Fragment basic ques

Hi

I have some very basic doubt in fragmentation .
Lets say we have following scenario :

R1 ---------- R2 ------------R3------------R4

R1-R2 MTU 1500
R2-R3 MTU 800
R3-R4 MTU 400

Lets say pkt of 2000 bytes arrives at R1 . It splits in 1500 and 500 . Let
MF means "more fragments"

MF = 1 Fragment offset = 0
MF =1 Fragment offset = 1501

These are fields written in IP header

Now next link R2 -- R3

MF = 1 Fragment offset = 0 ( 0 to 800)
MF = 1 Fragment offset = 801 ( 801 to 1500)
MF = 1 Fragment offset 1501 ( 1501 to 2000)

Next link R3 - R4

MF = 1 Fragment offset =0 ( 0 to 400)
MF = 1 Fragment offset = 401 ( 401 to 800)
MF = 1 Fragment offset = 801 ( 801 to 1200 )
MF = 1 Fragment offset = 1201 ( 1201 to 1500 )
MF = 1 Fragment offset = 1501 ( 1501 to 1900 )
MF = 0 Fragment offset = 1901 ( 1901 to 2000 )

Please let me know if these calculation is correct ? Please guide where MF
will be 0 and 1 ..(which router)

Thnx
Happy

Blogs and organic groups at http://www.ccie.net
Received on Tue Sep 21 2010 - 09:12:26 ART