Re: CEP vs Inverse Multiplexing

Discussion in 'Cisco' started by Andre Beck, Nov 21, 2003.

  1. Andre Beck

    Andre Beck Guest

    "SysAdmin" <> writes:
    >
    > Regarding the configuration of bundling multiple T1's to achieve a
    > higher throughput rate...
    >
    > Is CEP okay for this?


    What does the Cisco Certificate Enrollment Protocol have to do with it?
    Either I'm off here, or you wanted to write CEF.

    > I understand that Inverse Multiplexing is the
    > ultimate way to do it (inside the CSU instead of the router)


    This would require all T1s/E1s to be octet synchronous, which isn't
    achieved as easily as it seems. At least not if the carrier doesn't
    want it.

    > but looking for an ISP to provide that I am coming up short. Everyone
    > seems to want to offer the CEP solution which I believe is per-packet
    > load-balancing.


    There is indeed CEF per-packet load balancing. It has the big advantage
    of beeing the least CPU sucking method of bundling available (except from
    indeed inverse muxing with external hardware) and is thus prefered by ISPs
    over other solutions. External hardware costs extra and is likely incom-
    patible with aggregation solutions already in use by ISPs, so they will
    not support it until they already have the hardware to do it.

    > Isn't CEP really just an aggregate bandwidth and not really "real"?


    Depends on what you call real. The big disadvantage of any equal-distance
    load sharing is that it doesn't deal correctly with all sorts of traffic.
    For instance, IP multicast will not load share on a CEF per-packet bundle.
    Another problem is, it can reorder packets. While packet reorder is a
    normal thing in the IP world and L4+ are there to deal with it, nobody
    says that the dealing with it is as efficient as not having to deal with
    it. With certain L4+, it can create significant loss of throughput as
    well as increased traffic due to packet retransmissions. So better avoid
    it.

    As long as no real physical (probably external) mux/demux is available,
    the software thing closest to that is MP. The disadvantage of MP is that
    ISPs don't like it, some just out of attitude┬╣, some because it eats more
    CPU than CEF per-packet.

    ┬╣) You know, those who also refuse to run PPP and explain you how much
    more efficient Cisco HDLC would be.
    --
    The _S_anta _C_laus _O_peration
    or "how to turn a complete illusion into a neverending money source"

    -> Andre "ABPSoft" Beck +++ ABP-RIPE +++ Dresden, Germany, Spacetime <-
    Andre Beck, Nov 21, 2003
    #1
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