Analyzing Network Protocols of Application Layer Using Hidden Semi-Markov Model

Algorithm 1

Closed frequent string algorithm.

(1)   Input: observation , frequency threshold

(2)   Output: closed frequent string set

(3)  # Find out the frequent strings

(4)   Initialization: frequent candidate set ,

(5)   while    do

(6)   # Check frequency of strings in

(7)   for    do

(8)    # is the frequency of in

(9)    if    then

(10)     Delete from

(11)      end if

(12)    end for

(13)    # Generate new candidate set

(14)    for    do

(15)    if    then

(16)     Create a new string

(17)     Let ,

(18)     Add to

(19)    end if

(20)   end for

(21)   ;

(22)  end while

(23) # Find out the closed frequent strings

(24)  Initialization:

(25)  while    do

(26)   for    do

(27)    for    do

(28)     # delete the substrings

(29)     if    then

(30)      Delete from

(31)       Break

(32)     end if

(33)    end for

(34)   end for

(35)   Update

(36)  

(37)  end while

(38)  Update