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How Fast is a T1? really.

 
 
Toby
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Posts: n/a
 
      11-29-2004

"john" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Hi all:
>
> I just successfully turned up a T1 from NYC, US to Manila, Philippine.
> Both routers are Cisco 2600.
>
> The ping time is about 268ms, every time.
>
> My questions:
>
> How fast is a T1 really? we're going to do VOIP and we're going
> to use g723 codecs and we want to know how many "agents" can
> be on the T1. I heard someone once said that a T1 is about 200k
> per second.
>
> What is the usual ping time from here to a country like Philippine or
> India, anyone knows?
>
> Thank you all!.
>
>

Hi John

Firstly a true T1 is a point to point link and can not slow down or speed up
so without congestion causing delays inside the router due to queing or CPU
exhaustion all traffic should reach the destination in the same time.

The speed of a T1 link is 1.544M unchannelised or 1.536M if channelised into
24 slots.

As for RTD if this was a true T1 link and we can ascertain that the
local/remote routers are not under any processing strain due to any other
connections etc.and we were not trying to overutilise the link from time to
time (no queing) then this would not vary. The bulk of the RTD would be
propogation delay. i.e. distance related and can only be improved by
shortening the distance. I hear people whince here as we can't move the US
closer to the Philapines. The truth is though that the cable routing might
not be as straight as you think (but this is probably not your problem). All
assumtions in this news group have been based on your testing (quite
rightly) but can you confirm you are only testing the link by pinging the ip
address each end of the link. If this is a proper T1 link then there is no
real need to try to load the link for this as you cant slow down a T1 link,
the RTD should be pretty constant, again assuming no CPU/Queing problems.

Some good fellow on this thread has done a lot of maths and concluded that
this must be a really long routing to get the RTD you are getting. which is
good evidence that you havent got a dedicated link at all to the phillapines
but a T1 link to a service provider to be onwardly forwarded via frame
relay/ATM etc. This will mean that your traffic will get switching delays as
well as queuing delays and possibly discards depending on your service
contract. One sure fire way of finding out if you have a point to point cct
is to change the encapsulation type at both ends from what ever you are
using to a different type and see if it still works (sensibly with a planned
outage of course). If you are running frame relay encapsulation though you
can have a good guess by looking at the config of the 2 routers. On a point
to point cct then one router must be running Frame-Relay Switching and also
this routers interface will also be running Frame-Relay Intf-type DCE. If
they are not you are using a frame relay network in-between each site with
switches etc. There are probably checks for other types of encapsulation
also but I can't advise here.

If you ascertain that you are in fact running through other networks then
you will need to contact your service provider to be able to give priority
to your voip traffic over the link. This can be done in frame-relay via 2
pvc's being used one for voip and the other for data. but this can only be
discussed/cured by your service provider and no one here on this group. If
your service provider can not give you what you need at the price you need
the I'm afraid it's back to shopping around.

Toby



 
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stephen
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Posts: n/a
 
      11-29-2004

"john" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
>
> "Erik Freitag" <(E-Mail Removed)> wrote in message
> news(E-Mail Removed)...
> > On Sun, 28 Nov 2004 22:45:24 -0500, John R. Levine wrote:
> >
> >>>> I just successfully turned up a T1 from NYC, US to Manila,

Philippine.
> >>>> Both routers are Cisco 2600.
> >>>>
> >>>> The ping time is about 268ms, every time.
> >>>>
> >>>> My questions:
> >>>>
> >>>> How fast is a T1 really?
> >>
> >>>Well, a T1 is 24*64K=1536Kbs + 8Kbps for telco overhead, but I think
> >>>you're asking about latency. Looks like yours is about 268ms, using

some
> >>>simplifying assumptions (speed of light in fiber at around 2/3 vacuum =
> >>>200000 km/s, no latency in telco equipment), this means that the

network
> >>>distance from New York to Manila is about 33000 - 34000 miles. Seems a
> >>>bit
> >>>long for a planet with a 24000 mi diameter, unless you're going the

long
> >>>way 'round.
> >>
> >> No kidding, the air distance is about 8500 miles. 1/4 second sounds
> >> about right for a geosync satellite hop. It's hard to imagine why
> >> you'd get a satellite link with the glut of fiber, but it should be
> >> easy enough to ask.

