[dhcwg] RFC 3315 message re-transmission query

[ravi kumar <ravikumar.lrk at gmail.com>]

Thanks a lot to people in forum for promptly answering my queries.

I have one more query regarding calculation of Retransmission time-out in Section-14 of RFC 3315:

 

 RT for the first message transmission is based on IRT:

      RT = IRT + RAND*IRT

   RT for each subsequent message transmission is based on the previous
   value of RT:

      RT = 2*RTprev + RAND*RTprev

 

Do RTprev value used in subsequent calculation of RT, include randomization added by RAND ?

I guess should not be the case, because the retransmission algorithm is exponential back-off algorithm and incase RAND is added multiple levels in calculation of RT,this exponential nature is lost.

I have done simple Math in calculating maximum and min waittimes for REQUEST message, by considering "RTPrev includes RAND" :

0.9 ---   1.1  
1.711 --- 2.31
3.249 --- 4.851
6.1731 -- 10.1871
11.72889 --- 21.39291
22.284891 --- 44.925111                            -> The time difference here is very large here

 

I consider Retransmission wait times to be exponential wait times, with randomization factor included to minimize synchronization of messages transmitted by DHCP clients. In that case, calculation of RT should involve RTPrev (without Random factor) + Random factor.

 

Please correct me if I am wrong in my assumption.

 

regards

Ravi