine, and saved these traces to

BE WARNED - THE VIDEO FILE SHOWS GRUESOME OPEN HEART SURGERY!

http://nln.uclan.ac.uk/nln/media/ViaCE.CAP and

http://nln.uclan.ac.uk/nln/media/Direct.CAP

Whether I set Internet Explorer to use HTTP 1.0 or HTTP 1.1 when connecting via proxy servers makes no difference.

The proxy is configured with the same DNS server as the client in this test.

You can browse to http://nln.uclan.ac.uk/nln/media and you will see some files. This is just a barebones web page, but the test is valid - the large files are meant to be accelerated by the CE.

It would be interesting if someone could repeat this experiment themselves - create a channel that either crawls the URL or the specific file (nurse-1.wmv). Naturally you are not going to get a very high speed download from the origin server, but you should get wire-speed downloads from your CE.

Kind regards,

Anwar