Internet Protocol Functions

11 Fragmentation and Reassembly (Segmentation – OSI) Exchange data between two entities Characterized as sequence of PDUs of some bounded size — Application level message Lower-level protocols may need to break data up into smaller blocks Communications network may only accept blocks of up to a certain size — ATM 53 octets — Ethernet 1526 octets More efficient error control — Smaller retransmission Fairer — Prevent station monopolizing medium Smaller buffers Provision of checkpoint and restart/recovery operations Disadvantages of Fragmentation Make PDUs as large as possible because — PDU contains some control information — Smaller block, larger overhead PDU arrival generates interrupt — Smaller blocks, more interrupts More time processing smaller, more numerous PDUs Reassembly Segmented data must be reassembled into messages More complex if PDUs out of order PDUS and Fragmentation (Copied from chapter 2 fig 2.4) Connection Control Connectionless.

Communications network may only accept blocks of up to a certain ______

Lower-level protocols may need to break data up into smaller ______

More efficient error control — Smaller ______

More complex if PDUs out of ______

Segmented data must be reassembled into ______

Fragmentation and Reassembly is part of which layer of the OSI model?

Communications network may only accept blocks of up to a certain ______

Make PDUs as large as possible because — PDU contains some control ______

Connection Control and Connectionless are types of ______