voip calls using cisco

Discussion in 'VOIP' started by tease12p, Jul 11, 2003.

  1. tease12p

    tease12p Guest

    hi
    i have a question..
    in order to place a VOIP call and actually achieve very good quality,
    is it necessary to use RSVP based resource reservation?? what is the
    normal way in which a VOIP call is treated in any IP network?
    Does Cisco make use of rsvp mandatory?
    are there any other companies that make VoIP gateways?
    thanks
    t
     
    tease12p, Jul 11, 2003
    #1
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  2. tease12p

    shope Guest

    "shido" <> wrote in message
    news:8gCPa.4887$...
    > You might want to take a look at www.asterisk.org.


    Sort of OT...
    >
    > -Greg
    >
    > "tease12p" <> wrote in message
    > news:...
    > > hi
    > > i have a question..
    > > in order to place a VOIP call and actually achieve very good quality,
    > > is it necessary to use RSVP based resource reservation??


    No - its necessary to have enough bandwidth available for the call, and
    latency and drop %age to suit the call quality required.

    Many private networks have Voip added using simple priority schemes - but
    you need to be able to limit the amount of voip traffic to avoid starving
    others uses of the bandwidth of service. Some IP Telephony systems have ways
    to limit numbers of calls or amount of bandwidth over particular paths - or
    you limit the number of calls within the design.

    If there is just one path with limited bandwidth, then limiting the codec
    type and number of calls is enough. More complex topologies benefit more
    from RSVP, since you reserve bandwidth for calls in progress, and you can
    load balance the usage and so on.

    RSVP is not ideal - many WAN links are low bandwidth and use compression,
    and since RSVP works at layer 3 and header / IP / link layer compression may
    be "inivisble" to Voip, the reservations sometimes dont correspond to
    bandwidth actually used.

    what is the
    > > normal way in which a VOIP call is treated in any IP network?


    It depends. In a LAN it is usually "so much bandwidth" that voip just gets
    absolute priority. Or if the LAN runs at low load ignore priorty all
    together - it can work (until something in the traffic profile changes).

    The more complex schemes tend to get used where bandwidth is scarce - the
    payback is worth the complexity.

    > > Does Cisco make use of rsvp mandatory?


    No.

    > > are there any other companies that make VoIP gateways?
    > > thanks


    Loads - but compatibility is voip / IP Telephony is not a given. You need
    compatible codecs, signalling, and sometimes more subtle stuff still gets in
    the way.

    > > t

    >

    --
    Regards

    Stephen Hope - remove xx from email to reply
     
    shope, Jul 11, 2003
    #2
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