ECE 544 Protocol
Design Project 2016
Ashish Behl
Shreyas Bhandare
Network Architecture & Topology
Assumptions
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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:
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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
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Overall concept of proposed protocol
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Routing Protocol – Modified Routing Information Protocol
( a distance vector routing protocol )
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ARQ Protocol - Stop and Wait (easy to implement)
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Data forwarding algorithm – Based on hop counts as well
as maximum common route for <=k nodes.
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Types of Packet: ‘hello’ packet, Routing Update Packet,
data packet, ACK packet
Syntax – Packet Formats
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Routing Update Packet
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Data Packet
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ACK
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Hello Packet:
Semantics
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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
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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.
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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).
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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:
Network 1
R1
Destination
Hop count Next Hop
D1
3
R2
D1
4
R4
D1
5
R6
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
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D2
3
R4
D2
4
R2
D2
4
R6
D3
3
R6
D3
4
R4
D3
5
R2
Example Networks:
Network 2
R1
Destination
Hop count
Next Hop
D1
3
R4
D1
3
R2
D2
4
R4
D3
4
R4
D2
6
R2
D3
6
R2
Destination
Hop count
Next Hop
D1
2
R3
D2
3
R5
D3
3
R5
R4
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.
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Summary
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Key protocol design features (recap)
Protocols: RIP, Stop and Wait, Maximum
common path forwarding algorithm.
Performance
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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.