Assignment 4 - Client - Server

1.    What is a Client-Server?
-  Client-server is an architecture used for networking.
-  A common form of system which software is split between server task and client task
-  Usually at least a manager(server) and an agent(client) had set up in the network


2.     How does it work?
-   All client-server protocols operate in application layer.
-   Server are the processes dedicated to managing the server and the clients are the workstation which run the applications.
-   Client will report an event to the server and the server will do something either to response to the client or nor.

3.     Why is a Client-Server Network good?
-   Client-Server Network is centralization,Server help in administering the network.Access right is done by servers.
-   Comes with proper management. The file easy to find out because all files are stored at the same place.
-   Back-up and recovery possible
-   Accessibility, server can be accessed remotely.
-   Security, rules defining security and access right can be defined at the time of set-up server
server can play different roles for different clients

4.   What are the drawbacks to the Client-Server Model?
-   Congestion in network. too mnay request from the clients may lead to congestion
-   Client-server architecture is not as robust as peer-to-peer
-   Expensive to install and manage

5.     What correlation the thin and thick client to this topic?
Thin Clients
- Easy to deploy as they require no extra or specialized software installation
- Needs to validate with the server after data capture
- If the server goes down, data collection is halted as the client needs constant communication with the server
- Cannot be interfaced with other equipment (in plants or factory settings for example)
- Clients run only and exactly as specified by the server
- More downtime
-Portability in that all applications are on the server so any workstation can access
- Opportunity to use older, outdated PCs as clients
- Reduced security threat

Thick Clients
- More expensive to deploy and more work for IT to deploy
- Data verified by client not server (immediate validation)
- Robust technology provides better uptime
- Only needs intermittent communication with server
- More expensive to deploy and more work for IT to deploy
- Require more resources but less servers
- Can store local files and applications
- Reduced server demands
- Increased security issues

Task 3: TCP vs. UDP

TCP and UDP are two different protocols which both can handle data communications between terminal through an Internet. In OSI model, both protocols are classified as Transport Layer Protocols.

TCP (Transmission Control Protocol)

>> Connection-oriented protocol

>> Suitable for applications that require high reliability, and transmission time is relatively less critical

>> Function as a message makes its way across the internet from one host to another host

>> Use by other protocols such as HTTP,HTTPs,FTP,SMTP,Telnet

>> Rearranges data packet in order specified

>> Speed slower than UDP

>> Reliability

>> Header size : 20bytes

>> TCP does error checking

>> Acknowledge segments

UDP (Universal Datagram Protocol)

>> Connectionless protocol

>> Used in message transport transfer

>> Suitable for application that need fast, efficient transmission

>> Use by other protocols such as DNS.DHCP,SNMP and etc

>> Has no inherent order as all packet are independent of each others

>> Speed UDP is fast because there no error-checking for packets

>> No reliability

>> UDP header size: 8 bytes

>> Do not need acknowledgement

Task 2: Briefly describe the process of sending packets from Host A to Host D

The transmission would go like this:

Host A wants to send a packet to Host D. Host A must knows Host D's IP address. However, if it does not know, then it will send something called an ARP request (Address Resolution Protocol) to the network, with the destination IP. 

 A few things will happen here:

1. If the IP is local. The host with that IP will reply back to the sender with its MAC address.
2. If the IP is non-local. The gateway router will detect this and send its MAC address.
3. If the IP is non-local and Host A's default gateway and subnet mask are set. Using this information Host A can determine the non-locality of the IP address and send it to the router's MAC address (ARPing if not known yet).

If Host A found this out earlier, it will be in the ARP cache and Host A will just use that. Now that the MAC address is sent, the packet can be transferred. The next stop will be the hub. The hub knows which outbound port the MAC address listed as the destination is on, because it tracks every MAC address it's seen a packet come from and which port it came on, If it does not know, then it will flood it out every single port, guaranteeing it'll arrive.

As such, the packet arrives at the router. The IP model is that it divides every single IP address in the network/world into a hierarchy which is subnet. The packet is then sent out that port.

Task 1 : List all the dial-up modem speed ( Connection VS Bitrate )

Figure below shows the list of dial-up speed and the bitrate

The values given are maximum values and actual values may be slower under certain conditions such as noisy phone lines.

Figure above shows that the connection with its modulation, bitrate and year released.