Traffic shaping at home on an ADSL connection

Discussion in 'Cisco' started by Voitec, May 13, 2005.

  1. Voitec

    Voitec Guest

    Hi,

    I'd like to purchase a router with which to do traffic shaping on my ADSL
    connection at home. So far I'm narrowing it down to a Cisco 1751 +
    WIC-1ADSL.

    Questions:
    1) Is there a better/cheaper option than the one above? Should I be looking
    at a 1721, 1701 or something else?
    2) Can one specify the traffic shaping policies on the ADSL interface, the
    Ethernet interface, or either?
    3) What's the preferred way to treat HTTP traffic (ie. web browsing) with
    the highest priority? I am just reading about NBAR.


    Current setup:
    A number of PCs connected via a non-Cisco switch to a non-Cisco router.

    Clearly, whenever I am streaming video or downloading large files, web
    browsing and email traffic suffers. Subsequently, I would like to upgrade my
    equipment to allow traffic shaping whereby web browsing, email and chat
    would get highest priority. This is to avoid the various time out messages
    one gets at the moment whilst streaming data or downloading large files.

    I'd appreciate if someone could point me in the right direction. Cisco or
    other links are welcome :)

    Thanks,
    Voitec
     
    Voitec, May 13, 2005
    #1
    1. Advertising

  2. Voitec

    Voitec Guest

    With regard to Question 1, just adding to my router alternatives: Cisco 837.
    Cheapest option but will it do the job?


    "Voitec" <> wrote in message
    news:8o0he.1621$...
    > Hi,
    >
    > I'd like to purchase a router with which to do traffic shaping on my ADSL
    > connection at home. So far I'm narrowing it down to a Cisco 1751 +
    > WIC-1ADSL.
    >
    > Questions:
    > 1) Is there a better/cheaper option than the one above? Should I be

    looking
    > at a 1721, 1701 or something else?
    > 2) Can one specify the traffic shaping policies on the ADSL interface, the
    > Ethernet interface, or either?
    > 3) What's the preferred way to treat HTTP traffic (ie. web browsing) with
    > the highest priority? I am just reading about NBAR.
    >
    >
    > Current setup:
    > A number of PCs connected via a non-Cisco switch to a non-Cisco router.
    >
    > Clearly, whenever I am streaming video or downloading large files, web
    > browsing and email traffic suffers. Subsequently, I would like to upgrade

    my
    > equipment to allow traffic shaping whereby web browsing, email and chat
    > would get highest priority. This is to avoid the various time out messages
    > one gets at the moment whilst streaming data or downloading large files.
    >
    > I'd appreciate if someone could point me in the right direction. Cisco or
    > other links are welcome :)
    >
    > Thanks,
    > Voitec
    >
    >
     
    Voitec, May 13, 2005
    #2
    1. Advertising

  3. You can determine whether traffic shaping is supported by researching
    the IOS image & platform on the Cisco website. A 1720 is fine with a
    WIC-1ADSL with 16MB flash/48MB DRAM, but the cost of those items
    purchased used ($500+) would far exceed the cost of a used 837 on eBay
    for around ($350). I think that you can also do traffic shaping on and
    827/827-4v with a late 12.3/12.4 IOS.

    It also depends what other functionality you want from your IOS
    feature set & how much $ you want to spend.
    ==============================================
    On Fri, 13 May 2005 11:59:56 GMT, "Voitec" <>
    wrote:

    >With regard to Question 1, just adding to my router alternatives: Cisco 837.
    >Cheapest option but will it do the job?
    >
    >
    >"Voitec" <> wrote in message
    >news:8o0he.1621$...
    >> Hi,
    >>
    >> I'd like to purchase a router with which to do traffic shaping on my ADSL
    >> connection at home. So far I'm narrowing it down to a Cisco 1751 +
    >> WIC-1ADSL.
    >>
    >> Questions:
    >> 1) Is there a better/cheaper option than the one above? Should I be

    >looking
    >> at a 1721, 1701 or something else?
    >> 2) Can one specify the traffic shaping policies on the ADSL interface, the
    >> Ethernet interface, or either?
    >> 3) What's the preferred way to treat HTTP traffic (ie. web browsing) with
    >> the highest priority? I am just reading about NBAR.
    >>
    >>
    >> Current setup:
    >> A number of PCs connected via a non-Cisco switch to a non-Cisco router.
    >>
    >> Clearly, whenever I am streaming video or downloading large files, web
    >> browsing and email traffic suffers. Subsequently, I would like to upgrade

