Re: [RFC/PATCH] IMQ port to 2.6

From: Vladimir B. Savkin (master_at_sectorb.msk.ru)
Date: 01/26/04

  • Next message: Heilmann, Oliver: "[PATCH] AGPGART preliminary SiS648 support - fixed and shrunk"
    Date:	Mon, 26 Jan 2004 12:32:30 +0300
    To: jamal <hadi@cyberus.ca>
    
    

    On Sun, Jan 25, 2004 at 10:09:48PM -0500, jamal wrote:
    > On Sun, 2004-01-25 at 19:11, Vladimir B. Savkin wrote:
    > > On Sun, Jan 25, 2004 at 06:45:16PM -0500, jamal wrote:
    > [..]
    > >
    > > With typical internet traffic patterns, policing will drop many packets,
    > > and shaping will not.
    >
    > What is typical internet traffic? I guess you mean TCP (thats what 90%
    > of the traffic is)
    > In that case, the effect of dropping or delaying on throughput is
    > similar. Studies i have seen indicate that throughput is directly
    > proportional to the square root of the drop probability
    > (drop is what you get when you police).
    > It is also influenced by the delay (which is what you introduce when you
    > shape). I have not seen anything in favor of shaping; i could be wrong
    > (so if you know of something or have experimented pass the data).

    Yes, I have experimented. Shaping works much better:
    much less packets dropped, much better donwload rates for clients.

    > For detailed analysis at least fro RENO, this would be a good reference:
    > http://citeseer.nj.nec.com/padhye98modeling.html
    >
    [snip]
    > Maybe i am misunderstanding what you are after.
    > couldnt you use -i ppp+ -j mark --set-mark x in the ingress/prerouting
    > and use the fwmark to shape on the egress?
    > Post your script examples.
    >

    I want to shape traffic that comes from upstream to clients connected
    via PPTP.

    Here is a part of my scripts:

    DEVICE=imq0
    /sbin/tc qidisc add dev $DEVICE root handle 10: htb r2q 1 default 100
    /sbin/tc class add dev $DEVICE parent 10:0 classid 10:1 est 1sec 8sec htb \
            rate 10Mbit burst 400k
    /sbin/tc class add dev $DEVICE parent 10:1 classid 10:2 est 1sec 8sec htb \
            rate 180kbps ceil 180kbps burst 3000
    # default class for users
    /sbin/tc class add dev $DEVICE parent 10:2 classid 10:101 est 1sec 8sec htb \
            rate 20kbps burst 1k ceil 50kbps cburst 1k
    /sbin/tc qdisc add dev $DEVICE parent 10:101 wrr \
            dest ip 128 1 wmode1=1 wmode2=1
    /sbin/tc filter add dev $DEVICE protocol ip parent 10:0 \
            prio 100 handle 1 fw flowid 10:101
    # more classes to follow ...

    The limit 50kbps is artificial, so there's no bottleneck in
    connection from upstream to this router. I cannot allocate all
    the channel bandwidth to clients for some political reasons.
    Then, I mark packets I want to go to this default user class with mark "1",
    like this:

    iptables -t mangle -A FORWARD -i $UPLINK_DEV -d $CLIENTS_NET \
            -j IMQ --todev 0 # traffic from internet to clients
    iptables -t mangle -A FORWARD -i $UPLINK_DEV -d $CLIENTS_NET \
            -j MARK --set-mark 1 # default class
    # here I can change fwmark for packets that deserve
    # some special treatment

    So, I shape traffic destined to clients, and I use "wrr" to
    divide bandwidth fairly. I cannot attach qdisc to an egress device
    because there's no single one, each client has its own ppp interface.

    Well, I could move this shaping upstream, but what if upstream router was
    some dumb cisco with no "wrr" qdisc?

    ~
    :wq
                                            With best regards,
                                               Vladimir Savkin.

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  • Next message: Heilmann, Oliver: "[PATCH] AGPGART preliminary SiS648 support - fixed and shrunk"

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