What is your favorite method to troubleshoot high-bandwidth/high latency networks?

Discussion in 'Windows Networking' started by Spin, May 4, 2009.

  1. Spin

    Spin Guest

    Gurus,

    What is your favorite method to troubleshoot high-bandwidth/high latency
    networks? I know about the ping and telnet tests you can do, aside from
    getting on the phone with the ISP, is there anything one can do from the
    internal customer's side of the house in order to find the "smoking gun"?
     
    Spin, May 4, 2009
    #1
    1. Advertisements

  2. I always look at the network infrastructure design,...the "topology" if you
    want to call it that. Most of the time,..if they are designed correctly
    they work correctly. Most network problems that I run across are caused by
    the Admins and their bad designs. Of course the LAN and the WAN are two
    different things and have to be investigated separately.


    --
    Phillip Windell
    www.wandtv.com

    The views expressed, are my own and not those of my employer, or Microsoft,
    or anyone else associated with me, including my cats.
    -----------------------------------------------------
     
    Phillip Windell, May 4, 2009
    #2
    1. Advertisements

  3. Spin

    Spin Guest

    It's difficult to get Verizon, AT&T and other major ISP players to divulge
    their network infrastructure design and the type of equipment they use,
    though not impossible if your considered a top tier customer. Getting some
    engineer on the phone to help pinpoint an SLA problem is another story. I'm
    so tired of spending night son the phone with service providers only to find
    out the problem was caused by an admin or bad design. Happens a lot.
    That's why I'm looking to develop a little checklist of "smoking guns" to
    look for, a or at least put something together based on responses to this
    thread in this NG.
     
    Spin, May 4, 2009
    #3
  4. Yea,..that's why we use a local provider that I can hop in the car and drive
    over there and grab them by the shirt if I have to.
    Well,...it's like I said before. The Internet performance and the LAN
    performance have nothing to do with each other. The LAN can run perfectly
    fine without the Internet,...like they did before the Interent ever came
    along. By the same token the Internet connection can run perfectly fine
    without the LAN, like it does with a home user with one machine and no LAN.

    So you have to determine what it really is you are looking for. By your
    post,...I cannot tell what it is. Is the LAN slow? Is the Internet
    slow?,...they are not the same thing.

    --
    Phillip Windell
    www.wandtv.com

    The views expressed, are my own and not those of my employer, or Microsoft,
    or anyone else associated with me, including my cats.
    -----------------------------------------------------
     
    Phillip Windell, May 4, 2009
    #4
  5. Spin

    Spin Guest

    Well, consider the case of a dedicated site-to-site VPN, which is an
    Internet technology designed to make remote networks "look" local. In this
    case, we have a LAN which is really a WAN but made to look like a LAN.
    These are the case for which I speak.
     
    Spin, May 4, 2009
    #5
  6. In that case it is the Internet. The VPN Tunnel is not "real" it is an
    imaginary thing,...a "logical" thing. So they are just "packets" going over
    the Internet,..what is ecapsulated within them is not relevant. VPN by
    nature is slower than regular Internet traffic for two reasons:

    1. The required encapsulation and encryption has a cost in performance

    2. VPN runs Synchronous (same speed both ways), so if the Internet
    connection is Asynchronous (fast download, slow upload) then it is going to
    run at the slower "upload" speed of the connection minus the protocol
    overhead (mentioned in #1)and minus whatever bandwidth is already being used
    up by other things.

    So,...do some speed tests to see what you are dealing with. Anything less
    that about 1,200 mbps is going to perform like crap (IMO).

    One of the many speed test sites is http://www.speakeasy.net/speedtest

    The next important thing to remember is that there are *two* Internet
    connections involved with VPN,...one at each end,...it only takes one of
    them to screw it up. It is only going to run at the slowest speed of the
    slowest connection, minus the other bandwidth eating factors mentioned
    above.

    --
    Phillip Windell
    www.wandtv.com

    The views expressed, are my own and not those of my employer, or Microsoft,
    or anyone else associated with me, including my cats.
    -----------------------------------------------------
     
    Phillip Windell, May 4, 2009
    #6
  7. Spin

    Spin Guest

    How would I test the speed between two buildings which are in two
    geographically separate cities in my site-to-site VPN network?
     
    Spin, May 5, 2009
    #7
  8. Hello,

    Bandwidth perf: iperf (open source)
    Latency: smokeping (open source)

    just my 2 cents,

    Spin a écrit :
     
    Mathieu CHATEAU, May 5, 2009
    #8
  9. Copy a file between the two and time it. Then do the math against the file
    size.

    Just remember that the file size is in Bytes and the bandwidth speed is in
    Bits,...it takes 8 Bits to make a Byte.

    So 100 mbps (bits) of line speed = 12.5 MBps (bytes)

    So a file that is 25meg in size (bytes) should take two seconds over a 100
    mbps line if the whole line's bandwidth is dedicated to the task. But in
    "real life" nothing ever max's out the line during a transfer,...there is
    *always* some left over bandwidth,...so it would really take more than two
    seconds. Remember that if something used all the bandwidth for a single
    action then only one thing (user?) could ever use the Line at one
    time,...and we know that this is not how it works out in real
    life,...multiple things happen over the line at the same time. So in the
    end all you are going to get is a general idea of how well it is doing.

