Subject: doubt :Regarding buffer_size of encapsulation field .

From: Prashant Vedantam <[email-masked]>
Date: Thu, 15 Apr 1999 16:59:22 +0530

Now say that we have an IP packet of size = 1200 bytes .

This IP packet is fragmented into 3 fragments each of 400 bytes .

we have 3 cases :

1)please tell which case is the one which you are supporting .

2)If possible throw some light on 1394 packet header info which you were

talking about (no thing has been mentioned in the draft as such ).

-------------------------------------------------------------------------

case 1: (BUFFER_SIZE = size of the fragmented IP packet )

Now the  fragments will have the encapsulation header
format with the following fields set

(HERE I HAVE ONLY TAKEN THE FIELDS WHICH ARE IMPORTANT TO GET THE DOUBT
CLEARED)

 first fragment :
        lf = 1 (first )
        buffer_size = 400

second frgament
        lf = 3  (interior fragment )
        buffer_size = 400
        fragment offset = 401

third fragment:
        lf = 2 (last fragment)
        buffer_size = 400
        fragment offset = 801

----------------------------------------------------------------------
case 2: ( BUFFER_SIZE = SIZE OF THE ENTIRE IP PACKET )

first fragment :
        lf = 1
        buffer_size = 1200

second frgament :
        lf = 3
        buffer_size = 1200
        fragment offset = 401
third fragment :
        lf = 2
        buffer_size = 1200
        fragment offset = 801

--------------------------------------------------------------
case 3: (BUFFER_SIZE = SIZE OF THE TOTAL FRAGMENTS YET TO COME)

first fragment :
        lf = 1
        buffer_size = 1200
second fragment :
        lf = 3
        buffer_size = 800
        fragment offset = 401
third fragment :
        lf = 2
        buffer_size = 400
        fragment offset = 801

------------------------------------------------------------

P.vedantam
Design and development
TATA ELXSI LIMITED
Bangalore