Transparent Cache; Need separation for YouTube.

Unanswered Question
Mar 31st, 2009


here I'm again trying to get some insight to my clients cache issues:

We recently wanted to separate Youtube traffic from the global cache pool and make a separate 3-cache pool, we hit a major issue, the moment we added the paramters/class-maps/policy-maps, we saw ACE dropping 80% of normal existing traffic and we were left with an outage of the web, the ACE just wont pass traffic, even after we removed the class-maps and polices and reloading the ACE module , had to reboot the c6500s

Here the config:


rserver host BCXX

description BC-YOUTUBE-x

ip address X.X.X.X


rserver host BCYY

description BC-YOUTUBE-y

ip address Y.Y.Y.Y


rserver host BCZZ

description YOUTUBE -z

ip address Z.Z.Z.Z



description Transparent Proxy Least Connection Farm


failaction purge

predictor leastconns slowstart 60

probe PORT_80

rserver BC05


rserver BC06


rserver BC07

serverfarm host YOUTUBE_FARM


failaction purge

predictor roundrobin

probe PORT_80

rserver BC-YOUTUBE-x


reserver BC-YOUTUBE-y


rserver BC-YOUTUBE-z


class-map type http loadbalance match-any YOUTUBE-1

2 match http header Host header-value ""

class-map type http loadbalance match-any YOUTUBE-2

2 match http url /get_video.*

sticky ip-netmask address both STICKY_SF

timeout 30

timeout activeconns

replicate sticky


policy-map type loadbalance first-match TRANSPARENT_LB_PM

class YOUTUBE-1

serverfarm YOUTUBE_FARM

class YOUTUBE-2

serverfarm YOUTUBE_FARM

class class-default

sticky-serverfarm STICKY_SF

, We saw some buffer crunches but not sure, we are running A2(1.3) .

last year we had same config with ONLY mathcing URL /get_video.* and was working fine with dest_ip hashing,

this time we added the host and 3 separate caches.

doesnt seem to make sense to us,

if anyone has worked to segregate U-tube , do share their config philosophy.

we are thinking about separate context or diff policies, but that's too much config related, still all options open.

do let me now champs..


I have this problem too.
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Gilles Dufour Wed, 04/01/2009 - 00:25

if you had to reboot the cat6k this is not a ACE issue.

The ACE module sits inside the cat6k but should be considered as an external device.

To separate Youtube traffic you need a new feature of A2(1.4) to hash the secondary cookie value.

CSCsq99736: ACE predictor hash url should not stop parsing at "?" delimiter

All video in youtube comes from the same url but with an option "watch?v=9LMTClqvCGs"

What you need to do is hash the value which can be done with A2(1.4).

This will guarantee that you always get to the same cache for the same video.

But your total meltdown was not the result of ACE.

Sth else must have happened.

If ACE was the problem, a reboot of ACE w/ a known-working config should have been enough.

Try not to reboot as a way to fix problems.

Call the TAC and let them troubleshoot your issue live.


shukla1975 Wed, 04/01/2009 - 03:27

absolutely right gilles ,

we have the same thought .. the funny part we had the youtube farm last year too with only matching /get_video.* just that image was (1.2)..

we have got a action plan for sunday morning and let see what happens.. TAC test bed gave +ve results, no issues with config or any bug hit , still !!

we will look at URL hash after u-tube works..till now we are just toying with various ideas.

we suspect some malloc/cpu/buffer issue between C6k and the ACE module, but where, dunno.



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