ADSL numbers.

Discussion in 'NZ Computing' started by Crash, Jan 25, 2006.

  1. Crash

    Crash Guest

    Greetings,

    I am wondering how the speed reported by my ADSL modem (D-LINK DSL-504G) relates
    to the rated speed of my ADSL service.

    The speed from the modem is reported as:

    Downstream: 4704 Kbps Upstream: 320 Kbps

    I am on the Xtra Swift package (no longer sold) of 2 megs download 192K upload.

    If Kbps = 1000 bits per second, 2 megs is in bytes and there are 8 bits per byte
    then I should be getting around (2megs x 8) 16000 Kbps downstream and (192K x 8)
    1536 Kbps upstream. Clearly my assumption is wrong here or I am being
    severely short-changed 8-( The same principles apply if the package speed is
    bits not bytes.

    If Kbps = 1000 bytes per second then the reported speeds are double my package
    entitlement.

    I am aware that actual speed is very volatile and not likely to get anywhere
    near the package speed but would like to know how to accurately compare these
    numbers.

    Crash.
    Crash, Jan 25, 2006
    #1
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  2. Crash

    EMB Guest

    Crash wrote:
    > Greetings,
    >
    > I am wondering how the speed reported by my ADSL modem (D-LINK DSL-504G)
    > relates to the rated speed of my ADSL service.
    >
    > The speed from the modem is reported as:
    >
    > Downstream: 4704 Kbps Upstream: 320 Kbps
    >
    > I am on the Xtra Swift package (no longer sold) of 2 megs download 192K
    > upload.


    Xtra's Jetstream isn't rate limited by line speed (as opposed to UBS
    which is). Xtra do their traffic shaping within their network instead.
    The figures you are seeing are the maximum that you line can support.

    --
    EMB
    EMB, Jan 26, 2006
    #2
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  3. Crash

    Enkidu Guest

    Crash wrote:
    > Greetings,
    >
    > I am wondering how the speed reported by my ADSL modem (D-LINK DSL-504G)
    > relates to the rated speed of my ADSL service.
    >
    > The speed from the modem is reported as:
    >
    > Downstream: 4704 Kbps Upstream: 320 Kbps
    >

    The numbers are kilobits/sec

    Cheers,

    Cliff
    Enkidu, Jan 26, 2006
    #3
  4. Crash

    Steve Guest

    On Thu, 26 Jan 2006 11:13:12 +1300, Crash wrote:

    > Greetings,
    >
    > I am wondering how the speed reported by my ADSL modem (D-LINK DSL-504G) relates
    > to the rated speed of my ADSL service.
    >
    > The speed from the modem is reported as:
    >
    > Downstream: 4704 Kbps Upstream: 320 Kbps
    >
    > I am on the Xtra Swift package (no longer sold) of 2 megs download 192K upload.
    >
    > If Kbps = 1000 bits per second, 2 megs is in bytes and there are 8 bits per byte
    > then I should be getting around (2megs x 8) 16000 Kbps downstream and (192K x 8)
    > 1536 Kbps upstream. Clearly my assumption is wrong here or I am being
    > severely short-changed 8-( The same principles apply if the package speed is
    > bits not bytes.

    No. 2meg = 2 megabits. With 8 bits + stop bits, in reality ou'll get
    200+KBytes/sec max.
    >
    > If Kbps = 1000 bytes per second then the reported speeds are double my
    > package entitlement.

    The speeds are artificially limited at the exchange. What you;re seeing is
    what the line is capable of.
    >
    > I am aware that actual speed is very volatile and not likely to get
    > anywhere near the package speed but would like to know how to accurately
    > compare these numbers.
    >
    > Crash.

