Basic Networking | Computer Networks - Computer Science Engineering (CSE) PDF Download

Basic Networking
The network layer is concerned with getting packets from the source all the way to the destination. The packets may require to make many hops at the intermediate routers while reaching the destination. This is the lowest layer that deals with end to end transmission. In order to achieve its goals, the network layer must know about the topology of the communication network. It must also take care to choose routes to avoid overloading of some of the communication lines while leaving others idle. The network layer-transport layer interface frequently is the interface between the carrier and the customer, that is the boundary of the subnet. The functions of this layer include :

  • Routing - The process of transferring packets received from the Data Link Layer of the source network to the Data Link Layer of the correct destination network is called routing. Involves decision making at each intermediate node on where to send the packet next so that it eventually reaches its destination. The node which makes this choice is called a router. For routing we require some mode of addressing which is recognized by the Network Layer. This addressing is different from the MAC layer addressing.
  • Inter-networking - The network layer is the same across all physical networks (such as Token-Ring and Ethernet). Thus, if two physically different networks have to communicate, the packets that arrive at the Data Link Layer of the node which connects these two physically different networks, would be stripped of their headers and passed to the Network Layer. The network layer would then pass this data to the Data Link Layer of the other physical network.
  • Congestion Control - If the incoming rate of the packets arriving at any router is more than the outgoing rate, then congestion is said to occur. Congestion may be caused by many factors. If suddenly, packets begin arriving on many input lines and all need the same output line, then a queue will build up. If there is insufficient memory to hold all of them, packets will be lost. But even if routers have an infinite amount of memory, congestion gets worse, because by the time packets reach to the front of the queue,

they have already timed out (repeatedly), and duplicates have been sent. All these packets are dutifully forwarded to the next router, increasing the load all the way to the destination. Another reason for congestion are slow processors. If the router's CPUs are slow at performing the bookkeeping tasks required of them, queues can build up, even though there is excess line capacity. Similarly, low-bandwidth lines can also cause congestion.We will now look at these function one by one.

Addressing Scheme
IP addresses are of 4 bytes and consist of :
i) The network address, followed by
ii) The host address

The first part identifies a network on which the host resides and the second part identifies the particular host on the given network. Some nodes which have more than one interface to a network must be assigned separate internet addresses for each interface. This multi-layer addressing makes it easier to find and deliver data to the destination. A fixed size for each of these would lead to wastage or under-usage that is either there will be too many network addresses and few hosts in each (which causes problems for routers who route based on the network address) or there will be very few network addresses and lots of hosts (which will be a waste for small network requirements). Thus, we do away with any notion of fixed sizes for the network and host addresses.

We classify networks as follows:

1. Large Networks: 8-bit network address and 24-bit host address. There are approximately 16 million hosts per network and a maximum of 126 ( 2^7 - 2 ) Class A networks can be defined. The calculation requires that 2 be subtracted because 0.0.0.0 is reserved for use as the default route and 127.0.0.0 be reserved for the loop back function. Moreover each Class A network can support a maximum of 16,777,214 (2^24 - 2) hosts per network. The host calculation requires that 2 be subtracted because all 0's are reserved to identify the network itself and all 1s are reserved for broadcast addresses. The reserved numbers may not be assigned to individual hosts.

2. Medium Networks: 16-bit network address and 16-bit host address. There are approximately 65000 hosts per network and a maximum of 16,384 (2^14) Class B networks can be defined with up to (2^16-2) hosts per network.

3.Small Networks: 24-bit network address and 8-bit host address. There are approximately 250 hosts per network.You might think that Large and Medium networks are sort of a waste as few corporations or organizations are large enough to have 65000 different hosts. (By the way, there are very few corporations in the world with even close to 65000 employees, and even in these corporations it is highly unlikely that each employee has his/her own computer connected to the network.) Well, if you think so, you're right. This decision seems to have been a mistake.

Address Classes
The IP specifications divide addresses into the following classes :

Basic Networking | Computer Networks - Computer Science Engineering (CSE)

Basic Networking | Computer Networks - Computer Science Engineering (CSE)

The document Basic Networking | Computer Networks - Computer Science Engineering (CSE) is a part of the Computer Science Engineering (CSE) Course Computer Networks.
All you need of Computer Science Engineering (CSE) at this link: Computer Science Engineering (CSE)
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FAQs on Basic Networking - Computer Networks - Computer Science Engineering (CSE)

1. What is computer science engineering (CSE) and how does it relate to basic networking?
Ans. Computer science engineering (CSE) is a field of study that combines computer science and engineering principles to design, develop, and manage software and hardware systems. Basic networking is an essential component of CSE as it involves the understanding and implementation of network protocols, network architectures, and communication techniques to ensure effective data transmission and connectivity between devices.
2. What are the key concepts in basic networking that a computer science engineering student should know?
Ans. Computer science engineering students should have a good understanding of key networking concepts such as IP addressing, subnetting, routing protocols, network topologies, network security, and the OSI model. These concepts form the foundation for designing and troubleshooting network infrastructures.
3. How does network latency affect network performance in computer science engineering?
Ans. Network latency refers to the delay in data transmission between two devices over a network. In computer science engineering, network latency can impact network performance by causing delays in data transfer, slow response times, and reduced overall efficiency. Minimizing network latency is crucial for optimizing network performance and ensuring smooth communication between devices.
4. What are the common network troubleshooting techniques used in computer science engineering?
Ans. Computer science engineering professionals often use various troubleshooting techniques to identify and resolve network issues. Some common techniques include analyzing network traffic using packet sniffers, verifying connectivity using ping and traceroute commands, checking network configurations, rebooting network equipment, and using network diagnostic tools to identify and fix problems.
5. How does network security play a role in computer science engineering and basic networking?
Ans. Network security is a critical aspect of computer science engineering and basic networking. It involves implementing measures to protect network resources, data, and devices from unauthorized access, attacks, and other security threats. Computer science engineering professionals need to have a strong understanding of network security principles, encryption techniques, firewalls, intrusion detection systems, and other security mechanisms to design and maintain secure network infrastructures.
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