T1 aggregation limitations

Discussion in 'Cisco' started by Xophry K'un Le'im, Apr 28, 2006.

  1. Hello,

    I want to use a pair of Cisco 2821 routers, each with 3 WICS
    (VWIC2-2MFT-T1/E1) connecting a total of 6 T1 lines to create a 9Mbs
    point-to-point link between two offices.

    I want all lines to be load balanced so that any user could potentially
    use most of the bandwidth.

    My understanding is that I can use CEF and enable ip load-sharing
    per-packet on each interface in order to accomplish this.

    Can anyone confirm, based on experience, that this is a sound plan?

    If this basic idea is sound, what options are available for setting
    priorties by MAC or Client IP address or otherwise limiting/controlling
    the burst rates?

    Multilink PPP seems to load-balance based on IP address, and therefore,
    if my understanding is correct, no ip conversation would be capable of
    exceeding 1.5Mbs. Is this correct?

    I appreciate any assistance you can offer.

    Xophry
     
    Xophry K'un Le'im, Apr 28, 2006
    #1
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  2. Xophry K'un Le'im

    Wayne Guest

    "Xophry K'un Le'im" <> wrote in message
    news:...
    > Hello,
    >
    > I want to use a pair of Cisco 2821 routers, each with 3 WICS
    > (VWIC2-2MFT-T1/E1) connecting a total of 6 T1 lines to create a 9Mbs
    > point-to-point link between two offices.
    >
    > I want all lines to be load balanced so that any user could potentially
    > use most of the bandwidth.
    >
    > My understanding is that I can use CEF and enable ip load-sharing
    > per-packet on each interface in order to accomplish this.
    >
    > Can anyone confirm, based on experience, that this is a sound plan?
    >
    > If this basic idea is sound, what options are available for setting
    > priorties by MAC or Client IP address or otherwise limiting/controlling
    > the burst rates?
    >
    > Multilink PPP seems to load-balance based on IP address, and therefore,
    > if my understanding is correct, no ip conversation would be capable of
    > exceeding 1.5Mbs. Is this correct?
    >
    > I appreciate any assistance you can offer.
    >
    > Xophry
    >


    Multilink PPP is the way to go. One flow can use the entire pipe with MLPPP
    and the load balancing is almost perfect.

    Got to ask the question though, for a 9 mbps link, have you looked into a
    MetroE or MPLS connection instead traditional T1s?
     
    Wayne, Apr 28, 2006
    #2
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  3. Xophry K'un Le'im

    Guest

    > Multilink PPP seems to load-balance based on IP address, and > therefore,

    No it doesn't.

    For N lines it divides _each_ packet into N pieces
    and sends one piece down each line.

    Sucks up a lot of CPU. Maybe a 2821 will do though.

    Would want some test numbers.
     
    , Apr 28, 2006
    #3
  4. We use PPP Multilink in our network. We have 4 sites that use multilink
    bundles ranging from 5 to 7 T1s. We are using 2620 routesr on most of
    these links, and it does make the CPU work hard. During peak traffic
    times, the CPU goes to 75%, most of which is interrupt processing.

    We have 1 2650XM that, under the same traffic loads, goes only to about
    25%.
     
    Mark Williams, Apr 28, 2006
    #4
  5. Ok, so Multilink PPP is not as limited as I thought.

    Regarding traffic shaping/bandwidth allocation...

    I have a mission crictical database application that will require 40%
    of the bandwidth if all current database users are bursting at the
    maximum rate simultaneously (rarely, if ever). Normal database traffic
    will average 15-20% of the total available bandwidth of the 6 T1 lines.

    Additionally, I need to support normal resource sharing traffic. I
    want the database application to be able to utilize 40 percent of the
    bandwidth if it needs it, and I want the resource sharing/network
    management to utilize up to 95 percent of the bandwidth, if it is not
    in use by the database application. The mission critical use of the
    database can be isolated to certain IP addresses. Though other IP
    addresses will require occassional database access, these ancillary
    workstations do not necessarily require high-priority database access.

    What is the best bandwidth management strategy for this? I was
    thinking that Class Based shaping would get me what I want, but this
    article does not indicate that this feature is available on the 2821
    and I can't seem to find the correct documentation to answer my
    question.
    http://www.cisco.com/univercd/cc/td...s121/121newft/121t/121t2/clsbsshp.htm#1026464


    Thoughts?
     
    Xophry K'un Le'im, Apr 28, 2006
    #5
  6. Xophry K'un Le'im

    jay Guest

    Hi,
    CBWFQ is actually avaliable on the ISR's (i.e2800).. and think its
    avaliable on the lowest avaliable feature set as well. Check the Cisco
    Tools page for the IOS feature navigator to be sure.
    It would work well for what your trying to achieve above. Ie. Reserving
    Bandwidth in the event of of planned bursty congestion. No good reason
    to use LLQ since little on no serialisation delay on a 9mb pipe.
     
    jay, Apr 30, 2006
    #6
  7. Thanks for the direction.
     
    Xophry K'un Le'im, May 3, 2006
    #7
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