Project 5 Soumya Basu Department of Computer Science Cornell - - PowerPoint PPT Presentation

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Project 5 Soumya Basu Department of Computer Science Cornell - - PowerPoint PPT Presentation

Jan 24, 2024 141 likes •389 views

Project 5 Soumya Basu Department of Computer Science Cornell University September 18, 2015 Administrivia Project 5 is due on November 18 Will be implementing a Link State routing protocol The Five Parts Connecting two nodes

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SLIDE 1

Project 5

Soumya Basu Department of Computer Science Cornell University September 18, 2015

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SLIDE 2

Administrivia

  • Project 5 is due on November 18
  • Will be implementing a Link State routing protocol
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SLIDE 3

The Five Parts

  • Connecting two nodes
  • Dijkstra’s algorithm
  • Flooding
  • Link State Routing
  • (Optional) Application!
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SLIDE 4

Part 0

  • Read the skeleton code
  • You will need to interact with most of it
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SLIDE 5

Connecting two nodes

  • Need to read up on the socket API calls
  • Important functions:
  • socket, fcntl, setsockopt, bind
  • Use man pages to see the options
  • Not many lines of code
  • Format: C<IPaddr:port>
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SLIDE 6

Dijkstra’s Algorithm

5 8 1 5 3 2 7 infty infty infty infty

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SLIDE 7

Dijkstra’s Algorithm

5 8 1 5 3 2 7 5 infty 8 1

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SLIDE 8

Dijkstra’s Algorithm

5 8 1 5 3 2 7 5 infty 8 1

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SLIDE 9

Dijkstra’s Algorithm

5 8 1 5 3 2 7 5 4 6 1

Because 6 < 8

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SLIDE 10

Dijkstra’s Algorithm

5 8 1 5 3 2 7 5 4 6 1

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SLIDE 11

Dijkstra’s Algorithm

5 8 1 5 3 2 7 5 4 6 1

Because 6 < 4+7

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SLIDE 12

Dijkstra’s Algorithm

5 8 1 5 3 2 7 5 4 6 1

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SLIDE 13

Dijkstra’s Algorithm

5 8 1 5 3 2 7 5 4 6 1

Because 4 < 5 + 2

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SLIDE 14

Dijkstra’s Algorithm

5 8 1 5 3 2 7 5 4 6 1

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SLIDE 15

Dijkstra’s Algorithm

5 8 1 5 3 2 7 5 4 6 1

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SLIDE 16

Flooding

  • How do you figure out the link state?
  • Broadcast!
  • You only have point-to-point though…
  • Gossip protocol
  • G<srcIP:srcPort>/counter/payload\n
  • Payload will change
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SLIDE 17

Flooding

  • Naive implementation:
  • When you hear a message, tell EVERYONE!

B A C B A C

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SLIDE 18

Flooding

  • Broadcast storms are not good…
  • We make two optimizations:
  • Don’t tell the person that sent you the message
  • Don’t spread around messages you’ve seen

already

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SLIDE 19

Flooding

B A C

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SLIDE 20

Flooding

B A C

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SLIDE 21

Flooding

B A C

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SLIDE 22

Flooding

  • Can we do even better?
  • Yes, but this is good enough!
  • What to flood?
  • Your connection state every time it changes
  • A new connection, a dead connection, etc.
  • Gossip payload: “;<addr1:port1>;<addr2:port2>…”
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SLIDE 23

Link State Routing

  • You have most of the pieces already!
  • When you see a message, send it along the

Dijkstra tree

  • Most of the work here is the send message

implementation

  • Send format: S<dstIP:dstPort>/TTL/payload\n
  • Make sure to decrement TTL
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SLIDE 24

Optional Applications

  • Mapping IP addresses to names (DNS)
  • Anything else you want!