Link Fragmentation

[shabib.syed]

Here is the question,

If a 1500byte IP datagram goes out of router which is configured for link fragmentation at every 500 bytes, assuming the safe reachability of three fragments at its final destination, how many acknowledgements can I expect back at the origin ...is it just one or three of them?

Please help me with a brief explanation.

Thanks to all,

Regards,

Manoj

[mnaveen]

Hi Manoj,

When a packet gets fragmented, the fragments gets reassembled at the receiver (host computer and not the router) as one full packet again. It then checks for L4 info and accordingly sends one acknowledgement. Remember that unless the packet is fully reassembled, acknowledgements cannot be sent.

In your case, there will be 4 fragments since there is an overhead of 20 bytes for each fragment.

Hope that has cleared your doubts.

Naveen.

mnaveen@cisco.com

[shabib.syed]

Hello Naveen,

Thanks for your comments. Could anyone of you tell me what would be the case in the case of Link Fragmentation and Interleaving, ie, Layer 2 Fragmentation?

Regards,