Networking Question

Discussion in 'Cisco' started by seijin@gmail.com, Feb 27, 2008.

  1. Guest

    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!
     
    , Feb 27, 2008
    #1
    1. Advertising

  2. Trendkill Guest

    On Feb 27, 4:50 pm, 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.
     
    Trendkill, Feb 27, 2008
    #2
    1. Advertising

  3. Thrill5 Guest

    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" <> wrote in message
    news:...
    > On Feb 27, 4:50 pm, 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.
     
    Thrill5, Feb 28, 2008
    #3
  4. Merv Guest

    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.
     
    Merv, Feb 28, 2008
    #4
  5. Houston SBC Guest

    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

    <> wrote in message
    news:...
    > 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!
    >
     
    Houston SBC, Mar 3, 2008
    #5
  6. Guest

    On Mar 3, 4:35 am, "Houston SBC" <>
    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
    >
    > <> wrote in message
    >
    > news:...
    >
    > > 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.
     
    , Mar 5, 2008
    #6
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Eddy Malik [MSFT]
    Replies:
    0
    Views:
    871
    Eddy Malik [MSFT]
    Mar 22, 2005
  2. =?Utf-8?B?QUJTUE9QVVA=?=

    PROBLEMS WITH NETWORKING - NEW TO NETWORKING

    =?Utf-8?B?QUJTUE9QVVA=?=, Mar 22, 2005, in forum: Wireless Networking
    Replies:
    2
    Views:
    643
    =?Utf-8?B?QUJTUE9QVVA=?=
    Mar 23, 2005
  3. barry crowley
    Replies:
    20
    Views:
    1,302
  4. Andy
    Replies:
    4
    Views:
    883
  5. elie
    Replies:
    0
    Views:
    1,029
Loading...

Share This Page