This is a repository for my computer networks course assignment 1, I completed during the course of METU EE444 Introduction to Computer Networks in 2021-2022 Spring Semester.
This assignment's instructions credit to Middle East Technical University - Electrical - Electronics Engineering Department and METU EE444 Introduction to Computer Networks Course Lecturers.
Figure 1 - Layered Network Architecture
Figure 2 - State Diagram of TCP Sockets
For this homework, you will implement a simple system consisting of 3 nodes. Namely, Client, Proxy and Server. Topology is very simple and can be seen in Figure 3.
Figure 3 - Topology of the Network
The Server will hold a list of 10 elements as described in Table 1. Each entry will consist of an index value ranging from 0 to 9 and data of a single integer. The Proxy should be consistent with the server, that is any update made to the Proxy's table should also be made in Server's table.
The Proxy server will hold half of the table in its process as described in Table 2, think of it as a cached version of the Server's table. The Client will only communicate with the proxy server, if an element that is not present in the Proxy's table is required proxy server will communicate with the Server to get that element and add it to its table by overwriting the oldest table entry.
Nodes will exchange proxy messages between them with the format as below.
OP=XXX;IND=Ind1,Ind2,..;DATA=Dat1,Dat2,...;
Notice that fields are separated with semicolons(;). OP field describes which operation to do on the table, for more detail check Table 3. IND field tells which of the indexes are required for the operation. The DATA field is for integer data either from the server for operations like "ADD" or as an update value from the client. Not all messages require every field. You can choose to omit the unused fields for certain operations. Details of the implementation are up to you.
Response messages have the same form as request messages. For example response of the "ADD" message will have "ADD" as the operation code and contain the result in the "DATA" field.