    >my
    >> equipment to allow traffic shaping whereby web browsing, email and chat
    >> would get highest priority. This is to avoid the various time out messages
    >> one gets at the moment whilst streaming data or downloading large files.
    >>
    >> I'd appreciate if someone could point me in the right direction. Cisco or
    >> other links are welcome :)
    >>
    >> Thanks,
    >> Voitec
    >>
    >>

    >
     
    X--Eliminator, May 13, 2005
    #3
  4. Voitec

    stephen Guest

    "Voitec" <> wrote in message
    news:0F0he.1639$...
    > With regard to Question 1, just adding to my router alternatives: Cisco

    837.
    > Cheapest option but will it do the job?
    >
    >
    > "Voitec" <> wrote in message
    > news:8o0he.1621$...
    > > Hi,
    > >
    > > I'd like to purchase a router with which to do traffic shaping on my

    ADSL
    > > connection at home. So far I'm narrowing it down to a Cisco 1751 +
    > > WIC-1ADSL.
    > >
    > > Questions:
    > > 1) Is there a better/cheaper option than the one above? Should I be

    > looking


    have a look at the new 1801 - $1000 list bundle including ADSL (and ISDN
    backup if you want that) - no embedded Voip interfaces - which is the only
    reason you would have gone for 1751 over a 1721.

    www.cisco.com/go/isr

    > > at a 1721, 1701 or something else?
    > > 2) Can one specify the traffic shaping policies on the ADSL interface,

    the
    > > Ethernet interface, or either?


    Yes
    > > 3) What's the preferred way to treat HTTP traffic (ie. web browsing)

    with
    > > the highest priority? I am just reading about NBAR.
    > >


    usually you dont - HTTP is well behaved compared to many protocols, so
    voice, streaming and various others tend to be given higher priority.
    > >
    > > Current setup:
    > > A number of PCs connected via a non-Cisco switch to a non-Cisco router.
    > >
    > > Clearly, whenever I am streaming video or downloading large files, web
    > > browsing and email traffic suffers. Subsequently, I would like to

    upgrade
    > my
    > > equipment to allow traffic shaping whereby web browsing, email and chat
    > > would get highest priority. This is to avoid the various time out

    messages
    > > one gets at the moment whilst streaming data or downloading large files.


    The big problem here is that shaping / priority only works if your router
    can control which packets get sent into the bottleneck on a path

    with an Internet feed (which is what this sounds like), you cannot apply
    priority to the stuff you get sent by your ISP - they would have to do that.
    > >
    > > I'd appreciate if someone could point me in the right direction. Cisco

    or
    > > other links are welcome :)
    > >
    > > Thanks,
    > > Voitec

    --
    Regards

    Stephen Hope - return address needs fewer xxs
     
    stephen, May 14, 2005
    #4
  5. Voitec

    Voitec Guest

    Thank you both.

    It looks like I may settle for the 837 as I don't really need any additional
    bells and whistles offerred by the other models and cost is the main factor
    here since this is only a router for home use. That makes the 1800s bit too
    pricey for my wallet :(

    I understand that in a corporate environment one would want to prioritise
    delay sensitive traffic such as voice but in my home environment where the
    majority of traffic is related to large data transfers and email and http, I
    need to make http #1 to counteract the link saturation that occurs at times
    of large file movements. This is the main reason why I need a router that is
    QoS-capable.

    With regard to an internet connection, why would I not be able to prioritise
    the traffic entering my LAN? Does that mean that I would have to have 2
    routers connected in series to one another before splitting the feed to my
    local PCs? Seems a bit of an overkill...


