ECE 544 Protocol Design Project 2016 Ashish Behl Shreyas Bhandare

Network Architecture & Topology Assumptions Service Objective: k-out-of-n “packet datagram” multicast – explain network service exactly, use a figure 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) Small maximum number of nodes (i.e. 50) Additional Assumptions: Host(256) addressing – static (0 – 255) 8 bit addressing Routers(50-100) – static addressing. All elements on same network, no gateways. No directly connected hosts.

Protocol Concept Overall concept of proposed protocol Routing Protocol – Modified Routing Information Protocol ( a distance vector routing protocol ) ARQ Protocol - Stop and Wait (easy to implement) Data forwarding algorithm – Based on hop counts as well as maximum common route for <=k nodes. Types of Packet: ‘hello’ packet, Routing Update Packet, data packet, ACK packet

Syntax – Packet Formats Routing Update Packet Data Packet ACK Hello Packet:

Semantics Routing Update Packet: Each Router sends this packet to its neighbors with its routing table information. Data Packet: Actual Data packet with payload and fragmented data. Ack Packet: Acknowledgement for Routing Update Packet and cumulative acknowledgement for data packet. Hello Packet: To check healthiness of neighbor. This packet will be broadcasted from every node with 10 secs time interval.

Routing Algorithm Similar to RIP Each router will periodically send Routing Update Packet to its neighbors until the routing table converges. This packet will have a routing table which will update its neighbors routing table by comparing both tables. The link cost will now be hop counts in this condition. Periodic time will be 15 seconds for this routing packet. (arbitrarily chosen as original RIP is slow and has 30 sec). At each node and host Routing table will consist of ‘k’ destination address minimum hop counts to those address.

Data Plane Forwarding If k =1, Find the best minimum hop count path forward the packet. If k=2, Calculate p1 = sum of costs to each destination having common next hop – 1 (which is total worst case hop cost of sending to k with only the next hop being common). Calculate p2 = sum of costs to each destination with diverging next hops. If p1<=p2, choose the common next hop, else choose the diverging destinations.

Example Networks: For k=1, Forward packet randomly to either d1,d2,d3 Destination Hop count Next Hop D1 3 R2 4 R4 5 R6 D2 D3 For k=1, Forward packet randomly to either d1,d2,d3 For k=2, Forward packet randomly to one of the combinations of d1-d2 d2-d3 or d3-d1 For k=3, Forward packet to all three d1,d2,d3

Example Networks: Network 2 R1 Destination Hop count Next Hop D1 3 R4 6 R4 Destination Hop count Next Hop D1 2 R3 D2 3 R5 D3

Example 2 continued... For k =1, Forward packet to d1 For k=2, Forward packet to d2 and d3 (common path and diverge) For k=3, Forward packet to d1, d2, d3.

Summary Key protocol design features (recap) Protocols: RIP, Stop and Wait, Maximum common path forwarding algorithm. Performance Simplicity of RIP makes routing easy. Delay is more because of RIP routing convergence. Less overheads because of smaller packet size. Cumulative ack may help reducing overhead.