> >
> > Got a correction from
> >
> >> Kirjoitit ryhmässä comp.dcom.sys.cisco:
> >>
> >> You need to divide that with two, ping time is RTT. So infact
> >> it's network distance to new york to manila to new york.
> >>
> >> HTH,
> >> --
> >> ++ytti

> >
> > I was wrong, and this is correct, so the "network distance" is really
> > 16500 - 17000 miles. Or about twice the actual distance, so it still
> > sounds a bit slow. Do you have engineering documents from your carrier?
> > They might have some hints.


If this is a "real" T1, then it may be protected by SDH - the numbers look
more like the circuit could be going "the wrong way" around the world -
which is quite possible with sdh and a telco not forcing the shorter
path....
> >
> >

>
> Hi all:
>
> Thanks for the fascinating information. I could ask the carrier to see
> what they have. Is there something specific that I can ask from them
> or just a broad question?


ask for the circuit routing, and expected latency - then check if it looks
close to what you expect.

if you have internet access at both sites - try a ping via the internet to
compare the results.

i have seen a european cross border circuit routed via the US after a fault
which gave similar differences between expected and actual latency.
>
> Maybe I should set up an ftp server on the US or Manila side and
> do around 10-20 ftp sessions and average out the result to find the
> "real" speed.


this houldnt affect the latency, but the ping results may vary if you start
having Qing in the routers.
>
> How about that?
>
> TIA.
>
> John.

--
Regards

Stephen Hope - return address needs fewer xxs


 
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H Brett Bolen
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Posts: n/a
 
      11-30-2004
"john" <(E-Mail Removed)> wrote in message news:<(E-Mail Removed)>...

> How fast is a T1 really?



1.544 Mbps --- about as fast as a 1x cdrom reader.


 
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john
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Posts: n/a
 
      11-30-2004

"T. Sean Weintz" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> john wrote:
>> Hi all:
>>
>> I just successfully turned up a T1 from NYC, US to Manila, Philippine.
>> Both routers are Cisco 2600.
>>
>> The ping time is about 268ms, every time.
>>
>> My questions:
>>
>> How fast is a T1 really? we're going to do VOIP and we're going
>> to use g723 codecs and we want to know how many "agents" can
>> be on the T1. I heard someone once said that a T1 is about 200k
>> per second.
>>
>> What is the usual ping time from here to a country like Philippine or
>> India, anyone knows?
>>
>> Thank you all!.
>>
>>
>>

> Ping latency has nothing to do with the speed of the line. Latency has to
> do with the speed of routers and switches on the route.
>
> Sincve I seriously doubt you actually have a pt to pt T1 between the US
> and phillipines, you must be going over frame relay, atm, vpn, or
> something. Need to know extacly how the T1 connects you to the phillipines
> to be able to say why the latency is so high.
>


This is what the carrier emailed me back:


>>>

It was technically provisioned via our Freeway Service which is our direct
connection to LA.

Freeway runs on ATM over C2C-JUNC cable routes.



-John


 
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Hansang Bae
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Posts: n/a
 
      11-30-2004
In article <(E-Mail Removed)>, http://www.velocityreviews.com/forums/(E-Mail Removed) says...
> Thanks for the fascinating information. I could ask the carrier to see
> what they have. Is there something specific that I can ask from them
> or just a broad question?
> Maybe I should set up an ftp server on the US or Manila side and
> do around 10-20 ftp sessions and average out the result to find the
> "real" speed.
> How about that?


300ms to parts of Asia from US is not unreasonable. But if you're doing
bulk file transfer over high latency pipes, you need to consider RFC
1323.

--

hsb

"Somehow I imagined this experience would be more rewarding" Calvin
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T. Sean Weintz
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Posts: n/a
 
      11-30-2004
john wrote:
> "T. Sean Weintz" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
>
>>john wrote:
>>
>>>Hi all:
>>>
>>>I just successfully turned up a T1 from NYC, US to Manila, Philippine.
>>>Both routers are Cisco 2600.
>>>
>>>The ping time is about 268ms, every time.
>>>
>>>My questions:
>>>
>>>How fast is a T1 really? we're going to do VOIP and we're going
>>>to use g723 codecs and we want to know how many "agents" can
>>>be on the T1. I heard someone once said that a T1 is about 200k
>>>per second.
>>>
>>>What is the usual ping time from here to a country like Philippine or
>>>India, anyone knows?
>>>
>>>Thank you all!.
>>>
>>>
>>>

