The fixed part of the both TCP and IP header is 20 bytes. With options, they may go to 24 bytes.
With regards Kings On Fri, Nov 26, 2010 at 9:49 AM, Kamran Shakil <[email protected]>wrote: > > Bruno, TCP is 24 bytes, IP is 20 bytes. > > Take a look here : http://mike.passwall.com/networking/samplepacket.html > > > regards, > > Kamran Shakil > ITA NDC Operations Engineer > BS(CS) MCSE CGAdmin CCDA CCNA > CCNP CCDP CS-CFEDS CS-CIPCES > CS-CIPCCES CS-CWALANDS CCIE-Sec. > MidEast Data Systems LLC Oman > Cell: + 968 95804126 > Office: + 968 24576640 > http://www.mynameise.com/kamranshakil77 > > Confidentiality Warning: > "This message and any attachments are intended only for the use of the > intended recipient(s), are confidential, and may be privileged. If you are > not the intended recipient, you are hereby notified that any review, > retransmission, conversion to hard copy, copying, circulation or other use > of all or any portion of this message and any attachments is strictly > prohibited. If you are not the intended recipient, please notify the sender > immediately by return e-mail, and delete this message and any attachments > from your system." > > > > -----Original Message----- > From: [email protected] on behalf of Bruno > Sent: Thu 11/25/2010 8:42 PM > To: Kingsley Charles > Cc: [email protected] > Subject: Re: [OSL | CCIE_Security] Fragment offset > > I thought TCP header had 20byes > > > On Thu, Nov 25, 2010 at 12:38 PM, Kingsley Charles < > [email protected]> wrote: > > > Hi all > > For the given below example, the fragment offset in the second > packet should be 185 right? The TCP header has not been considered while > calcuating the offset in the given below example. > > Snippet from http://www.tech-faq.com/packet-fragmentation.html > > > > A Packet Fragmentation Example > > > If a 2,366 byte packet enters an Ethernet network with a default MTU > size, it must be fragmented into two packets. > > The first packet will: > > * Be 1,500 bytes in length. 20 bytes will be the IP header, 24 > bytes will be the TCP header, and 1,456 bytes will be data. > * Have the DF bit equal to 0 to mean "May Fragment" and the MF > bit equal to 1 to mean "More Fragments." > * Have a Fragmentation Offset of 0. > > The second packet will: > > * Be 910 bytes in length. 20 bytes will be the IP header, 24 > bytes will be the TCP header, and 866 bytes will be data. > * Have the DF bit equal to 0 to mean "May Fragment" and the MF > bit equal to 0 to mean "Last Fragment." > * Have a Fragmentation Offset of 182 (Note: 182 is 1456 > divided by 8). > > > > With regards > Kings > > _______________________________________________ > For more information regarding industry leading CCIE Lab training, > please visit www.ipexpert.com > > > > > > > -- > Bruno Fagioli (by Jaunty Jackalope) > Cisco Security Professional > > >
_______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com
