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How Fast is a T1? really.

 
 
john
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Posts: n/a
 
      11-29-2004
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!.



 
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Erik Freitag
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Posts: n/a
 
      11-29-2004
On Sun, 28 Nov 2004 21:06:03 -0500, 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!.


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. So there's probably a bit more latency in the network hardware
than 0, or your carrier's equipment or your own network is a bit slow.

The point is that latency is basically distance sensitive, not bandwidth
sensitive. A circuit running at or near capacity may have longer latency
than the same circuit running at low utilization, but that circuit has a
minimum latency determined by distance and equipment. As long as you're
running over fiber or copper, you're limited by the 200000 km/s number.

You're question caused me to do an Internet search on comparative T1
latencies for different carriers and distances. I could not find a good
reference. I would appreciate a pointer if anyone has one (also for T3).

 
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John R. Levine
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Posts: n/a
 
      11-29-2004
>> 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.


 
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Erik Freitag
Guest
Posts: n/a
 
      11-29-2004
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.


 
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john
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Posts: n/a
 
      11-29-2004

"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.


 
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Scooby
Guest
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.
> >
> >

>
> 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.
>
>


My first assumption was that this must be an internet T1 with VPN. However,
reading again it seems like you have installed a private T1??? I would
think that would be a very expensive proposition. If so, first check the
throughput on the circuit. If it is being heavily utilized, then you would
see higher ping times - QOS would probably fix this. If there is low
traffic, check with your telco to see what they have for an SLA. I'd assume
that they would be surprised to hear these results and you should
troubleshoot together with them to figure out where the problem is - it
could be your equipment.

One consideration is - what else are your routers doing? While 2600's (even
the older models) are plenty of router to handle a full T1, if it has too
many other things it is doing, it could degrade your system performance.

BTW - FTP tests will not show usability for IP Telephony, although they
might signal other bigger problems. Since TCP is just happy to have the
packets arrive in any order with high latencies, what you are experiencing
may not affect the transfer much - some, but not a lot. On the other hand,
such high latency with IP Telephony would cause serious jitter. Even with
QOS, the calls are likely to be very poor quality given your current
situation. Throughput and latency are very different issues.

An interesting/funny article for the Shark Tank fans out there:

http://www.computerworld.com/departm...,97552,00.html







 
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Erik Freitag
Guest
Posts: n/a
 
      11-29-2004
On Mon, 29 Nov 2004 08:51:29 -0500, john wrote:

>> 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?
>


If you're asking about latency, you might ask if they have a latency
guarantee for this T1. Loading up the circuit with a lot of ftp sessions
will tell you how bad the latency can get (it will go up as you congest
the circuit), but it will never go below the minimum for the circuit,
which looks to be about 268 ms (or 134 ms one-way).

You could ask them for their network documentation - somewhere, deep in
the archives, they have a text document or drawing (or set of them) that
shows each leg of the T1, and the equipment at each end. You can also ask
them to test the T1, but NOCs are usually only set up to check
connectivity and clocking, not latency - if that's what you're worried
about.

One of the carriers I've worked with guaranteed 80 ms for continental US
Internet traffic as long as it stayed on their network, and I think 100 ms
for traffic within western europe. They had no guarantee latency between
US/Europe (or US/Asia/Pacific).

> 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.


If you're talking about loading the T1 to see whether you're really
getting a full T1 worth of bandwidth, the ftp test might work. You could
also just change your router interface load-interval to 30 seconds and
start a lot (5-6) of largish (1000 byte) 100000 packet ping sessions. Do a
couple of show interface commands while the sessions are running and see
if you get to 1500000 bits/second or so. This is closer to testing just
the T1. If you use ftp, you're also testing your servers, their disks, and
the internal network leading up to the T1.

 
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T. Sean Weintz
Guest
Posts: n/a
 
      11-29-2004
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.

 
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Toby
Guest
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
Guest
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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