    "stephen" <> wrote in message
    news:scphe.4873$...
    > "Voitec" <> wrote in message
    > news:0F0he.1639$...
    >> With regard to Question 1, just adding to my router alternatives: Cisco

    > 837.
    >> Cheapest option but will it do the job?
    >>
    >>
    >> "Voitec" <> wrote in message
    >> news:8o0he.1621$...
    >> > Hi,
    >> >
    >> > I'd like to purchase a router with which to do traffic shaping on my

    > ADSL
    >> > connection at home. So far I'm narrowing it down to a Cisco 1751 +
    >> > WIC-1ADSL.
    >> >
    >> > Questions:
    >> > 1) Is there a better/cheaper option than the one above? Should I be

    >> looking

    >
    > have a look at the new 1801 - $1000 list bundle including ADSL (and ISDN
    > backup if you want that) - no embedded Voip interfaces - which is the only
    > reason you would have gone for 1751 over a 1721.
    >
    > www.cisco.com/go/isr
    >
    >> > at a 1721, 1701 or something else?
    >> > 2) Can one specify the traffic shaping policies on the ADSL interface,

    > the
    >> > Ethernet interface, or either?

    >
    > Yes
    >> > 3) What's the preferred way to treat HTTP traffic (ie. web browsing)

    > with
    >> > the highest priority? I am just reading about NBAR.
    >> >

    >
    > usually you dont - HTTP is well behaved compared to many protocols, so
    > voice, streaming and various others tend to be given higher priority.
    >> >
    >> > Current setup:
    >> > A number of PCs connected via a non-Cisco switch to a non-Cisco router.
    >> >
    >> > Clearly, whenever I am streaming video or downloading large files, web
    >> > browsing and email traffic suffers. Subsequently, I would like to

    > upgrade
    >> my
    >> > equipment to allow traffic shaping whereby web browsing, email and chat
    >> > would get highest priority. This is to avoid the various time out

    > messages
    >> > one gets at the moment whilst streaming data or downloading large
    >> > files.

    >
    > The big problem here is that shaping / priority only works if your router
    > can control which packets get sent into the bottleneck on a path
    >
    > with an Internet feed (which is what this sounds like), you cannot apply
    > priority to the stuff you get sent by your ISP - they would have to do
    > that.
    >> >
    >> > I'd appreciate if someone could point me in the right direction. Cisco

    > or
    >> > other links are welcome :)
    >> >
    >> > Thanks,
    >> > Voitec

    > --
    > Regards
    >
    > Stephen Hope - return address needs fewer xxs
    >
    >
     
    Voitec, May 17, 2005
    #5
  6. Voitec

    Jo Reed Guest

    it's not what's entering your lan that's the problem, it's what the ISP
    pushes down your pipe. You have no control over what they push.

    > With regard to an internet connection, why would I not be able to
    > prioritise the traffic entering my LAN? Does that mean that I would have
    > to have 2 routers connected in series to one another before splitting the
    > feed to my local PCs? Seems a bit of an overkill...
     
    Jo Reed, May 17, 2005
    #6
  7. Voitec

    Voitec Guest

    I don't follow. How can an ISP be pushing something down my pipe that I did
    not request? If I'm downloading files and requesting web pages what else is
    there in the equation?

    The bottom line is: I want to give HTTP traffic the top priority
    irrespective if what's entering or exiting my LAN.



    "Jo Reed" <> wrote in message
    news:wCjie.9501$...
    > it's not what's entering your lan that's the problem, it's what the ISP
    > pushes down your pipe. You have no control over what they push.
    >
    > > With regard to an internet connection, why would I not be able to
    > > prioritise the traffic entering my LAN? Does that mean that I would have
    > > to have 2 routers connected in series to one another before splitting

    the
    > > feed to my local PCs? Seems a bit of an overkill...

    >
    >
     
    Voitec, May 17, 2005
    #7
  8. Voitec

    Voitec Guest

    Ooops...typo...the latter should have read:
    "...irrespective if it's entering or exiting my LAN."



    "Voitec" <> wrote in message
    news:eykie.6201$...
    > I don't follow. How can an ISP be pushing something down my pipe that I

    did
    > not request? If I'm downloading files and requesting web pages what else

    is
    > there in the equation?
    >
    > The bottom line is: I want to give HTTP traffic the top priority
    > irrespective if what's entering or exiting my LAN.
    >
    >
    >
    > "Jo Reed" <> wrote in message
    > news:wCjie.9501$...
    > > it's not what's entering your lan that's the problem, it's what the ISP
    > > pushes down your pipe. You have no control over what they push.
    > >
    > > > With regard to an internet connection, why would I not be able to
    > > > prioritise the traffic entering my LAN? Does that mean that I would

    have
    > > > to have 2 routers connected in series to one another before splitting

    > the
    > > > feed to my local PCs? Seems a bit of an overkill...

