From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-x232.google.com (mail-ig0-x232.google.com [IPv6:2607:f8b0:4001:c05::232]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id CFB8F21F2F1 for ; Tue, 3 Mar 2015 10:12:33 -0800 (PST) Received: by igal13 with SMTP id l13so27709548iga.1 for ; Tue, 03 Mar 2015 10:12:32 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=YFQM/cwdTTADD6A0UP3xkfrJdziqpKEKMqdleTquzKQ=; b=eiwnonjDK9cndT4GREbIM8yDHhIZGuKjMu6tpUQiuuBFFlzzwT69eJmYiuFl9/4DYa iHPXDTacL2Td1JpVjvtcQQGFAssJ6Bv3qr2+o/x2yIcxD3YDt40K+KRQnHsvYwLONG7T itgNQmszCRZoo0JpiTVTkISF5hDF1ItBupgw7NSk3CtT6vp/+evgAu3sF5UU9wapBVpu RiKcKJ4pPWIcoDlZaacun8dNz8FHIAAtXjBj5AM6oBuOQ8cBnTMEjrQDVvdt6ARcPP7/ +KTFLm1xJeZ6Qo+3LSqfHog/X+0Wy/Gk/ha+Z2PSiqebUCnXst3wdS4ZfLPu08Mcub55 rb4w== MIME-Version: 1.0 X-Received: by 10.107.130.25 with SMTP id e25mr3865680iod.49.1425406352664; Tue, 03 Mar 2015 10:12:32 -0800 (PST) Received: by 10.107.156.201 with HTTP; Tue, 3 Mar 2015 10:12:32 -0800 (PST) In-Reply-To: References: <5EDCCC18D27F4F039FA971B3C834A466@srichardlxp2> <20150226151457.75fc898b@urahara> Date: Tue, 3 Mar 2015 23:42:32 +0530 Message-ID: From: divya singla To: Jonathan Morton , Richard Scheffenegger Content-Type: multipart/alternative; boundary=001a113fb6d64fdaaa0510664757 Cc: codel@lists.bufferbloat.net Subject: Re: [Codel] About Packet Drop in Codel X-BeenThere: codel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: CoDel AQM discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 03 Mar 2015 18:13:02 -0000 --001a113fb6d64fdaaa0510664757 Content-Type: text/plain; charset=UTF-8 But Sir i heard that UDP does not respond to congestion.Even though its packets are lost, it keeps sending packets at the same rate(unlike tcp) -- please answer this too: Does codel implement concept of marking(ECN) in ns2? On Tue, Mar 3, 2015 at 12:37 AM, Jonathan Morton wrote: > With UDP, you're at the mercy of the application using it. With TCP, > you're merely at the mercy of the operating system. > > AQM acts on UDP packets in the same way as TCP packets - in fact it can't > tell them apart. So any application which detects and responds to UDP > packet loss in the same way as TCP does, will back off just the same. > > In practice, UDP is used for several different types of application: > > - simple request response, such as DNS and NTP, where eliminating TCP's > connection setup overhead is important. In any case, TCP's congestion > control doesn't get a chance to do any good on such s short-lived > connection. Packet loss in this situation is tolerated by retry, with > exponential backoff as an alternative congestion control measure. > > - latency sensitive and often isochronous (inelastic) flows like VoIP. > Packet loss may lead to a loss of quality, but there is little the > application can do to reduce its loss except dropping the call completely. > > - as a way to implement delay sensitive and pacific congestion control > algorithms, as in uTP. > > A flow isolation system, such as that in fq_codel, will often leave UDP > flows alone completely, because they tend not to be the ones using the bulk > of the bandwidth. Conversely, if a single UDP flow was responsible for the > congestion, it would let the other traffic bypass it. This is why fq_codel > is better than just plain codel, if you can get it. > > - Jonathan Morton > --001a113fb6d64fdaaa0510664757 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
But Sir i heard that UDP does not respond to congestion.Ev= en though its packets are lost, it keeps sending packets at the same rate(u= nlike tcp)

-- please answer this too:
=C2=A0Do= es codel implement concept of marking(ECN) =C2=A0in ns2?


On Tue, M= ar 3, 2015 at 12:37 AM, Jonathan Morton <chromatix99@gmail.com>= wrote:

With UDP, y= ou're at the mercy of the application using it. With TCP, you're me= rely at the mercy of the operating system.

AQM acts on UDP packets in the same way as TCP packets - in = fact it can't tell them apart. So any application which detects and res= ponds to UDP packet loss in the same way as TCP does, will back off just th= e same.

In practice, UDP is used for several different types of appl= ication:

- simple request response, such as DNS and NTP, where elimin= ating TCP's connection setup overhead is important. In any case, TCP= 9;s congestion control doesn't get a chance to do any good on such s sh= ort-lived connection. Packet loss in this situation is tolerated by retry, = with exponential backoff as an alternative congestion control measure.

- latency sensitive and often isochronous (inelastic) flows = like VoIP. Packet loss may lead to a loss of quality, but there is little t= he application can do to reduce its loss except dropping the call completel= y.

- as a way to implement delay sensitive and pacific congesti= on control algorithms, as in uTP.

A flow isolation system, such as that in fq_codel, will ofte= n leave UDP flows alone completely, because they tend not to be the ones us= ing the bulk of the bandwidth. Conversely, if a single UDP flow was respons= ible for the congestion, it would let the other traffic bypass it. This is = why fq_codel is better than just plain codel, if you can get it.

- Jonathan Morton


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