[H-GEN] TCP question

[Grant, Luke]

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thanks for the pointers guys,

found a little nt command called "arp" which allows you to delete cached
entries so i have simply set it to run every 2 mins.

it is a bit rudimentry but it does the trick.

Luke

--------------------------------------------
Luke Grant
Systems Administrator
Seven Queensland.
Maroochydore
140-142 Horton Pde.
wk#  +61754301737
mob# +61407317951
-------------------------------------------

> -----Original Message-----
> From: Jason McDonald [mailto:jasonm at foxboro.com.au]
> Sent: Sunday, August 20, 2000 10:53 PM
> To: general at lists.humbug.org.au
> Subject: Re: [H-GEN] TCP question
> 
> 
> [ Humbug *General* list - semi-serious discussions about Humbug and ]
> [ Unix-related topics.  Please observe the list's charter.          ]
> 
> 
> > now i run into a problem which makes no sence to me. My 
> test linux-PC
> > doesn't even blink an eyelid...it just keeps on seeing the 
> share like
> > nothing has happened.  BUT. My NT4-PC disconnects and will not
> > ping/map/anything the IP/share for several minutes. 
> Eventualy it switches
> > over but the time  it takes is toooo long for my needs.
> > 
> > so my question (now that you have the background) is, what 
> is causing the
> > TCP in NT to be so slow in responding to a change in 
> possition on the
> > network for an IP?   anyone?  and how can i fix this?
> 
> I suspect that the NT box is not updating it's ARP cache (the list of
> mappings from IP addresses to Ethernet hardware addresses) very often.
> From memory the standard expiry time for an ARP entry is about 20
> minutes.
> 
> It would be interesting to run tcpdump and see how long it 
> takes for the
> NT box to send out an ARP request (to get the new ethernet hardware
> address that matches the target IP address) after the changeover to
> confirm this theory.
> 
> Unfortunately, I'm not sure how to change the default ARP 
> expiry time in
> Windoze.  But something to try would be to have the machine that takes
> over the share send out a broadcast ICMP request packet (i.e. 
> a ping to
> the network's broadcast address (possibly 10.0.0.255 or the 
> like)) when it
> takes control of the IP address.  
> 
> Some TCP stacks will use received ICMP request packets to 
> update their ARP
> cache (on the basis that they will probably have to send 
> replies to the
> machine sneding the request and the ICMP packet has the needed data so
> that a separate ARP request would be waste of time).  
> 
> If you're lucky NT might be one of them.
> 
> Good luck,
> J.
> 
> 
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