    > >
    > >

    >
    >
     
    Voitec, May 17, 2005
    #8
  9. Voitec

    Guest

    The "bottom line" is you can't control what
    enters your link. Send me your IP address
    and I can send you unsolicited traffic. I can fake the
    source address so that you don't even know the
    origin of the traffic.

    I bring up new internet connections from time to time
    and unsolicited traffic to the address range usually appears
    right away. I assume that the source is malicious code
    loaded into millions of computers that are scanning the
    whole address space looking for new machines to infect.

    Even in the case where the traffic is requested by you
    you cannot control to achieve effective traffic
    shaping. A simple example is you request a file
    download. You have no direct control of
    how TCP manages the download.

    That is interesting:- In principle, in the case of TCP,
    it should be possible to regulate the receive window to
    manage the network load. I have never heard of this being
    done (but then I don't listen very hard:).

    With UDP though this control is not possible even in principle.
     
    , May 17, 2005
    #9
  10. Voitec

    Voitec Guest

    Hmmm...this thread has taken a detour.

    I agree that unsolicited traffic hits my router on a daily basis. However,
    at any given time such traffic does not take up a noticeable amount of my
    bandwidth. Hence, as far as I'm concerned, and for the purposes of my
    original question, the traffic going across my internet connection is ONLY
    traffic that I have requested.

    So once again let me re-iterate what I am trying to achieve here:
    1) If I do not perform any data downloads/transfers from PC #2 to the
    internet and back, then PC #1 can browse web pages, send emails and do
    whatever it likes. This is irrespective of whether there is any unsolicited
    traffic going across my link or not. As such, for the purposes of the
    exercise, bringing up the notion of me being unable to control what my ISP
    sends me is irrelevant. Why? Because any unsolicited traffic that I may get
    does not in any way have an impact on my ability to use PC #1 for the tasks
    outlined above.

    2) Once PC #2 starts performing heavy data transfers, the internet link gets
    saturated and PC #1 starts having problems. Web pages take a very long time
    to load or they just simply time out. Emails are unable to be sent or
    received as the connection to an external mail server times out. If I stop
    the data transfers on PC #2, PC #1 can once again perform its tasks.

    So, in summary, there's only one reason why my link gets saturated and only
    one reason why PC #1 cannot perform its normal web related tasks: heavy data
    transfers on PC #2.

    As such, I would like to go back to my original question, that is, what is
    the best way to control MY traffic going across the internet connection so
    that the web related tasks of PC #1 are unafffected?

    Apologies if only now I am making myself clear on what I am trying to
    achieve and thanks to everyone that has responded so far.

    Thanks,
    Voitec




    <> wrote in message
    news:...
    > The "bottom line" is you can't control what
    > enters your link. Send me your IP address
    > and I can send you unsolicited traffic. I can fake the
    > source address so that you don't even know the
    > origin of the traffic.
    >
    > I bring up new internet connections from time to time
    > and unsolicited traffic to the address range usually appears
    > right away. I assume that the source is malicious code
    > loaded into millions of computers that are scanning the
    > whole address space looking for new machines to infect.
    >
    > Even in the case where the traffic is requested by you
    > you cannot control to achieve effective traffic
    > shaping. A simple example is you request a file
    > download. You have no direct control of
    > how TCP manages the download.
    >
    > That is interesting:- In principle, in the case of TCP,
    > it should be possible to regulate the receive window to
    > manage the network load. I have never heard of this being
    > done (but then I don't listen very hard:).
    >
    > With UDP though this control is not possible even in principle.
    >
     
    Voitec, May 18, 2005
    #10
  11. Voitec

    stephen Guest

    <> wrote in message
    news:...
    > The "bottom line" is you can't control what
    > enters your link. Send me your IP address
    > and I can send you unsolicited traffic. I can fake the
    > source address so that you don't even know the
    > origin of the traffic.
    >
    > I bring up new internet connections from time to time
    > and unsolicited traffic to the address range usually appears
    > right away. I assume that the source is malicious code
    > loaded into millions of computers that are scanning the
    > whole address space looking for new machines to infect.
    >
    > Even in the case where the traffic is requested by you
    > you cannot control to achieve effective traffic
    > shaping. A simple example is you request a file
    > download. You have no direct control of
    > how TCP manages the download.


    yes - and that assumes all the traffic is TCP. Streamed audio or video often
    doesnt react to network conditions at all.
    >
    > That is interesting:- In principle, in the case of TCP,
    > it should be possible to regulate the receive window to
    > manage the network load. I have never heard of this being
    > done (but then I don't listen very hard:).