    The real downer is the uplink, which Telecom brought down from 256 to
    128kbit ):
    Steve, Jan 26, 2006
    #4
  5. Crash

    Mark C Guest

    Steve <> wrote in
    news:p:

    > On Thu, 26 Jan 2006 11:13:12 +1300, Crash wrote:
    >
    >> I am wondering how the speed reported by my ADSL modem (D-LINK
    >> DSL-504G) relates to the rated speed of my ADSL service.
    >>
    >> The speed from the modem is reported as:
    >>
    >> Downstream: 4704 Kbps Upstream: 320 Kbps
    >>
    >> I am on the Xtra Swift package (no longer sold) of 2 megs
    >> download 192K upload.
    >>
    >> If Kbps = 1000 bits per second, 2 megs is in bytes and there
    >> are 8 bits per byte then I should be getting around (2megs x 8)
    >> 16000 Kbps downstream and (192K x 8)
    >> 1536 Kbps upstream. Clearly my assumption is wrong here or I
    >> am being
    >> severely short-changed 8-( The same principles apply if the
    >> package speed is bits not bytes.

    >
    > No. 2meg = 2 megabits. With 8 bits + stop bits, in reality ou'll
    > get 200+KBytes/sec max.


    No, there are no stop bits; DSL is synchronous.

    You'll get ~250 kbps.

    There are TCP/IP framing bytes, ~40 bytes per packet (usual packet
    size 1,500 bytes, containing 1,460 bytes of payload).
    The TCP/IP framing bytes may or may not be included in the Telecom 2
    mbps rate.

    Mark
    Mark C, Jan 26, 2006
    #5
  6. Crash

    Mark C Guest

    Steve <> wrote in
    news:p:

    > On Thu, 26 Jan 2006 11:13:12 +1300, Crash wrote:
    >
    >> I am wondering how the speed reported by my ADSL modem (D-LINK
    >> DSL-504G) relates to the rated speed of my ADSL service.
    >>
    >> The speed from the modem is reported as:
    >>
    >> Downstream: 4704 Kbps Upstream: 320 Kbps
    >>
    >> I am on the Xtra Swift package (no longer sold) of 2 megs
    >> download 192K upload.
    >>
    >> If Kbps = 1000 bits per second, 2 megs is in bytes and there
    >> are 8 bits per byte then I should be getting around (2megs x 8)
    >> 16000 Kbps downstream and (192K x 8)
    >> 1536 Kbps upstream. Clearly my assumption is wrong here or I
    >> am being
    >> severely short-changed 8-( The same principles apply if the
    >> package speed is bits not bytes.

    >
    > No. 2meg = 2 megabits. With 8 bits + stop bits, in reality ou'll
    > get 200+KBytes/sec max.


    No, there are no stop bits; DSL is synchronous.

    You'll get ~250 kBps.

    There are TCP/IP framing bytes, ~40 bytes per packet (usual packet
    size 1,500 bytes, containing 1,460 bytes of payload).
    The TCP/IP framing bytes may or may not be included in the Telecom 2
    mbps rate.

    Mark
    Mark C, Jan 26, 2006
    #6
  7. Crash

    Mark C Guest

    Mark C <> wrote in
    news:43d89abc$0$1586$:

    > You'll get ~250 kbps.


    Sorry, I meant ~250 kBytes/sec
    Mark C, Jan 26, 2006
    #7
  8. On Thu, 26 Jan 2006 20:37:07 +1300, Steve <> wrote:

    >On Thu, 26 Jan 2006 11:13:12 +1300, Crash wrote:
    >
    >> Greetings,
    >>
    >> I am wondering how the speed reported by my ADSL modem (D-LINK DSL-504G) relates
    >> to the rated speed of my ADSL service.
    >>
    >> The speed from the modem is reported as:
    >>
    >> Downstream: 4704 Kbps Upstream: 320 Kbps
    >>
    >> I am on the Xtra Swift package (no longer sold) of 2 megs download 192K upload.
    >>
    >> If Kbps = 1000 bits per second, 2 megs is in bytes and there are 8 bits per byte
    >> then I should be getting around (2megs x 8) 16000 Kbps downstream and (192K x 8)
    >> 1536 Kbps upstream. Clearly my assumption is wrong here or I am being
    >> severely short-changed 8-( The same principles apply if the package speed is
    >> bits not bytes.

