ECE 544 Project3

1. ECE 544 Project3 Anup Mathur Anusha Sheelavant Prakhar Srivastava

2. Assumptions • Assumptions • End hosts can only connect to routers • Same content available at multiple end nodes • All routers have static IP addresses • Routing tables are updated periodically and on events • Routers are allowed to send ACK’s for reliable transmission • Router can connect to a maximum 5 other routers and 254 hosts.

3. Address Scheme • Naming scheme and eventual address scheme • Router- R1,R2 .. R255 -- A.B.Rid.255 • End hosts- H1, H2 .. H255 -- A.B.Rid.Hid • Content- Filename Algorithm .

4. File name algorithm Hashing with variable data  Break the input into a sequence of small units (bits, byte, words, etc.) and combine all the units b[1], b[2], …, b[m] sequentially, as follows S ← S0; // Initialize the state. for k in 1, 2, ..., m do // Scan the input data units. S ← F(S, b[k]); // Combine data unit k into the state. return G(S, n) // Extract the hash value from the state. If b[k] are single bits, then F(S,b) could be if highbit(S) = 0 thenreturn 2 * S + b elsereturn (2 * S + b) ^ P Here highbit(S) - the most significant bit of S; the '*' operator denotes unsigned integer multiplication with lost overflow. '^' is the bitwise exclusive OR operation applied to words; and P is a suitable fixed word.

5. Content name • Content id: • Type: format ex: jpg,txt,mpeg • Hash table value The content name : type-hashvalue

6. Bootstrapping and Discovery • Algorithm • Routers and end hosts boot up (Hello packet?) • Discovery • Routers discover other routers • Hosts discover their router • Packet Format

7. Bootstrapping • Starting from router 0, connect router 1 • Handshake packets are sent – informing the other router about the presence. • Handshake packet contains the mac address and router id. • If no router id is maintained, then the router with lower mac address becomes the network start router. Assigning id :0(start) to itself and the next number in the series of 5.

8. Bootstrapping- Contd. • If the router is already connected to a network, it will allocate the next router its number based on the formula = id*5 +[1-5]. • If the router already has an id, no new id is allocated. • The routing table is built by using OSPF algorithm. • The Algorithm also conveys the content id. • If the router id is more than 255, then we use the 2nd octet of the Ip address. • If two networks are to be connected, the mac address defines the subnet and is assigned in the first octet of the ip address. • Each router then stores the mac address it was given and assigns itself the number given by the parent router.

9. Host id learning • Whenever a host connects to a router, the router assigns the ip address to the host as • A.B.Rid.Hid • As a consequence each router can be connected to only 255 hosts as the id 255 cannot be given. • The router maintains a table of the number of hosts connected, its sequentially assigned and the router maintains an alive table, which is refreshed with a timer overflow.

10. Hello Packet Identifier: HEL: Indicates that it is a “Hello” packet. ASN : assigning value ACK : Acknowledgement My Router ID: The ID of the sender. Guest Router ID: The ID of the router which is being assigned the ID. Device ID: ID which indicates whether the device is a router or a end Host. MAC Address: MAC Address of the sender.

11. Baseline Algorithm • Content routing algorithm • Updating the content library • Searching content • Content Host selection • Data transfer

12. Updating the content library • Host broadcasts the packet with : • Content id • Update Identifier • Broadcast Address • #of hops • At each router we forward to all nodes other than the source. • At each router we keep a copy of packet. • At each router we check if the number of hops is greater than the stored packet, discard. • If the router already has a copy with greater number of hops replace the copy and forward. • No acknowledgements are sent by the other host upon receiving the update- hosts update their content library.

13. Searching Content • Host broadcasts the packet with • Content id • Search Identifier • Broadcast Address • #ofhops • At each router we forward to all nodes other than the source. • At each router we keep a copy of packet. • At each router we check if the number of hops is greater than the stored packet, discard. • If the router already has a copy with greater number of hops replace the copy and forward. • The content provider sends an acknowledgement back to the source.

14. Content Host selection • At each router the packet with the lesser number of hops or smaller time is forwarded. • This removes the problem of cyclic transmission in broadcasting and also helps in selection of the acknowledgement. • The first acknowledgement received by the host is the path/source is chosen. • If two packets come at the same time, the acknowledgment with lower number of hops is considered.

15. Data transfer • Once the host receives an acknowledgement, a transfer packet is sent to the host selected. • The transfer packet should contain the destination address where the content was found. • Once the transfer packet is received, the content host starts making packets of the content and starts transmitting to the Receiving host. • In transit between the routers using Sliding window(selective repeat) algorithm with a window size of 4 packets and packet id of 3 bits

16. Data transfer • End of file: identifier tag is filled with EOF after the last data packet is sent, this closes the data transmission.

17. Data Transfer restrictions • No of hops> 255 discard. • Time to live for the copy is the N*x times the time stamp difference, for simplicity we are using the N=2. • In sliding window, if the acknowledgment is not received for length of sliding window time, an event for updating the routing table is made. • The time to live should be updated in the Selective sliding window if the acknowledgment is not received.

18. Data Transfer and Reliability • Message Forward • Multicast is not supported • Unicast: we need the destination address • Broadcast is supported for 255.255.255.255 • ARQ Scheme • Hop-by-hop – Sliding Window Sliding window uses selective request scheme

19. Packet Format • Identifiers can be • SEA (Search) • UPD (Update) • ACK (Acknowledgement) • REQ (Request) • DAT (Data) • EOF (End of file)

20. Acknowledgement packet

21. EOF packet

22. Advantages and Disadvantages • Scalable to other networks using the first octet of the IP address to define other networks if no gateway • Latency – we have tried to maintain a fast hoh-hop link state, thus using a sliding window ARQ. • Disadvantage: Does not support multicast

23. Appendix: Network Architecture • Refer to the following example scenarios for analysis purposes: Scenario 1: @host_H2: get (content_C3) H2 C1 C2 R5 C3 H1 R1 R2 R3 R4 H3

24. Appendix: Network Architecture Scenario 2: @host_H1: get (content_C2) C2 H2 C3 C1 C2 R5 C3 H1 R1 R2 R3 R4 H3

25. Appendix: Network Architecture Scenario 3: @host_H1: get (content_C1) H1 H2 H3 H4 C2 C3 C1 C1 C1