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Networking Question

 
 
seijin@gmail.com
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Posts: n/a
 
      02-27-2008
Hi,

I have a question on network optimization. I work at a company that
has a corporate office. Our local division has a T1 and VPN through
the AT&T network. We have Cisco routers and switches. The router is
a 2811 and I believe the switches are 2950. Our corporate office is
supposed to handle the major networking issues so I'm limited with
what I can actually do.

We experience two issues. Our main issue is response time from a
telnet application. This application is used by everyone and is
critical to our work environment. Not critical as in "We lose money/
people die every time this thing slows down" but it's a major concern
whenever the thing lags. And it does lag throughout the day.

The server hosting the application is at our corporate office. Our
Exchange server is also at the corporate office.

The telnet app would periodically lag horribly throughout the day.
When it's working well you can type with a barely noticeable delay.
When it's bad, you're typing a bit and then waiting for it to catch
up. We complained but our corporate network guy said we weren't even
using our full T1 line. So, I did a a little investigation during two
verified lag time periods and found that our response times can go
from 40 ms to 450+ ms when things are bad. For example, a user
running a program that needs to grab large bits of information from
the Internet. I guess whatever report they run shows our bandwidth is
fine but telnet is sensitive.

Is there anything we can do? I'd thought we'd be able to set some
policies on the router that would throttle Internet traffic in favor
of telnet traffic but the corporate office (supposedly) tried this and
the users still complained at response times. Well, that and websites
timing out left and right.

Advice, please!
 
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Trendkill
Guest
Posts: n/a
 
      02-27-2008
On Feb 27, 4:50 pm, (E-Mail Removed) wrote:
> Hi,
>
> I have a question on network optimization. I work at a company that
> has a corporate office. Our local division has a T1 and VPN through
> the AT&T network. We have Cisco routers and switches. The router is
> a 2811 and I believe the switches are 2950. Our corporate office is
> supposed to handle the major networking issues so I'm limited with
> what I can actually do.
>
> We experience two issues. Our main issue is response time from a
> telnet application. This application is used by everyone and is
> critical to our work environment. Not critical as in "We lose money/
> people die every time this thing slows down" but it's a major concern
> whenever the thing lags. And it does lag throughout the day.
>
> The server hosting the application is at our corporate office. Our
> Exchange server is also at the corporate office.
>
> The telnet app would periodically lag horribly throughout the day.
> When it's working well you can type with a barely noticeable delay.
> When it's bad, you're typing a bit and then waiting for it to catch
> up. We complained but our corporate network guy said we weren't even
> using our full T1 line. So, I did a a little investigation during two
> verified lag time periods and found that our response times can go
> from 40 ms to 450+ ms when things are bad. For example, a user
> running a program that needs to grab large bits of information from
> the Internet. I guess whatever report they run shows our bandwidth is
> fine but telnet is sensitive.
>
> Is there anything we can do? I'd thought we'd be able to set some
> policies on the router that would throttle Internet traffic in favor
> of telnet traffic but the corporate office (supposedly) tried this and
> the users still complained at response times. Well, that and websites
> timing out left and right.
>
> Advice, please!


Three things:
A) Make sure your network guy is watching the bandwidth (at a close
interval) via something like mrtg or netflow, and try to figure out if
the response times correspond with high bandwidth utilization. If so,
consider bucketing or throttling your big traffic users (I'd have to
guess email/outlook if your server is remote from your location), but
would also keep an eye out for internet or ftp traffic.
B) Look at QoS to help either prioritize certain traffic (telnet), or
limit the usage of your heavy hitter applications. This can be done
by source, destination, network, port, etc. Your network engineer
should be able to help here.
C) If bandwidth doesn't appear to be the issue, you need to escalate
with your provider. If your latency is going to 400+ms and is not
related to your usage, then there is no excuse from the provider.

One last thing, are you using the VPN over the t1? If so, why? Is
the t1 to the internet (then it would make sense), or is it private?
Either way the VPN should not add too much processing or latency to a
single t1, but something to watch since you only have a 2811. Again,
I don't suspect this, but something to keep in mind.
 