>>
>>Ping latency has nothing to do with the speed of the line. Latency has to
>>do with the speed of routers and switches on the route.
>>
>>Sincve I seriously doubt you actually have a pt to pt T1 between the US
>>and phillipines, you must be going over frame relay, atm, vpn, or
>>something. Need to know extacly how the T1 connects you to the phillipines
>>to be able to say why the latency is so high.
>>

>
>
> This is what the carrier emailed me back:
>
>
>
> It was technically provisioned via our Freeway Service which is our direct
> connection to LA.
>
> Freeway runs on ATM over C2C-JUNC cable routes.
> -John


Which doesn't tell very much, other than it is not a true point to point
T1. For starters what the heck are "c2c-junc" cable routes? Google
search on that term turns up nothing.

The latency is obviously occuring in the ATM cloud. Since I am not
familial with the topology of their "freeway service", I can't tell you
where or why.


 
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Toby
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Posts: n/a
 
      11-30-2004
Have you asked the service provider what latency your service contract
should expect from the US to the Philapines. With Layer 2 switching such as
ATM they usually can provide maximum figures.

You can expect that a pure T1 whould be the fastest as there are no queues
to manage and virtually negligable multiplexing delays. ATM uses a shared
network and as such will induce switching/queing delays and these can be
expected although ATM switching is very fast and queing is only due to
congestion either on your access link or within the SP cloud. It is
provided as a cheaper alternative to dedicated point-point links as it is
shared but still the service provider should provission there bandwidth to
accomodate the traffic levels expected and only penalise the abusers.

If the SP is not providing what they have prommised get them to re-route the
ATM PVC. If they are remember we can't change the laws of physics and also
shouldn't expect perfection on a budget. Of course you would still have a
claim if the service has been mis-sold to you on these accounts.

Toby


 
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James Lewis
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Posts: n/a
 
      12-01-2004
john wrote:
> "Erik Freitag" <(E-Mail Removed)> wrote in message
> news(E-Mail Removed)...
>
>>On Sun, 28 Nov 2004 22:45:24 -0500, John R. Levine wrote:
>>
>>
>>>>>I just successfully turned up a T1 from NYC, US to Manila, Philippine.
>>>>>Both routers are Cisco 2600.
>>>>>
>>>>>The ping time is about 268ms, every time.
>>>>>
>>>>>My questions:
>>>>>
>>>>>How fast is a T1 really?
>>>
>>>>Well, a T1 is 24*64K=1536Kbs + 8Kbps for telco overhead, but I think
>>>>you're asking about latency. Looks like yours is about 268ms, using some
>>>>simplifying assumptions (speed of light in fiber at around 2/3 vacuum =
>>>>200000 km/s, no latency in telco equipment), this means that the network
>>>>distance from New York to Manila is about 33000 - 34000 miles. Seems a
>>>>bit
>>>>long for a planet with a 24000 mi diameter, unless you're going the long
>>>>way 'round.
>>>
>>>No kidding, the air distance is about 8500 miles. 1/4 second sounds
>>>about right for a geosync satellite hop. It's hard to imagine why
>>>you'd get a satellite link with the glut of fiber, but it should be
>>>easy enough to ask.

>>
>>Got a correction from
>>
>>
>>>Kirjoitit ryhmässä comp.dcom.sys.cisco:
>>>
>>>You need to divide that with two, ping time is RTT. So infact
>>>it's network distance to new york to manila to new york.
>>>
>>>HTH,
>>>--
>>> ++ytti

>>
>>I was wrong, and this is correct, so the "network distance" is really
>>16500 - 17000 miles. Or about twice the actual distance, so it still
>>sounds a bit slow. Do you have engineering documents from your carrier?
>>They might have some hints.
>>
>>

>
>
> Hi all:
>
> Thanks for the fascinating information. I could ask the carrier to see
> what they have. Is there something specific that I can ask from them
> or just a broad question?
>
> Maybe I should set up an ftp server on the US or Manila side and
> do around 10-20 ftp sessions and average out the result to find the
> "real" speed.
>
> How about that?
>
> TIA.
>
> John.
>
>

I would suggest the iperf utility instead of ftp for testing throughput.
 
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