ECE 544 Project 3 Content Based Routing

Neelakantan Nurani Krishnan

Shikha Kakkar

Suja Srinivasan

Assumptions and Address Scheme

Assumptions Each end-host can connect only to one router. Same content may be available at multiple end-

hosts. The next ‘best-hop’ is selected based on the hop

count – the smaller, the better. The links connecting the different network

elements might be lossy (loss probability p). A host can request for multiple contents at a

time.

Assumptions and Address Scheme Assumptions (Continued)

Content locations are dynamic (they change over time).

Number of hosts connected to the network and different content are both less than 255.

Addressing Scheme Routers – identified as 1,2,…. End host IDs are not required in our design Content – identified with the content IDs (0-255)

Bootstrapping and Discovery Algorithm

After boot-up, each end-host will intimate its default router about the content that it has. This information will be propagated throughout the network by the routers.

When a router gets a packet with a certain Content ID for the first time, it will make an entry for that ID in its forwarding table.

If a router receives an update packet for a Content ID for which it already has an entry in its forwarding table, it compares the two hop counts and chooses the one with the smaller value.

Bootstrapping and Discovery Algorithm (Continued)

Update packets, containing information about the content of a end-host, will be sent periodically by each end-host to its default router (as content locations can change).

Update packets will also be triggered when the content advertisement by a host changes (addition/deletion) Every content will have a flag which will identify

whether the received content can be re-advertised by the receiver.

Routing Algorithm Baseline Algorithm

Each router has two tables – Forwarding Table (FT) and Pending Request table (PRT).

An end-host interested in a certain content sends a ‘Request Packet’ to its default router with the desired Content ID. The latter creates an entry in its PRT corresponding to this request and forwards the request based on FT.

The end-host with the desired content gets the request from its default router and prepares a ‘Response Packet’ containing the Content and the Content ID.

Routing Algorithm

Baseline Algorithm (Continued) The Request Packet propagates through the

routers based on FT entries and reaches the source of the content.

Example Forwarding Table Content ID Interface to

send req.No. Of Hops

2 4 1

1 2 2

4 1 1

* * *

* * *

Routing Algorithm Baseline Algorithm (Continued)

The Response Packet propagates through the routers based on PRT entries and reaches the requesting host.

Example Pending Request Table

Content ID OutgoingInterface

2 4

1 5

4 1

* *

* *

Packets Request Packet

TYPE – Type of Packet (2 bits)

CONTENT ID – Uniquely identifies a content (8 bits)

Response Packet

TYPE – Type of Packet (2 bits)

FLAG – Indicates re-advertisement (1 bit)

CONTENT ID – Uniquely identifies a content (8 bits)

CONTENT – Contains the actual content/payload (<1466 Bytes)

TYPE CONTENT ID

TYPE FLAG CONTENT ID CONTENT

Packets (Continued)

Update Packet

TYPE – Type of Packet (2 bits)

CONTENT ID – Uniquely identifies a content (8 bits)

Number of Hops – Number of Hops to reach the Content identified by CONTENT ID (8 bits).

TYPE CONTENT ID Number of Hops

Data Transfer and Reliability Message Forward

The ‘Discovery/Update’ packets will be forwarded through all interfaces except the incoming interface.

The ‘Request/Response’ packets will be forwarded based on the entries in FT & PRT.

ARQ Scheme End-to-End owing to its simplicity.

Example Scenarios

H1

H2

H3

C1

C2

C2

C3

C3

R1 R2 R3 R4

R5

Scenario 2: @host_H1: get (content_C2)

Scenario 2: @host_H1: get (content_C2) : Forwarding Tables

ID PORT HOPS

C1 1 0

C2 2 2

C3 2 2

ID PORT HOPS

C1 1 1

C2 3 1

C3 3 1

ID PORT HOPS

C1 1 2

C2 2 1

C3 2 1

ID PORT HOPS

C1 1 3

C2 2 0

C3 2 0

ID PORT HOPS

C1 2 2

C2 1 0

C3 1 0

R1 R2 R3

R4 R5

Scenario 2: @host_H1: get (content_C2) : Pending Request Tables

ID PORT

C2 1

ID PORT

C2 2

R1 R2

ID PORT

C2 1

R5