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Thrill5
Guest
Posts: n/a
 
      02-28-2008
You need to implement QoS on the router. Create three queues, high, medium
and scavenger. Place your telnet application in the high queue, your VPN
traffic (any traffic that is destined for the corporate office) into the
medium queue, and your internet traffic (everything else) into the scavenger
queue. Telnet is not high bandwidth, so allocate the minimum bandwidth (5%
or 64k or something like that), 65% to the medium, and the rest to scavenger
(or any other numbers that you think are appropriate.) The bandwidth
numbers only count when you have congestion, and even if you have
congestion, any bandwidth that is not used by the queues can be used by the
others if they have exceeded their allocation. If you still have "slowness"
with telnet after implementation, you may have to change the "high" queue to
a priority queue, but I doubt this since you have a T1. With a priority
queue, any traffic in that queue is ALWAYS sent before any other traffic and
the bandwidth you allocate to it will ONLY be used for the priority queue.
So if you allocate 64K, that bandwidth is always reserved even if you don't
have any priority traffic. Priority queues are generally only used for
voice traffic where jitter is problem.


"Trendkill" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> On Feb 27, 4:50 pm, (E-Mail Removed) wrote:
>> Hi,
>>
>> I have a question on network optimization. I work at a company that
>> has a corporate office. Our local division has a T1 and VPN through
>> the AT&T network. We have Cisco routers and switches. The router is
>> a 2811 and I believe the switches are 2950. Our corporate office is
>> supposed to handle the major networking issues so I'm limited with
>> what I can actually do.
>>
>> We experience two issues. Our main issue is response time from a
>> telnet application. This application is used by everyone and is
>> critical to our work environment. Not critical as in "We lose money/
>> people die every time this thing slows down" but it's a major concern
>> whenever the thing lags. And it does lag throughout the day.
>>
>> The server hosting the application is at our corporate office. Our
>> Exchange server is also at the corporate office.
>>
>> The telnet app would periodically lag horribly throughout the day.
>> When it's working well you can type with a barely noticeable delay.
>> When it's bad, you're typing a bit and then waiting for it to catch
>> up. We complained but our corporate network guy said we weren't even
>> using our full T1 line. So, I did a a little investigation during two
>> verified lag time periods and found that our response times can go
>> from 40 ms to 450+ ms when things are bad. For example, a user
>> running a program that needs to grab large bits of information from
>> the Internet. I guess whatever report they run shows our bandwidth is
>> fine but telnet is sensitive.
>>
>> Is there anything we can do? I'd thought we'd be able to set some
>> policies on the router that would throttle Internet traffic in favor
>> of telnet traffic but the corporate office (supposedly) tried this and
>> the users still complained at response times. Well, that and websites
>> timing out left and right.
>>
>> Advice, please!

>
> Three things:
> A) Make sure your network guy is watching the bandwidth (at a close
> interval) via something like mrtg or netflow, and try to figure out if
> the response times correspond with high bandwidth utilization. If so,
> consider bucketing or throttling your big traffic users (I'd have to
> guess email/outlook if your server is remote from your location), but
> would also keep an eye out for internet or ftp traffic.
> B) Look at QoS to help either prioritize certain traffic (telnet), or
> limit the usage of your heavy hitter applications. This can be done
> by source, destination, network, port, etc. Your network engineer
> should be able to help here.
> C) If bandwidth doesn't appear to be the issue, you need to escalate
> with your provider. If your latency is going to 400+ms and is not
> related to your usage, then there is no excuse from the provider.
>
> One last thing, are you using the VPN over the t1? If so, why? Is
> the t1 to the internet (then it would make sense), or is it private?
> Either way the VPN should not add too much processing or latency to a
> single t1, but something to watch since you only have a 2811. Again,
> I don't suspect this, but something to keep in mind.



