From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-03-ewr.dyndns.com (mxout-070-ewr.mailhop.org [216.146.33.70]) by lists.bufferbloat.net (Postfix) with ESMTP id 7E14D2E03C0 for ; Wed, 16 Mar 2011 15:48:42 -0700 (PDT) Received: from scan-01-ewr.mailhop.org (scanner [10.0.141.223]) by mail-03-ewr.dyndns.com (Postfix) with ESMTP id 64E217898CB for ; Wed, 16 Mar 2011 22:48:41 +0000 (UTC) X-Spam-Score: -8.0 (--------) X-Mail-Handler: MailHop by DynDNS X-Originating-IP: 171.68.10.87 Received: from sj-iport-5.cisco.com (sj-iport-5.cisco.com [171.68.10.87]) by mail-03-ewr.dyndns.com (Postfix) with ESMTP id B37ED7898CA for ; Wed, 16 Mar 2011 22:48:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=cisco.com; i=fred@cisco.com; l=1629; q=dns/txt; s=iport; t=1300315720; x=1301525320; h=subject:mime-version:from:in-reply-to:date:cc:message-id: references:to:content-transfer-encoding; bh=SeL3oagN8wFuIm6N7U/j0uy2VuBfQZQ7Jk30L5VvMII=; b=QCKtbuf8aanh8g0KSexL61WjsbsuLucr+uSjbnDrO83dx8LOT438vH7V yejKcAEJE+dh5RmwUasdIUOgNfDMkz9VHPzuQl7CfXSJFA36YVjyMCqOr MhGJsyZwYhteLLxA6gbU+e7DJXtNJQ2Q7ckjVB5C8ThLzPTEs+mpd3XkW I=; X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AvsEAP/agE2tJV2c/2dsb2JhbAClTXelbZxWhWMEhS+HL4NN X-IronPort-AV: E=Sophos;i="4.63,195,1299456000"; d="scan'208";a="347953454" Received: from rcdn-core-5.cisco.com ([173.37.93.156]) by sj-iport-5.cisco.com with ESMTP; 16 Mar 2011 22:48:39 +0000 Received: from stealth-10-32-244-221.cisco.com (stealth-10-32-244-221.cisco.com [10.32.244.221]) by rcdn-core-5.cisco.com (8.14.3/8.14.3) with ESMTP id p2GMmYxb014841; Wed, 16 Mar 2011 22:48:39 GMT Received: from [127.0.0.1] by stealth-10-32-244-221.cisco.com (PGP Universal service); Wed, 16 Mar 2011 15:48:39 -0700 X-PGP-Universal: processed; by stealth-10-32-244-221.cisco.com on Wed, 16 Mar 2011 15:48:39 -0700 Mime-Version: 1.0 (Apple Message framework v1082) From: Fred Baker In-Reply-To: <580BEA5E3B99744AB1F5BFF5E9A3C67D01708ED2A4@HE111648.emea1.cds.t-internal.com> Date: Wed, 16 Mar 2011 15:48:23 -0700 Message-Id: <0D064802-2668-4FB7-A0BB-8F717DD4CAF8@cisco.com> References: <4D7F4121.40307@freedesktop.org> <580BEA5E3B99744AB1F5BFF5E9A3C67D01708ED2A4@HE111648.emea1.cds.t-internal.com> To: "" X-Mailer: Apple Mail (2.1082) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Cc: bloat@lists.bufferbloat.net Subject: Re: [Bloat] Random idea in reaction to all the discussion of TCP flavours - timestamps? X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 16 Mar 2011 22:48:42 -0000 On Mar 16, 2011, at 2:04 AM, = wrote: > This reminds me of a related concept, using the TTL really as 'Time To = Live' (in today's IP, it's more of a 'Remaining Hop Count). According to = RfC 791, a router that buffers a packet by n seconds must decrease its = TTL by n. I doubt that many routers implement this properly. There is, of course, a fundamental bug in that, noted in RFC 970. RFC 1812, which I edited, contains this text (that I didn't write): In this specification, we have reluctantly decided to follow the strong belief among the router vendors that the time limit function should be optional. They argued that implementation of the time limit function is difficult enough that it is currently not generally done. They further pointed to the lack of documented cases where this shortcut has caused TCP to corrupt data (of course, we would expect the problems created to be rare and difficult to reproduce, so the lack of documented cases provides little reassurance that there haven't been a number of undocumented cases). The corresponding field in IPv6 (RFC 2460) picks up this bit of wisdom: Hop Limit 8-bit unsigned integer. Decremented by 1 by each node that forwards the packet. The packet is discarded if Hop Limit is decremented to zero. I think that you will find that every router implements the hop limit = properly, and implements the TTL as modified by RFC 1812 properly.=