From owner-freebsd-hackers@FreeBSD.ORG Thu Sep 18 02:08:06 2003 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 1A7D216A4B3 for ; Thu, 18 Sep 2003 02:08:06 -0700 (PDT) Received: from firecrest.mail.pas.earthlink.net (firecrest.mail.pas.earthlink.net [207.217.121.247]) by mx1.FreeBSD.org (Postfix) with ESMTP id 6022743FE5 for ; Thu, 18 Sep 2003 02:08:05 -0700 (PDT) (envelope-from tlambert2@mindspring.com) Received: from user-2ivfk1k.dialup.mindspring.com ([165.247.208.52] helo=mindspring.com) by firecrest.mail.pas.earthlink.net with asmtp (SSLv3:RC4-MD5:128) (Exim 3.33 #1) id 19zulf-0001eA-00; Thu, 18 Sep 2003 02:08:04 -0700 Message-ID: <3F6975BD.14CD05EE@mindspring.com> Date: Thu, 18 Sep 2003 02:07:09 -0700 From: Terry Lambert X-Mailer: Mozilla 4.79 [en] (Win98; U) X-Accept-Language: en MIME-Version: 1.0 To: deepak@ai.net References: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-ELNK-Trace: b1a02af9316fbb217a47c185c03b154d40683398e744b8a4eba4698defad51030e2c519c4f9155ce350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c cc: "freebsd-hackers@FreeBSD. ORG" Subject: Re: TCP information X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 18 Sep 2003 09:08:06 -0000 Deepak Jain wrote: > Is there a utility/hack/patch that would allow a diligent sysadmin to obtain > which specific TCP connections are generating retransmits and receiving > packet drops? netstat will show me drops on an interface, but not on a > specific source/dest pair? > > I am guessing something like a netstat -n, but instead of showing send/rec > queues it shows retransmit or packet drops? Would there be much interest in > this feature if we were to build it ourselves? These types of statistics aren't kept. Generally, they are used only by network researchers, who hack their stacks to get them. They usually do not make it into commercial product distributions for performance reasons, and because every byte added to a tcpcb structure is one byte less that can be used for something else. In practice, adding 134 bytes of statistics to a tcpcb would double its size and halve the number of simultaneous connections you would be able to support with the same amount of RAM in a given machine (as one example), if all of that memory had to come out of the same space, all other things being equal. -- Terry