 
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Merv
Guest
Posts: n/a
 
      02-28-2008
Telnet can send one character at a time unless the TCP stack supports
the Nagle algorithm and that it is enabled.

for example Windows Sockets applications can disable the Nagle
algorithm for their connections by setting the TCP_NODELAY socket
option. Also tuning server TCP stacks may help.

You could load WireShark (free packet sniffer) onto one of the PC used
for the telnet application and capture a session to see how many
characters are being packed into each outbound packet.
 
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Houston SBC
Guest
Posts: n/a
 
      03-03-2008
This may be "bit bucket delay" if AT&T has you on a frame relay circuit.
Are the sites geographically distant?
Telnet will drive users crazy if the RTT (Round Trip Time) is over 100mS
and frame relay is known for this problem (so is Satellite).
If the T-1 is using Frame then look at the CIR (Committed Information Rate),
BIR (Burst Information Rate), and any guarantees on the RTT. The config on
your Cisco 2811 will indicate if frame is in use on the link to your router.
Nonetheless, Frame Relay could be in use further down the link---the
providers are very good at using the least cost link and Frame is cheap and
very susceptible to over-subscription causing the large discrepancies you
see in RTTs. Hold their feet to the fire on any Service Level Agreement in
place.

When you say T-1 with VPN through the AT&T network--this sounds as though
your traffic is transported across the Internet (else why the VPN?). In case
the VPN is in place due to your data travelling across the Internet--you
have no control
since the Internet has no QOS guarantees, and I would expect slowdowns in
the 10 to noon and 1-3 pm local time frames with peaks at 10 am and 2 pm.

Nonetheless, if your users are using a significant portion of the available
bandwidth--increase your bandwidth...No free lunch..

Doug Stigall
Sys Analyst
Digital Machines Corp.
Doug@!@noSpam. DMCTX.com

rEmove !@noSpam. to reply

<(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Hi,
>
> I have a question on network optimization. I work at a company that
> has a corporate office. Our local division has a T1 and VPN through
> the AT&T network. We have Cisco routers and switches. The router is
> a 2811 and I believe the switches are 2950. Our corporate office is
> supposed to handle the major networking issues so I'm limited with
> what I can actually do.
>
> We experience two issues. Our main issue is response time from a
> telnet application. This application is used by everyone and is
> critical to our work environment. Not critical as in "We lose money/
> people die every time this thing slows down" but it's a major concern
> whenever the thing lags. And it does lag throughout the day.
>
> The server hosting the application is at our corporate office. Our
> Exchange server is also at the corporate office.
>
> The telnet app would periodically lag horribly throughout the day.
> When it's working well you can type with a barely noticeable delay.
> When it's bad, you're typing a bit and then waiting for it to catch
> up. We complained but our corporate network guy said we weren't even
> using our full T1 line. So, I did a a little investigation during two
> verified lag time periods and found that our response times can go
> from 40 ms to 450+ ms when things are bad. For example, a user
> running a program that needs to grab large bits of information from
> the Internet. I guess whatever report they run shows our bandwidth is
> fine but telnet is sensitive.
>
> Is there anything we can do? I'd thought we'd be able to set some
> policies on the router that would throttle Internet traffic in favor
> of telnet traffic but the corporate office (supposedly) tried this and
> the users still complained at response times. Well, that and websites
> timing out left and right.
>
> Advice, please!
>



 
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seijin@gmail.com
Guest
Posts: n/a
 