    Anyone is welcomed to correct my "math" if I screwed it up. I tend to "poke
    and eye out" with math if I'm not careful.


    --
    Phillip Windell
    www.wandtv.com

    The views expressed, are my own and not those of my employer, or Microsoft,
    or anyone else associated with me, including my cats.
    -----------------------------------------------------
     
    Phillip Windell, May 5, 2009
    #9
  10. Also keep in mind that Bandwidth is not the speed.
    Thoughput is the speed.

    To give a physical illustration of this:

    Bandwidth = the number of lanes on a road moving in the same direction

    Throughput = the speed limit that the road runs at

    So a two lane road can move twice and many cars in the same amount of
    time,...but both cars still move at the same speed. So if the road has two
    lanes (same direction) with a 60mph limit, it does not mean that if there is
    only one car on the road it can run a 120mph.

    --
    Phillip Windell
    www.wandtv.com

    The views expressed, are my own and not those of my employer, or Microsoft,
    or anyone else associated with me, including my cats.
    -----------------------------------------------------
     
    Phillip Windell, May 5, 2009
    #10
  11. Spin

    Spin Guest

    And latency = heavy traffic / slow speeds.
     
    Spin, May 5, 2009
    #11
  12. That would be packet delay (excessive transit time).

    Latency is a "processing" thing. It is the time it takes for the packet to
    be processed by a particular networking device before the packet is actually
    dropped on the wire. So it would be like a car having to wait at a Red
    Light before it can pull out onto the two-lane road. The primary cause of
    Latency is too many LAN Routers or two many Switches between the end points
    (too many traffic lights),...add the processing time of all the devices
    together that is passes through and that is your latency time. A faulty or
    over loaded Router or Switch can casue a spike in the latency. Another
    example is the Application being used by the user taking too long, for
    whatever reason, before it begins to communicate with whatever it
    communicates with.


    --
    Phillip Windell
    www.wandtv.com

    The views expressed, are my own and not those of my employer, or Microsoft,
    or anyone else associated with me, including my cats.
    -----------------------------------------------------
     
    Phillip Windell, May 6, 2009
    #12
  13. latency is also the time needed for a packet to go from earth to the
    satellite

    also for the packet to go through the atlantic. Even fiber goes half the
    speed of the light i think, so it needs some time under sea



    Phillip Windell a écrit :
     
    Mathieu CHATEAU, May 6, 2009
    #13
  14. Years back when I went for my CCNA, Cisco was adament that these two things
    were Lag-Time and Delay and specifically not Latency. It all seems like
    splitting hairs and word-play to me,...but if we didn't answer it right, we
    were counted wrong.

    It was called Lag Time with the Satelite and was Delay (or Packet Delay, or
    Transit Delay) when running over a long cable. With the Satelite the
    Latency was the lost time between the Transceiver receiving the packet and
    when it sent the packet up,...the second Latency was the time lost between
    the Satelite receiving the packet and resending the packet back down,...and
    then again at the Tranceiver at the end.

    Anyway to me sometimes it is just splitting hairs, but we had to keep it
    straight for the exams. I do though try to use proper terminology as best I
    know to do since the IT industry is already in a "terminology crisis" over
    misused and abused terminology, particularly since the growth of "home user
    networking". Examples of that are calling cheap SOHO NAT-Firewalls
    "routers" when they are not routers,...and inventing the term "port
    forwarding" when the ports are not even the focus of the "action",..it's
    really a focus on the IP# and the process is primarily a Layer3 process, not
    a Layer4 process, and the real name that has long since been establish for
    the process by the industry for years is "Static NAT" or "Reverse-NAT".
    There was never a need to invent a new "word".

    --
    Phillip Windell
    www.wandtv.com

    The views expressed, are my own and not those of my employer, or Microsoft,
    or anyone else associated with me, including my cats.
    -----------------------------------------------------
     
    Phillip Windell, May 7, 2009
    #14
  15. Spin

    Dave Warren Guest

    In message <> "Phillip Windell"
    And "DMZ" -- What a bastardization of concepts that one is, since what
    most SOHO gear calls a DMZ is all but the opposite of a real DMZ.
     
    Dave Warren, May 7, 2009
    #15
  16. AH! Yea!! I forgot about that one! I think that one is from Linksys. I
    think what it really is, is a 1:1 NAT directly to whatever IP you tell it.
    How in the world they ever came up with DMZ for that one!?! It is almost
    like they just grab a "popular" word off the shelf and just use it for
    whatever trips their trigger regaurdless of what it really means.

    What couldn't they just "make up" a new word!?!,....like a
    "dischronificator address" of something instead of a term that already has
    an establshed meaning,....of course I'd still complain about that too...

    The really sad thing is that they were bought by Cisco,...who is highly
    responsible for the proper meaning of a lot of industry terminology,...yet
    they have not even attempted to correct that blatant non-sense. What's
    wrong with them?,..they asleep?

    --
    Phillip Windell
    www.wandtv.com

    The views expressed, are my own and not those of my employer, or Microsoft,
    or anyone else associated with me, including my cats.
    -----------------------------------------------------
     
    Phillip Windell, May 7, 2009
    #16
    1. Advertisements

Ask a Question

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

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.