    This is practical, and devices like the Packeteer boxes use TCP parameter
    manipulation to try to regulate the stuff coming down a link. Since the TCP
    parameters are "end to end"

    in principle you can do this anywhere on the path between the end points,
    unlike conventional traffic shaping in a router, which acts on streams of
    packets leaving its interfaces and only directly affects downstream traffic.

    The problem is TCP can have a control loop with a long reaction time -
    imagine a UK PC pulling HTTP data from the US west coast, where the round
    trip time is a good fraction of a second. So, any actions your device took
    on TCP going out of your ISP link wont have any affect until at least the
    packets and any reaction to it traverse all the hops along the connection.

    Since HTTP TCP connections in general dont last all that long (often just a
    few round trip exchanges of packets), TCP manipulation is not as effective
    as shaping the flow directly in the intermediate routers.
    >
    > With UDP though this control is not possible even in principle.


    Ok - but the application using UDP may be - things like Real streaming have
    their own feedback mechanisms within the app.
    --
    Regards

    Stephen Hope - return address needs fewer xxs
     
    stephen, May 19, 2005
    #11
  12. Voitec

    Peter Guest

    Hi Voitec,

    > 2) Once PC #2 starts performing heavy data transfers, the internet link gets
    > saturated and PC #1 starts having problems.


    Completely unrelated to traffic shaping, I see a similar situation
    here on my ADSL link, IE when 1 machine is performing a task, another
    machine has a hard time getting a bite of the bandwidth. In fact if I
    perform 2 bandwidth demanding tasks on one machine, this same issue
    pops up between those 2 tasks. This never used to happen, it all
    started happening at exactly the same time as my ISP changed their
    DSLAM manufacturer...

    According to the service provider, the change was made to make more
    efficient use of the "shared" bandwidth upstream from the DSLAM. This
    "improvement" was obtained by a huge buffer in the DSLAM and code to
    slow down the rate of transfer INTO the DSLAM from the source point,
    to REDUCE DROPPED PACKETS, by providing time for the DSLAM to alter
    the window size and therefore the data rate used by the source point.
    This was the "official" reason for their action, but...

    In reality what this does is reduce the TCP retransmits, allowing the
    upstream links to operate at optimum capacity/efficiency. The negative
    effect of this "Bandwidth management" is to cause multiple streams to
    one destination point to be queued in an unnatural manner, destroying
    low latency services such as VoIP, and even audio streaming, from
    operating effectively. Managing the bandwidth from the end users
    perspective is almost impossible in this situation. This means the ISP
    can then charge extra money to provide legacy Telephone services in
    "Competition" to their ADSL service.

    The unanimous agreement from the local ADSL user base here is that the
    sole purpose of this change was to make more money from the end user.

    As we operate here (NZ) in an almost single supplier environment,
    there is not a lot that can be done about it. This may have absolutely
    nothing to do with your situation, but I thought it worth mentioning.

    Cheers..............pk.

    ---
    Peter from Auckland.
     
    Peter, May 20, 2005
    #12
  13. Voitec

    Guest

    Thanks for the Packeteer and Real networks comments.
    I had heard of packeteer and heard some outlandish
    seeming statements about it's capabilities
    but I hadn't previously realised the previously
    discussed TCP window management mechanism as a
    possibility.
     
    , May 20, 2005
    #13
  14. Voitec

    Voitec Guest

    Thanks Peter. Well, that has put a nail in the coffin so to speak.

    I'm in OZ but am not sure of the DSLAM boxes in use. They are probably
    either Siemens or Alcatel.

    With regard to your mention of DSLAM buffering, I would have thought that if
    it exists on my exchange then all traffic would be buffered. That includes
    FTP and HTTP traffic from my PCs. So if the DSLAM does not discriminate
    against HTTP traffic as it treats all traffic in the same way, then going
    back to my original question, why can't I then prioritise this traffic on
    its way out/back?