      03-05-2008
On Mar 3, 4:35 am, "Houston SBC" <(E-Mail Removed)>
wrote:
> This may be "bit bucket delay" if AT&T has you on a frame relay circuit.
> Are the sites geographically distant?
> Telnet will drive users crazy if the RTT (Round Trip Time) is over 100mS
> and frame relay is known for this problem (so is Satellite).
> If the T-1 is using Frame then look at the CIR (Committed Information Rate),
> BIR (Burst Information Rate), and any guarantees on the RTT. The config on
> your Cisco 2811 will indicate if frame is in use on the link to your router.
> Nonetheless, Frame Relay could be in use further down the link---the
> providers are very good at using the least cost link and Frame is cheap and
> very susceptible to over-subscription causing the large discrepancies you
> see in RTTs. Hold their feet to the fire on any Service Level Agreement in
> place.
>
> When you say T-1 with VPN through the AT&T network--this sounds as though
> your traffic is transported across the Internet (else why the VPN?). In case
> the VPN is in place due to your data travelling across the Internet--you
> have no control
> since the Internet has no QOS guarantees, and I would expect slowdowns in
> the 10 to noon and 1-3 pm local time frames with peaks at 10 am and 2 pm.
>
> Nonetheless, if your users are using a significant portion of the available
> bandwidth--increase your bandwidth...No free lunch..
>
> Doug Stigall
> Sys Analyst
> Digital Machines Corp.
> Doug@!@noSpam. DMCTX.com
>
> rEmove !@noSpam. to reply
>
> <(E-Mail Removed)> wrote in message
>
> news:(E-Mail Removed)...
>
> > Hi,

>
> > I have a question on network optimization. I work at a company that
> > has a corporate office. Our local division has a T1 and VPN through
> > the AT&T network. We have Cisco routers and switches. The router is
> > a 2811 and I believe the switches are 2950. Our corporate office is
> > supposed to handle the major networking issues so I'm limited with
> > what I can actually do.

>
> > We experience two issues. Our main issue is response time from a
> > telnet application. This application is used by everyone and is
> > critical to our work environment. Not critical as in "We lose money/
> > people die every time this thing slows down" but it's a major concern
> > whenever the thing lags. And it does lag throughout the day.

>
> > The server hosting the application is at our corporate office. Our
> > Exchange server is also at the corporate office.

>
> > The telnet app would periodically lag horribly throughout the day.
> > When it's working well you can type with a barely noticeable delay.
> > When it's bad, you're typing a bit and then waiting for it to catch
> > up. We complained but our corporate network guy said we weren't even
> > using our full T1 line. So, I did a a little investigation during two
> > verified lag time periods and found that our response times can go
> > from 40 ms to 450+ ms when things are bad. For example, a user
> > running a program that needs to grab large bits of information from
> > the Internet. I guess whatever report they run shows our bandwidth is
> > fine but telnet is sensitive.

>
> > Is there anything we can do? I'd thought we'd be able to set some
> > policies on the router that would throttle Internet traffic in favor
> > of telnet traffic but the corporate office (supposedly) tried this and
> > the users still complained at response times. Well, that and websites
> > timing out left and right.

>
> > Advice, please!


Thank you all for the replies.

Can a 2800 series Cisco router do priority queueing such as high-
medium-low? The network guy at our corporate office supposedly
implemented QoS but not I'm not sure to what level. I've had
conflicting reports as to what he's tried. I'll send him a message to
see if I can find out exactly what he tried. I do have one email
where he's said that "... policing HTTP to limit it to 20% of the T1
at the serial interface, inbound."

Here's a little more (clearer, hopefully) information on our setup.
We have a T1 at our site through AT&T. I believe we're using MPLS and
have a VPN connection to the corporate office as well as our sister
offices. We also have Citrix for some applications (hosted at the
corporate office) and our Exchange servers are hosted at the corporate
office. The server we're connecting to via telnet is at the corporate
office and is accessed through that VPN connection. I checked with
Wire Shark and it doesn't seem like the telnet app is sending one byte
at a time. The several times I've had a user say "The telnet app is
slow!" I've gone in and checked - bandwidth usage spikes and so does
response time. Due to Internet traffic and possibly high Exchange
server traffic at that moment.

Our corporate office says we aren't using the full bandwidth of our T1
but I think that we're seeing slow response time because of sudden
spikes. I think that policy on HTTP traffic may be the only policy
that was put into place and then we had users complain of the telnet
app being slow AND Internet traffic being slow. So I'm thinking it's
not just HTTP traffic causing the problem.

We have some web tools that show bandwidth usage and another tool that
shows response times on the T1 line so I think I'll need to look at
both and identify what app(s) are causing response times to go too
high.
 
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