Re: OT: Pings phenomen :)

Re: OT: Pings phenomen :)

[Jason Clark]

This is actually a function of DSL and cable modem designs, not TCP.  Hop 
onto google and ask about how a DSL modem workws, you'll get a pretty good 
explanation that I cant do justice in an email.

        Jason
www.jasonandjessi.com
It gimme the jibblies

On Sat, 28 Aug 2004, Marcin Sura wrote:

> Hi
>
>  I have 512/128 adsl. I wonder why, when I download files at full
>  speed, pings to site X are about 2000ms. But when I upload files at
>  full speed, pings to X are about 3000 to 5000ms. Can someone explain
>  this to me from tcp/ip point of view? ;)
>
> -- 
> Pozdrawiam
> Marcin                         mailto:slacklist@op.pl
>
>

OT: Pings phenomen :)

[Marcin Sura]

Hi

  I have 512/128 adsl. I wonder why, when I download files at full
  speed, pings to site X are about 2000ms. But when I upload files at
  full speed, pings to X are about 3000 to 5000ms. Can someone explain
  this to me from tcp/ip point of view? ;)

-- 
Pozdrawiam
 Marcin                         mailto:slacklist@op.pl

Re: OT: Pings phenomen :)

[Nick Taylor]

Whenever you saturate your link, the DSL modem has the opportunity to
queue packets.  You (or the remote server sending data to you, depending
on direction) are sending data faster than the line can handle it, so the
buffer starts filling up until it can't take any more.  Aparently this is
roughly two seconds worth of download or 5 second worth of upload.  2
seconds * 512kbit/sec = 1Mbit = 128Kbytes.  A fairly reasonable buffer
size.  4 sec * 128 Kbit/sec = 512Kbit = 64Kbyte.  So, you can see that it
doesn't take much data to put your modem several seconds behind the real
world.  Of course, the queue that would be active in a heavy DOWNLOAD
would be in the DSL modem at your ISP, whereas the queue that would govern
in an UPLOAD would be in your modem (assuming the ISP can retransmit your
data to the internet at 128Kbit -- they'd better).

If these ping times are frusterating to you, you might consider traffic
shaping and policing.  Check out lartc.org for info on traffic control.



On Sat, 28 Aug 2004, Marcin Sura wrote:

> Date: Sat, 28 Aug 2004 22:16:28 +0200
> From: Marcin Sura <slacklist@op.pl>
> To: netfilter@lists.netfilter.org
> Subject: OT: Pings phenomen :)
>
> Hi
>
>   I have 512/128 adsl. I wonder why, when I download files at full
>   speed, pings to site X are about 2000ms. But when I upload files at
>   full speed, pings to X are about 3000 to 5000ms. Can someone explain
>   this to me from tcp/ip point of view? ;)
>
> --
> Pozdrawiam
>  Marcin                         mailto:slacklist@op.pl
>
>

Re: OT: Pings phenomen :)

[Chris Brenton]

On Sat, 2004-08-28 at 16:16, Marcin Sura wrote:
>
>   I have 512/128 adsl. I wonder why, when I download files at full
>   speed, pings to site X are about 2000ms. But when I upload files at
>   full speed, pings to X are about 3000 to 5000ms. Can someone explain
>   this to me from tcp/ip point of view? ;)

512 is download speed
128 is upload speed

When you are uploading a file you are sucking up bandwidth on the
smallest portion of your link. This means greater congestion than when
doing a download, so the latency on your echo-request packets is higher.

HTH,
Chris

Re: OT: Pings phenomen :)

[Jose Maria Lopez]

El sáb, 28 de 08 de 2004 a las 22:16, Marcin Sura escribió:
> Hi
> 
>   I have 512/128 adsl. I wonder why, when I download files at full
>   speed, pings to site X are about 2000ms. But when I upload files at
>   full speed, pings to X are about 3000 to 5000ms. Can someone explain
>   this to me from tcp/ip point of view? ;)

I think it's just a matter of how many occasions the ICMP packets have
of going out or into your system. All the packets are put in a queue
and if the queue it's more full then the packets have to wait more to
have your ICMP packet sent or received. You are talking about uploading
files, so your ICMP packets have to wait in the queue to be sent, and
the time you get it's the time from when you sent the packet to when the
packet it's received, as you have 512 of download and 128 of upload it's
normal the queue when you are uploading it's more full and the packets
have to wait more.

It's just my guess. I'm not an expert in this kind of things and I could
be wrong.

-- 
Jose Maria Lopez Hernandez
Director Tecnico de bgSEC
jkerouac@bgsec.com
bgSEC Seguridad y Consultoria de Sistemas Informaticos
http://www.bgsec.com
ESPAÑA

The only people for me are the mad ones -- the ones who are mad to live,
mad to talk, mad to be saved, desirous of everything at the same time,
the ones who never yawn or say a commonplace thing, but burn, burn, burn
like fabulous yellow Roman candles.
                -- Jack Kerouac, "On the Road"