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<FONT face=Tahoma size=2><B>From:</B> end2end-interest-bounces@postel.org
[mailto:end2end-interest-bounces@postel.org] <B>On Behalf Of </B>Saqib
Ilyas<BR><B>Sent:</B> Wednesday, April 11, 2007 12:33 AM<BR><B>To:</B>
end2end-interest@postel.org<BR><B>Subject:</B> [e2e] iBGP session
break<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV>Greetings everyone</DIV>
<DIV>My question is: Is it possible for an iBGP session to break even when the
underlying IP topology is not partitioned? </DIV>
<DIV>We would expect that IGP maintains connectivity at the IP layer, and even
in case of a failure in the network that doesnt partition the topology, the
IGP should be able to quickly converge to a new configuration for paths
between every possible pair of nodes. This should result in, perhaps, a
few dropped TCP packets for the iBGP session, but not a session break. Would
it, then still be possible for an iBGP session to break and blackholes to
consequently result?<SPAN class=796221018-11042007><FONT face=Arial
color=#0000ff size=2> </FONT></SPAN></DIV>
<DIV><SPAN class=796221018-11042007><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=796221018-11042007><FONT face=Arial color=#0000ff size=2>It
is certainly possible depending on the configuration. BGP uses
hold and keep-alive</FONT></SPAN></DIV>
<DIV><SPAN class=796221018-11042007><FONT face=Arial color=#0000ff
size=2>timers. If a session has its hold timer expire
because of not receiving a keepalive</FONT></SPAN><SPAN
class=796221018-11042007><FONT face=Arial color=#0000ff size=2>, then
</FONT></SPAN></DIV>
<DIV><SPAN class=796221018-11042007><FONT face=Arial color=#0000ff
size=2>the session will be terminated, even though TCP would not
</FONT></SPAN><SPAN class=796221018-11042007><FONT face=Arial color=#0000ff
size=2>normally have torn down </FONT></SPAN></DIV>
<DIV><SPAN class=796221018-11042007><FONT face=Arial color=#0000ff size=2>the
connection on its own. </FONT></SPAN></DIV>
<DIV><SPAN class=796221018-11042007><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=796221018-11042007></SPAN><SPAN
class=796221018-11042007><FONT face=Arial color=#0000ff size=2>In the typical
case (hold timer 180 sec, keep alive timer 60 sec), you probably
</FONT></SPAN></DIV>
<DIV><SPAN class=796221018-11042007><FONT face=Arial color=#0000ff
size=2>wouln't lose the peering while the IGP is reconverging. But if
these timers</FONT></SPAN></DIV>
<DIV><SPAN class=796221018-11042007><FONT face=Arial color=#0000ff size=2>are
set very low, then you might.</FONT></SPAN></DIV>
<DIV><SPAN class=796221018-11042007><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=796221018-11042007><FONT face=Arial color=#0000ff
size=2>Anoop</FONT> </SPAN></DIV></BLOCKQUOTE></BODY></HTML>