Re: [LARTC] Theory test

[Andy Furniss <andy.furniss@dsl.pipex.com>]

Kenneth Kalmer wrote:
> On 12/6/05, Andy Furniss <andy.furniss@dsl.pipex.com> wrote:
> 
>>Kenneth Kalmer wrote:
>>
>>
>>>ADSL, 512kbps down and 256kbps up. Parent for the internet traffic is
>>>set at 500kbps, to make sure it becomes the bottleneck...
>>
>>I used to use 400 when I had 512 ingress, so I am amazed that works -
>>but then you say ingress not the problem.
> 
> 
> I'll tone it down to see if it makes a difference, but I need to keep
> it as close as possible to the 512 because the line gets very
> congested...

Yes 400 may be a bit far I used it because latency was important to me.

Remember queueing traffic on the wrong end of a bottleneck is not ideal 
- if you want to run at 99% then the queue will only grow 1 packet for 
every 100 it passes - useless really. You need to be the one that 
decides which packets get dropped to have some influence over the 
sharing out of the bandwidth - too close to the limit and the dropping 
will just happen at the isp/teleco FIFO.

It's for the same reason that I am concerned about queue length - if 
it/they are too long then the other end won't know about the tail drop 
quickly enough as it will take time for the packets infront to clear. (I 
hacked esfq to head drop for this reason - though there are issues with 
it to do with imq that I haven't sorted yet. It seems to work and is 
stable for me, but could do with a bit more rigorous testing).

> 
> 
>>>I attach an esfq to each child HTB, but as you say it would be less
>>>relevenat for egress...
>>
>>Were it ingress I woud say have just one class with esfq for sharing out
>>bulk traffic per user.
> 
> 
> I meant on traffic going to the network (egress) I attached an esfq to
> each users' limit

Hmm - maybe our ingresses and egresses are getting confused - when I say 
ingress I refer to traffic coming in on the bottleneck (internet) link - 
even if you are shaping it as egress on your lan facing interface.

So to be clear the Problem is actually what I call ingress - the 512kbit 
traffic - yes?


> 
> 
>>>>Do you know what type of connection you have eg pppoa/e or bridged ip
>>>>etc. I assume whatever it is ends up as atm cells?
>>>
>>>Barely, as said above it's 512/256 VPN. Underneath the VPN it runs
>>>PPPoE, but the service simulates a leased line, static ip's, the
>>>works...
>>
>>I bet there are alot of overheads on that - and if you are pushing the
>>rate close to limit like you are on ingress I suspect you are going
>>overlimits. Even if you test with an upload and find a rate that seems
>>OK it will all fall apart when the traffic consists of small packets.
> 
> 
> Amazingly not, we have the same line in the office, no shaping, and we
> often sustain 110% capacity for very long periods of time. I believe
> the provider uses very heavy compression on the line. Still, it's
> blazingly fast compared to the traditional ADSL offerings available
> here.

Nice in some ways, but if compression is being used you effectivly have 
variable bandwidth depending on traffic type, which is going to be a 
pain to set a rate for. Are you sure it's compression and not a more 
generous sync rate - your modem should tell you - it would be 
interesting to know.

> 
> 
>>You have real ips aswell 

> The students are NATted, and firewalled to hell and back, so
> filesharing is not a problem. They try, but who wouldn't...
> 

Ahh OK.

Andy.

PS - I am getting undeliverable mails when replying in this thread.

Failed to deliver to '6734440@sms.tele2.lv'
SMTP module(domain terminator.swip.net) reports:
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