    Example:
    Traffic leaving PC#2, FTP, is marked with IP Precedence=0 at my gateway
    router, HTTP traffic from PC#1 is marked with IP Precedence=5 at the same
    router. Hence HTTP traffic is the first one to leave my side of the link to
    the ISP. FTP traffic follows. Then the DSLAM buffers the traffic coming from
    my end slowing it down. However, the IP Precedence of this traffic is not
    altered and the traffic then moves out to its destination. On the way back
    ot the DSLAM, the above traffic may or may not be buffered. Irrespective of
    that, when the HTTP and FTP traffic hits my ADSL interface on the way back,
    it is again marked with IP Precedence=0 for FTP and IP Precedence=5 for
    HTTP. As such, PC#1 is the first one to receive its packets.

    What I still don't understand is why, with my very limited Cisco QoS
    knowledge, I'm unable to set up the outgoing ADSL interface of the router to
    prioritise, let's say, the few struggling HTTP packets attempting to leave
    my LAN, so that they can overtake the thousands of bytes of ftp traffic, get
    out to the internet quicker and on their way back overtake the ftp packets
    coming in.

    Sorry if I'm going in circles but I just can't get my head around this...



    "Peter" <> wrote in message
    news:wbmU17UUqwk4-pn2-gsMP5KVEMZCS@otis...
    > Hi Voitec,
    >
    > > 2) Once PC #2 starts performing heavy data transfers, the internet link

    gets
    > > saturated and PC #1 starts having problems.

    >
    > Completely unrelated to traffic shaping, I see a similar situation
    > here on my ADSL link, IE when 1 machine is performing a task, another
    > machine has a hard time getting a bite of the bandwidth. In fact if I
    > perform 2 bandwidth demanding tasks on one machine, this same issue
    > pops up between those 2 tasks. This never used to happen, it all
    > started happening at exactly the same time as my ISP changed their
    > DSLAM manufacturer...
    >
    > According to the service provider, the change was made to make more
    > efficient use of the "shared" bandwidth upstream from the DSLAM. This
    > "improvement" was obtained by a huge buffer in the DSLAM and code to
    > slow down the rate of transfer INTO the DSLAM from the source point,
    > to REDUCE DROPPED PACKETS, by providing time for the DSLAM to alter
    > the window size and therefore the data rate used by the source point.
    > This was the "official" reason for their action, but...
    >
    > In reality what this does is reduce the TCP retransmits, allowing the
    > upstream links to operate at optimum capacity/efficiency. The negative
    > effect of this "Bandwidth management" is to cause multiple streams to
    > one destination point to be queued in an unnatural manner, destroying
    > low latency services such as VoIP, and even audio streaming, from
    > operating effectively. Managing the bandwidth from the end users
    > perspective is almost impossible in this situation. This means the ISP
    > can then charge extra money to provide legacy Telephone services in
    > "Competition" to their ADSL service.
    >
    > The unanimous agreement from the local ADSL user base here is that the
    > sole purpose of this change was to make more money from the end user.
    >
    > As we operate here (NZ) in an almost single supplier environment,
    > there is not a lot that can be done about it. This may have absolutely
    > nothing to do with your situation, but I thought it worth mentioning.
    >
    > Cheers..............pk.
    >
    > ---
    > Peter from Auckland.
    >
     
    Voitec, May 21, 2005
    #14
  15. Voitec

    stephen Guest

    "Voitec" <> wrote in message
    news:M5Hje.10514$...
    > Thanks Peter. Well, that has put a nail in the coffin so to speak.
    >
    > I'm in OZ but am not sure of the DSLAM boxes in use. They are probably
    > either Siemens or Alcatel.
    >
    > With regard to your mention of DSLAM buffering, I would have thought that

    if
    > it exists on my exchange then all traffic would be buffered. That includes
    > FTP and HTTP traffic from my PCs. So if the DSLAM does not discriminate
    > against HTTP traffic as it treats all traffic in the same way, then going
    > back to my original question, why can't I then prioritise this traffic on
    > its way out/back?
    >
    > Example:
    > Traffic leaving PC#2, FTP, is marked with IP Precedence=0 at my gateway
    > router, HTTP traffic from PC#1 is marked with IP Precedence=5 at the same
    > router. Hence HTTP traffic is the first one to leave my side of the link

    to
    > the ISP. FTP traffic follows.


    maybe - the issue is that QoS is basically looking inthe transmit buffer to
    choose which packet goes next - but that choice only makes any sense when
    you have multiple packets to choose from.

