Need help! Consider an example scenario where you want to send some merchandise

Question

Need help!

Consider an example scenario where you want to send some merchandise to your friend living in another city (the kind of friend and the kind of merchandise doesn't matter). You need to answer the following questions:

Example: For instance, we can have local post offices, regional post offices and some global delivery services. Their contracts are based on the amount of merchandise they send and receive.

d) Where the layers would be implemented (end-system, packet switches or both)? Discuss how the intermediate systems would process the parcels from source to destination? Again, make reasonable assumptions.

e) At the application layer, what are the things we can do to our merchandise? Should we use some protocol? Would this protocol be only implemented at the sender side?

f) In reference to the transport layer, we have TCP and UDP on the internet. Relate the basic services provided by them to our example. Which protocol should we use?

g) Explain and relate the concepts of IP addresses, MAC addresses, Sockets, Port numbers and Processes with our example scenario.

h) You need to explain and relate the application architectures, Client Server and the Peer-to-Peer for the merchandise delivery. Make reasonable assumptions where needed.

Explanation / Answer

d)

The implementation of the post office can be related with the implementation of the global internet service. The packets of data or the data blocks which we share, send or recieve over the internet can be thought of as parcel which we have to send to the different location on the planet.

When we have to post any parcel to somewhere in the world our task is to post the parcel at the local post office nearest to our residing place. In the same way when we have to send the packet throught the local internet service provider who has actually provided us with the internet service. He is termed as the Access ISP.

Now when the parcel is given to the local post office, they forward it to the regional post office of that area. This is the place where all the parcels from all the local post offices of that region comes and they monitors the parcels are forwards them further to the global post office of the country from where the parcel is sent In the same way the local ISPs or the Access ISP uses the network of the regional ISP and the packet they have recieved is further sent to the regional ISP for further routing the packet towards the destination address of the packet.

There are some global ISPs who have connected all the continents by laying the fiber cabels between the contenents inside the oceans. Companies like AT&T, Sprint, etc are the global ISPs. The the parcel is exchanged glabally between the global post offices. Analogous to the post office scenario, the packet is also exchanged between the global ISPs.

As we have moved up in the ladder on the sender's side, similarly now we have to climb down the ladder on the reciever's side. From global ISP to regional ISP , from there to the local ISP and from there to the customer's destination.

e)

Using the application layer we atually get the data which is to be sent to the distant location. For example the Simple Mail Transfer Protocol works at the application layer is used to share the emails between the users of the application and we have the send the email data to the different user. When it comes to our merchandise yes we can apply some of the application properties to it. Like one person have to send a letter to the other user. In this scenario both of the persons must have a common language between them using which they are communicating with each other by sending the letter. This set of rules which are common to both of the end users is known as the protocol. This set of rules defines the way how the reciever of the packet or the parcel is going to user the data that is contained in it. Yes the set of protocols applied at the sender's end must also be implemented at the reciever's end also.

f)

TCP stands for transmission control protocol. This protocol is used for sharing the information between the sender and the user by setting up a reliable connection between the send and the reciever and once a stable connection is ensured between the two nodes it tends to share the packets or the data between the two nodes.A secure connection is confirmed using the Hand shaking methodology which works on the basis of acknowledging the packets that are recieved by the node. This can be imagined in this way. Suppose a person A makes a phone call to person B. Before continuing with the conversation person A send a hello over the phone call which further acknowledged by the person B by replying with hello to the person A. This methodolgy ensures that they both are connected now and are able to listen to each other. Hence they can further continue with their conversation

UDP:

It stands for user datagram protocol. Here the data is sent in the form of blocks of data known as Datagrams which are independent to each other. The data to be sent is converted into the form of datagrams and is exchanged between the two systems. As the datagrams are independent of each other, this doesn't ensures us that the data will be delivered to the reciever. This protocol is an unreliable form of protocol for exchanging the data between the two nodes.

f)

IP address: This is the logical address that is provided by the network to a node when the node is connected to the network. No two nodes can have the same ip address in a single network. When start comparing it with the given example it can be thought of as the unique id that is given to the account by the post office who is sending the merchandise.

MAC address: It is the hardware address of the system from where we are sending the packet in the network or where we have to send the packet. The work of the IP address is to fetch the MAC address of the system in a network using the address resolution protocol. MAC address is the actual address of the place to where the merchandise is to be sent.

PORT: It a unique number given to the process running on the remote system. It can be thought of as the name of the person to whom we have addressed the merchandise, i.e.; the person for whom the merchandise is sent.

Socket: It is combination of ip address and the port number. This finally helps us to identify that to where we have to send the merchandise and who is going to accept the merchandise at that particular location.

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