ECE 544 Protocol Design Project Team Member Names Aneesh Abhyankar Satakshi Tiwari Vishalsingh Hajeri

Transcription

1 ECE 544 Protocol Design Project 2016 Team Member Names Aneesh Abhyankar Satakshi Tiwari Vishalsingh Hajeri

2 Network Architecture & Topology Assumptions Service Objective: k-out-of-n packet datagram multicast Assumptions Unreliable network with packet loss prob. per link of p Each end node is attached to only one router All links have same characteristics (i.e. hop cost 1 and same MTU 1500 bytes). So, distance will be equal to the number of hops Small maximum number of routers (i.e. 50 to 100) n = 3 and k <= 3 (k will be chosen by the sending host) Hosts will have unique 8bit addresses and will be configured using a static allocation table

3 Protocol Concept Overall concept of our proposed protocol The Application layer will decide which three hosts (since n=3) it wants to send packets to. It will also decide the value of k (k <= 3) If k=2 (say), then the routes will figure out which two hosts among the three are the least costly using routing tables. The packet will therefore have: Three addresses of probable destination hosts Value of k (k <= 3) Source Address Header Length, Packet Length (as delimiters) Data All addresses are assumed to be of 1 byte, i.e. 8 bits

4 Syntax Packet Formats Data Packet Control Packet Hello/Ack Packet

5 Semantics Control Packet Hello/Ack Packet Flag if 0=>It is a hello packet (broadcast and therefore ignore the dest address) if 1=>It is an ack packet (unicast and therefore dest address comes into play) Data Packet Type if 0=>It is a data packet if 1=>It is a control packet

6 Routing Algorithm 1. Initialize the Confirmed list with an entry for myself and a cost of For the node just added to the Confirmed list in the previous step, call it node Next, select its LSP. 3. For each neighbor (Neighbor) of Next, calculate the cost (Cost) to reach this Neighbor as the sum of the cost from myself to Next and from Next to Neighbor. (a) If Neighbor is currently not on either the Confirmed or the Tentative list, then add (Neighbor, Cost, NextHop) to the Tentative list, where NextHop is the direction I go to reach Next. 4. If the Tentative list is empty, stop. Otherwise, pick the entry from the Tentative list with the lowest cost, move it to the Confirmed list, and return to step 2

7 Data Plane Forwarding Each router will have multiple paths (at the most equal to the number of neighbors) to reach each destination It has to select best two out of three It will look at each option and figure out possible path overlap between two destinations It will also look at path costs of these options If k=2, it will calculate make the following calculations

8 Data Plane Forwarding Overlapping Paths Destination 1 & 2 =>cost=a Destination 1 & 3=>cost=b Destination 2 & 3=>cost=c Non-overlapping Paths Destination 1 & 2 =>cost=d Destination 1 & 3=>cost=e Destination 2 & 3=>cost=f The router will now select the least cost destinations and send it to them It will also eliminate the third destination address from the packet header, so that other routers know that they don t have to select two out of the three again

9 Link State Routing Protocol

10 SPF to D1 from S R2 R6 D1 S R1 R3 R7 R5 R4 R8 D2

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14 Cost = 4

15 SPF to D2 from S

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20 Cost = 5 R2 R1 R6 D1 S R3 R7 R5 R4 R8 D2

21 Table at the First Router Overlapping Paths Destination 1 & 2 =>cost=7 Non-overlapping Paths Destination 1 & 2 => cost=3+4 = 7 Table at the Second Router Overlapping Paths Destination 1 & 2 =>cost=5 Non-overlapping Paths Destination 1 & 2 => cost=3+3 = 6 Table at the Third Router Overlapping Paths Destination 1 & 2 =>cost= Non-overlapping Paths Destination 1 & 2 => cost=2+2 = 4

22 Sending via common Path R2 D1 S R1 R3 R4 D2

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25 R7 duplicate packet at R7

26 Duplicating the packet

27 Cost = 7

28 Network 1 R1 R2 R3

29 Table at the Router R1 Overlapping Paths Destination D1 & D2 =>cost=6 Destination D1 & D3=>cost=6 Destination D2 & D3=>cost=5 Non-overlapping Paths Destination D1 & D2 =>cost=7 Destination D1 & D3=>cost=7 Destination D2 & D3=>cost=10 R1 will select destinations D2 and D3 and forward packets via the overlapping path, since it finds the cost to be minimum It will also delete the address of D1 from the packet header so that the subsequent routers know that the two destinations are D2 and D3

30 Summary Key protocol design features (recap) Uses Link State Routing Protocol Instead of eliminating high cost paths, it saves them as well Implementation Complexity Cost of storing the routing table Number of destinations * Number of Neighbors