    So, if a transmit oppotunity is there, and there is only 1 packet - QoS is
    not going to make any difference

    finally - most IP devices ignore IP precedence etc unless explicitly
    configured to do so

    Then the DSLAM buffers the traffic coming from
    > my end slowing it down.


    No - the likely slowest link from you to an Internet destination is the ADSL
    uplink (256 Kbps here in the UK). Once it gets to the DSLAM it hits an
    aggrgate link, with a capacity in 10s of Mbps.

    However, the IP Precedence of this traffic is not
    > altered and the traffic then moves out to its destination. On the way back
    > ot the DSLAM, the above traffic may or may not be buffered. Irrespective

    of
    > that, when the HTTP and FTP traffic hits my ADSL interface on the way

    back,
    > it is again marked with IP Precedence=0 for FTP and IP Precedence=5 for
    > HTTP. As such, PC#1 is the first one to receive its packets.


    Maybe - some devices dont echo the precedence from incoming packets on
    outgoing packets on the same stream. And even if they did, QoS processing at
    intermediate networks may alter the marking.

    Finally - the DSLAM is free to ignore IP precedence - and the telco is
    likely to force that config. Otherwise there is a risk that every clever
    user would be setting all of their traffic to high precedence, which might
    starve other users of bandwidth.
    >
    > What I still don't understand is why, with my very limited Cisco QoS
    > knowledge, I'm unable to set up the outgoing ADSL interface of the router

    to
    > prioritise, let's say, the few struggling HTTP packets attempting to leave
    > my LAN, so that they can overtake the thousands of bytes of ftp traffic,

    get
    > out to the internet quicker and on their way back overtake the ftp packets
    > coming in.


    QoS is an end to end problem - not a lot of point setting it unless you are
    altering what happens at the major bottlenecks on the paths involved.
    >
    > Sorry if I'm going in circles but I just can't get my head around this...
    >
    >
    >
    > "Peter" <> wrote in message
    > news:wbmU17UUqwk4-pn2-gsMP5KVEMZCS@otis...
    > > Hi Voitec,
    > >
    > > > 2) Once PC #2 starts performing heavy data transfers, the internet

    link
    > gets
    > > > saturated and PC #1 starts having problems.

    > >
    > > Completely unrelated to traffic shaping, I see a similar situation
    > > here on my ADSL link, IE when 1 machine is performing a task, another
    > > machine has a hard time getting a bite of the bandwidth. In fact if I
    > > perform 2 bandwidth demanding tasks on one machine, this same issue
    > > pops up between those 2 tasks. This never used to happen, it all
    > > started happening at exactly the same time as my ISP changed their
    > > DSLAM manufacturer...
    > >
    > > According to the service provider, the change was made to make more
    > > efficient use of the "shared" bandwidth upstream from the DSLAM. This
    > > "improvement" was obtained by a huge buffer in the DSLAM and code to
    > > slow down the rate of transfer INTO the DSLAM from the source point,
    > > to REDUCE DROPPED PACKETS, by providing time for the DSLAM to alter
    > > the window size and therefore the data rate used by the source point.
    > > This was the "official" reason for their action, but...
    > >
    > > In reality what this does is reduce the TCP retransmits, allowing the
    > > upstream links to operate at optimum capacity/efficiency. The negative
    > > effect of this "Bandwidth management" is to cause multiple streams to
    > > one destination point to be queued in an unnatural manner, destroying
    > > low latency services such as VoIP, and even audio streaming, from
    > > operating effectively. Managing the bandwidth from the end users
    > > perspective is almost impossible in this situation. This means the ISP
    > > can then charge extra money to provide legacy Telephone services in
    > > "Competition" to their ADSL service.
    > >
    > > The unanimous agreement from the local ADSL user base here is that the
    > > sole purpose of this change was to make more money from the end user.
    > >
    > > As we operate here (NZ) in an almost single supplier environment,
    > > there is not a lot that can be done about it. This may have absolutely
    > > nothing to do with your situation, but I thought it worth mentioning.
    > >
    > > Cheers..............pk.
    > >
    > > ---
    > > Peter from Auckland.

