Date: Thu, 18 Sep 2003 02:07:09 -0700 From: Terry Lambert <tlambert2@mindspring.com> To: deepak@ai.net Cc: "freebsd-hackers@FreeBSD. ORG" <freebsd-hackers@FreeBSD.ORG> Subject: Re: TCP information Message-ID: <3F6975BD.14CD05EE@mindspring.com> References: <GPEOJKGHAMKFIOMAGMDIMEHHELAC.deepak@ai.net>
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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
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