Re: Cisco 837 and 7Mbit ADSL Line

Discussion in 'Cisco' started by Stephen, Feb 26, 2011.

  1. Stephen

    Stephen Guest

    On Sat, 26 Feb 2011 11:28:46 +0100, "Elia S."
    <> wrote:

    >Hello
    >is a cisco 837 capable of using a 7mbit adsl line? (negotiated 8128 ADSL-1
    >type line)
    >

    raw thruput figures for IP forwarding:
    http://www.cisco.com/web/partners/downloads/765/tools/quickreference/routerperformance.pdf

    >I mean.. since that router does just NAT and nothing else, is the cpu
    >capable of transferring 7mbit down and 512k up?


    NAT takes some extra steps over simple IP forwarding, so may not reach
    these numbers - but you have a bit of headroom

    note the perf is usually measured on Ethernet ports - that gives the
    minimum overhead, so driving the ADSL line may cause an issue.
    >
    >thank you


    good luck
    --
    Regards

    - replace xyz with ntl
     
    Stephen, Feb 26, 2011
    #1
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  2. Stephen

    Stephen Guest

    On Sun, 27 Feb 2011 10:45:17 +0100, "Elia S."
    <> wrote:

    >Hello
    >just yesterday night I was doing some tests:
    >
    >I have on the same site, two different ADSL lines:
    >
    >1) 7M/512 - fast - negotiated 8128
    >2) 7M/512 - interleaved - negotiated 7616
    >
    >On line 1 I have a C2651XM with 12.4(25b) and WIC1-ADSL (rev C0)
    >on line 2 I have a c837 with 12.4(25b)
    >
    >From the same site, with wide bandwidth, I download:
    >
    >1) from the 2651xm , 690Kbyte/sec - (5,3bit) cpu 40%
    >2) from the c837 , 799Kbyte/sec (6,3mbit) - cpu 75%
    >
    >The configurations are exactly the same.
    >According to http://www.docstoc.com/docs/36024093/clock-rate I am pretty
    >sure that the 2651xm has some limitations in the wic bus. I have raised it
    >to 70000 but It seems to be unable to max-out a 7mbit line.


    The line speeds you have are before ATM overheads are allowed for.

    Depending on where you are, there may be some overhead on the line as
    different operators set up ADSL differently.

    However 7 Mbps with ATM overhead is at absolute best case 7 * 48/53
    (and then with some added packet header overhead).

    so around 6.3 Mbps, then you have Ethernet frame overhead in that.

    so item 2 is approx 6.4 Mbps, and that probably means the negotiated
    rate is a bit over 7 Mbps.

    WIC / WIC slots were limited to 8 Mbps - i suspect this was a bus
    limit for so ADSL may be input + output including internal overhead,
    so your 7 Mbps down / 512 up may be too much.
    http://www.cisco.com/web/partners/downloads/765/tools/quickreference/isr.pdf

    HWICs are much faster - 400 Mbps (but if you install a WIC you
    probably fall back to the old limit).

    837 may have an integrated WIC or possibly something a bit better -
    never opened one up to look.

    Finally you should swap the routers between the 2 lines during testing
    - the ISP may have a bottleneck for the IP thruput on a line which
    reduces the available performance.

    >
    >Today I will try with another c837 on the line (1) and I will post the
    >results.
    >
    >
    >
    >
    >"Stephen" ha scritto nel messaggio
    >news:...
    >
    >On Sat, 26 Feb 2011 11:28:46 +0100, "Elia S."
    ><> wrote:
    >
    >>Hello
    >>is a cisco 837 capable of using a 7mbit adsl line? (negotiated 8128 ADSL-1
    >>type line)
    >>

    >raw thruput figures for IP forwarding:
    >http://www.cisco.com/web/partners/downloads/765/tools/quickreference/routerperformance.pdf
    >
    >>I mean.. since that router does just NAT and nothing else, is the cpu
    >>capable of transferring 7mbit down and 512k up?

    >
    >NAT takes some extra steps over simple IP forwarding, so may not reach
    >these numbers - but you have a bit of headroom
    >
    >note the perf is usually measured on Ethernet ports - that gives the
    >minimum overhead, so driving the ADSL line may cause an issue.
    >>
    >>thank you

    >
    >good luck

    --
    Regards

    - replace xyz with ntl
     
    Stephen, Feb 27, 2011
    #2
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