    --
    Regards

    Stephen Hope - return address needs fewer xxs
     
    stephen, May 21, 2005
    #15
  16. Voitec

    Peter Guest

    Hi Voitec,

    > Thanks Peter. Well, that has put a nail in the coffin so to speak.
    >
    > I'm in OZ but am not sure of the DSLAM boxes in use. They are probably
    > either Siemens or Alcatel.


    We used to have Alcatel here but I think the aforementioned DSLAM's
    are Redback, but I can't be 100% certain.

    > With regard to your mention of DSLAM buffering, I would have thought that if
    > it exists on my exchange then all traffic would be buffered. That includes
    > FTP and HTTP traffic from my PCs. So if the DSLAM does not discriminate
    > against HTTP traffic as it treats all traffic in the same way, then going
    > back to my original question, why can't I then prioritise this traffic on
    > its way out/back?


    Well the process I described is traffic type insensitive, it affects
    ALL traffic regardless.

    As far as QoS is concerned, if you can't apply QoS rules to the entire
    path, you are pretty much wasting your time as there is a 99%
    likelihood your QoS is discarded along the way. Unless you have a
    specific segment issue that QoS can help with, but then you need to be
    able to manage the entire segment.

    > What I still don't understand is why, with my very limited Cisco QoS
    > knowledge, I'm unable to set up the outgoing ADSL interface of the router to
    > prioritise, let's say, the few struggling HTTP packets attempting to leave
    > my LAN, so that they can overtake the thousands of bytes of ftp traffic, get
    > out to the internet quicker and on their way back overtake the ftp packets
    > coming in.


    You can do this for what is leaving the end you manage, but that would
    be all. The real question is, what is going to happen when your data
    hits the next layer 3 part of the chain...

    Cheers.............pk.

    ---
    Peter from Auckland.
     
    Peter, May 22, 2005
    #16
  17. Voitec

    Voitec Guest

    Gentlemen,

    Thank you very much for the detailed explanations and you patience with me
    on this.


    Cheers,
    Voitec


    "Peter" <> wrote in message
    news:wbmU17UUqwk4-pn2-meJX7ftdy7Pl@otis...
    > Hi Voitec,
    >
    > > Thanks Peter. Well, that has put a nail in the coffin so to speak.
    > >
    > > I'm in OZ but am not sure of the DSLAM boxes in use. They are probably
    > > either Siemens or Alcatel.

    >
    > We used to have Alcatel here but I think the aforementioned DSLAM's
    > are Redback, but I can't be 100% certain.
    >
    > > With regard to your mention of DSLAM buffering, I would have thought

    that if
    > > it exists on my exchange then all traffic would be buffered. That

    includes
    > > FTP and HTTP traffic from my PCs. So if the DSLAM does not discriminate
    > > against HTTP traffic as it treats all traffic in the same way, then

    going
    > > back to my original question, why can't I then prioritise this traffic

    on
    > > its way out/back?

    >
    > Well the process I described is traffic type insensitive, it affects
    > ALL traffic regardless.
    >
    > As far as QoS is concerned, if you can't apply QoS rules to the entire
    > path, you are pretty much wasting your time as there is a 99%
    > likelihood your QoS is discarded along the way. Unless you have a
    > specific segment issue that QoS can help with, but then you need to be
    > able to manage the entire segment.
    >
    > > What I still don't understand is why, with my very limited Cisco QoS
    > > knowledge, I'm unable to set up the outgoing ADSL interface of the

    router to
    > > prioritise, let's say, the few struggling HTTP packets attempting to

    leave
    > > my LAN, so that they can overtake the thousands of bytes of ftp traffic,

    get
    > > out to the internet quicker and on their way back overtake the ftp

    packets
    > > coming in.

    >
    > You can do this for what is leaving the end you manage, but that would
    > be all. The real question is, what is going to happen when your data
    > hits the next layer 3 part of the chain...
    >
    > Cheers.............pk.
    >
    > ---
    > Peter from Auckland.
    >
     
    Voitec, May 24, 2005
    #17
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