Re: [SCTP] clarification about HB.Max.Burst parameter

Hello Ashish,
 
Thanks for your prompt response.
The purpose of HB.Max.Burst is still not clear to me.
Let us take an example scenario. 
 
Suppose the peer to IUT has 2 interfaces IP-X and IP-Y RTO for IP-X is 1 sec. and for IP-Y is 2 sec.
HB.Max.Burst at IUT set to 2.
 
The IUT has sent the HBeat to IP-X & IP-Y and started the Retransmission-timer separately for IP-X (1 sec) and I-Y (2 sec)..
 
Both IP-X and IP-Y are not responding.
 
After 1 sec.
RTO expired for IP-X. 
As the HB.Max.Burst in 2, so IUT will send the HBeat to both, IP-X and IP-Y, on the expiry of RTO for IP-X alone.
 
Why SCTP needs to send the Heartbeat to IP-Y even if I have already sent an Heartbeat to IP-Y for which Retransmission timer is already running?
Here, the retransmission timer for IP-Y will take 1 more second to expire.
 
Also, if IUT sends the Heartbeat to IP-Y on the RTO expiry of IP-X then will it restart the RTO timer for IP-Y?
 
Please clarify as I am not able to understand the benefit of making HB.Max.Burst > 1.
 
Thanks & Regards,
Ashwani Kathuria
----- Original Message ----
From: Ashish Gupta <[email protected]>
To: Ash Kat <[email protected]>; [email protected]; [email protected]
Sent: Wednesday, 4 June, 2008 3:39:00 PM
Subject: RE: [Sigtran] [SCTP] clarification about HB.Max.Burst parameter


Hi Ashwani,
 
When RTO expires for an address, your path probing module will get chance to send HEARTBEATS to other UNCONFIREMD addresses as well (NOT only to the address for which RTO has expired) limited by HB.Max.Burst parameter.
 
Hope this helps.
 
Regards,
-Ashish
 

________________________________

From:[email protected] [mailto:[email protected]] On Behalf Of Ash Kat
Sent: Wednesday, June 04, 2008 3:14 PM
To: [email protected]; [email protected]
Subject: [Sigtran] [SCTP] clarification about HB.Max.Burst parameter
 
Hello All,
 
SCTP RFC 4690 has mentioned a parameter HB.Max.Burst.
As per RFC 4960 section 4..5 :
   The number of HEARTBEATS sent at each RTO SHOULD be limited by the
   HB.Max.Burst parameter.
 
During the Path verification when an RTO expires, SCTP will re-send the Heartbeat to that address.
Please clarify me, how HB.Max.Burst parameter will control the number of Heartbeat sent to that address.
Shouldn't the number of Heartbeat send to a particular address at any time will always be 1? 
If Yes, then why HB.Max.Burst is required?
If No, then please make me understand that how this parameter is used.
 
Thanks & Regards,
Ashwani Kathuria



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