Packet Switching Goals Reliability Speed Packet Switching Concepts

Packet Switching Goals • Reliability • Speed

Packet Switching Concepts • • • Break file into packets. Forward packets independently. Choose route for each packet. Reassemble packets at receiver. Present message to user.

File Partitioning Pretend this is a very long message that is to be partitioned for transmission over the internet from a source to a receiver. Break the message into segments. 1 2 Pretend_th is_is_a_ve 6 7 artitioned _for_trans 11 _a_source_ 12 to_a_recei 3 ry_long_me 8 mission_ov 4 5 ssage_that is_to_be_p 9 10 er_the_int ernet_from 13 er. _ _ _ _

Packet Transmission Pipeline Last | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | Next

Example Network (The network illustration is supposed to be complicated looking. ) Node A Node E Source Target Node B Node F Node C

Last | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | Next fast Node A Node E Source Target Node B Node F Node C 1 slow

Last | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | Next Received fast 2 Node A Node E Source Target Node B Node F Node C slow 1

Last | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | Next Received fast 2 Node A Node E Source Target Node B 3 Node F Node C slow 1

Last | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | Next 1 Received 2 fast Node A Node E Source Target Node B Node F 4 Node C 3 slow

Last | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | Next 2 | 1 Received fast 5 Node A Node E Source Target Node B Node F Node C slow 4 3

Last | 13 | 12 | 11 | 10 | 9 | 8 | 7 | Next Time on a link is not constant. 6 3 | 2 | 1 Received fast Node A Node E Source Node B Target 5 Node F Node C 4 slow

Last | 13 | 12 | 11 | 10 | 9 | 8 | Next 4 | 3 | 2 | 1 Received 6 7 fast Node A Node E Source Target Node B Node F Node C slow 5

Last | 13 | 12 | 11 | 10 | 9 | Next 6 | 4 | 3 | 2 | 1 Received 7 8 fast Node A Node E Source Target Node B Node F Node C slow 5

Last | 13 | 12 | 11 | 10 | Next 7|6|4|3|2|1 Received broken 8 Node A Node E Source Target Node B Node F 9 Node C slow 5

Last | 13 | 12 | 11 | Next 5|7|6|4|3|2|1 Received broken Node A Node E Source 8 Target Node B 10 Node F Node C slow 9

Last | 13 | 12 | Next 8 | 5 | 7 | 6 | 4 | 3 | 2 | 1 Received fast 11 Node A Node E Source Target Node B Node F Node C 10 slow 9

Last | 13 | Next 9 | 8 | 5 | 7 | 6 | 4 | 3 | 2 | 1 Received fast 12 Node A 11 Node E Source Target Node B Node F Node C slow 10

11 | 9 | 8 | 5 | 7 | 6 | 4 | 3 | 2 | 1 Received 12 fast 13 Node A Node E Source Target Node B Node F Node C slow 10

12 | 11 | 9 | 8 | 5 | 7 | 6 | 4 | 3 | 2 | 1 Received 13 fast Node A Node E Source Target Node B Node F Node C slow 10

13 | 12 | 11 | 9 | 8 | 5 | 7 | 6 | 4 | 3 | 2 | 1 Received fast Node A Node E Source Target Node B Node F Node C slow 10

10 | 13 | 12 | 11 | 9 | 8 | 5 | 7 | 6 | 4 | 3 | 2 | 1 Received fast Node A Node E Source Target Node B Node F Node C slow

Unscrambling 10 | 13 | 12 | 11 | 9 | 8 | 5 | 7 | 6 | 4 | 3 | 2 | 1 • Traditional • Streaming

Traditional • Reassemble after receiving complete message 10 | 13 | 12 | 11 | 9 | 8 | 5 | 7 | 6 | 4 | 3 | 2 | 1 • Present message to recipient 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13

Streaming • Example: Audio and video broadcast files. • Files viewed in “real” time. • Establish buffer to hold part of file received. • Display “Net congested” warning and delay replay if next file in sequence has not arrived yet.

Streaming Example Buffer 10 | 13 | 12 | 11 | 9 | 8 | 5 | 7 | 6 | 4 | 3 | 2 | 1 Listen Pretend this is a ve ry long message that is to be partitioned for transmission over the internet from a source to a receiver.

Buffer 10 | 13 | 12 | 11 | 9 | 8 | 5 | 7 | 6 | 4 | 3 | 2 | Listen Pretend th is is a very long me ssage that is to be partitioned for transmission over the internet from a source to a receiver.

Buffer 10 | 13 | 12 | 11 | 9 | 8 | 5 | 7 | 6 | 4 | 3 ry_long_me|ssage_that Listen Pretend this is a ve ry long message that is to be partitioned for transmission over the internet from a source to a receiver.

10 | 13 | 12 | 11 | 9 | 8 | 5 | 7 | 6 | 4 ssage_that|_ _ _|artitioned Pretend this is a very long me ssage that is to be p artitioned for transmission over the internet from a source to a receiver. 10 | 13 | 12 | 11 | 9 | 8 | 5 | 7 | 6 Need 5 next. Net congestion. |_ _ _|artitioned|_for_trans

10 | 13 | 12 | 11 | 9 | 8 | 5 | 7 | 6 Need 5 next. 10 | 13 | 12 | 11 | 9 | 8 | 7 | 6 | 5 Reorder packets. is_to_be_p|artitioned|_for_trans 10 | 13 | 12 | 11 | 9 | 8 | 7 | 6 artitioned|_for_trans 10 | 13 | 12 | 11 | 9 | 8 | 7 _for_trans|mission_ov

10 | 13 | 12 | 11 | 9 | 8 10 | 13 | 12 | 11 | 9 10 | 13 | 12 | 11 Need 10 next. Net congestion.

10 | 13 | 12 | 11 Need 10 next. 13 | 12 | 11| 10 13 | 12 | 11 13 | 12 13 Pretend this is a very long message that is to be partitioned for transmission over the internet from a source to a receiv er.