    >No. 2meg = 2 megabits. With 8 bits + stop bits, in reality ou'll get
    >200+KBytes/sec max.


    No stop bits. It is a PPP over ATM over ADSL connection, not an
    asynchronous connection. Even dial-up modem connections are
    synchronous now.

    My real-life 2 Mibit/s UBS (Ihug) connection gives me 256 Kibytes/s of
    TCP/IP bandwidth. To get your actual download bandwidth, you have to
    take off the TCP/IP overheads from that and also the overheads for the
    protocol you are using (eg HTTP, FTP, NNTP). But the ATM and PPP
    overheads are not counted in the 2 Mibit/s - the PPP connection is
    done so that you are delivered a full 2 Mibit/s by PPP.

    >> If Kbps = 1000 bytes per second then the reported speeds are double my
    >> package entitlement.

    >The speeds are artificially limited at the exchange. What you;re seeing is
    >what the line is capable of.


    Yes, Telecom has what they call a "rate file" which lists each
    connection and what speed it should have. The speed is limited by the
    router that the rate file is loaded on. When I was on a 128 Kibit/s
    Jetstream Starter connection via Telecom, I had a couple of faults
    where they had to change the line card I was connected to at the
    exchange. Each time that happened, until the new rate file was
    automatically sent to the routers well after midnight, I got the full
    ADSL bandwidth, which was over 4 Mibit/s in my case, very similar to
    what Crash's modem is reporting for his connection.

    I am not sure if Crash's modem is using K = 1024 or K = 1000 (the
    latter most probably), but in any case those are normally the raw ADSL
    speed available, after which you have to take off the ATM and PPP
    protocol overheads to get the available TCP/IP bandwidth. And "bps"
    in this case clearly means "bits per second" - if it was bytes, the
    figures would be larger than standard ADSL can support, even
    theoretically.

    >> I am aware that actual speed is very volatile and not likely to get
    >> anywhere near the package speed but would like to know how to accurately
    >> compare these numbers.
    >>
    >> Crash.

    >The real downer is the uplink, which Telecom brought down from 256 to
    >128kbit ):
    Stephen Worthington, Jan 26, 2006
    #8
  9. Crash

    ~misfit~ Guest

    Mark C wrote:
    > No, there are no stop bits; DSL is synchronous.
    >
    > You'll get ~250 kBps.


    I can vouch for that. With my Orcon 2M plan sometimes, when downloading from
    HTTP sites, I sometimes get a consistant 256kB/s. (I have DU Meter running,
    graphical representation "always on top").
    --
    ~misfit~
    ~misfit~, Jan 26, 2006
    #9
  10. Crash

    Crash Guest

    Stephen Worthington wrote:
    [snip]
    >
    > I am not sure if Crash's modem is using K = 1024 or K = 1000 (the
    > latter most probably but in any case those are normally the raw ADSL
    > speed available, after which you have to take off the ATM and PPP
    > protocol overheads to get the available TCP/IP bandwidth. And "bps"
    > in this case clearly means "bits per second" - if it was bytes, the
    > figures would be larger than standard ADSL can support, even
    > theoretically.


    Thanks Stephen. I was really after a comparison of '4707 Kbps' compared to my
    '2 meg' plan and '250 Kbps' to my '192K plan'. At least those were the numbers
    I signed up for on the swift plan that Telecom tell me I am still on.

    Judging by the responses the Telecom numbers are in bits and the 4707 Kbps,
    being 4.707 Mbps is twice my plan rate. If the ADSL modem speeds reported drop
    below the Telecom rated speeds (either direction) then the modem may be limiting
    network bandpass. Currently it aint so I am relatively happy. I realise that
    the real bandpass available at any given time (either direction) is another
    matter entirely and likely to be lower than the plan.

    Many thanks for all the responses.

    Crash.
    Crash, Jan 27, 2006
    #10
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