CU-MCA-SEM-I-Advanced Computer Networks-Second Draft

Figure 2.2 Subnet masks There are two types of subnet masks: The number of bits allocated by the address class is the default Subnet Mask. In the relative class, this initial mask will allow a single network subnet. An administrator can create a Custom Subnet Mask to suit several Networks. How to Use a Subnet Mask? The router hides the network address behind the subnet mask. It displays the bits that are used to define the subnet. Each connection does have its own unique Ip address, such as 172.20.0.0 for the class B network, which contains all zero in the host component of the address. 11000001 is an example of an IP address. The first and second bits are 1 and the third bit is 0; thus, it is classified as class C. Figure 2.3 Subnet class The example above demonstrates how IP addresses must be reconstructed, making it easy for Internet routers to select the required networks to route data into. But, in a Class A network, 51 CU IDOL SELF LEARNING MATERIAL (SLM)

there may be millions of linked devices, and the router may take some time to locate the correct item. Methods of Subnet Masking The masking procedure can be submitted in two different ways: straight or short-cut. Straight For both address and the mask, you should use binary notation, and then use the AND function to retrieve the block address. Short-Cut Technique If the mask byte is 255, you must copy the byte from the destination address. Whenever the byte with in mask is 0, the byte in the location must be replaced with 0. You must put the masks and the address in byte and apply the AND operation whenever the byte in the masking would be neither 255 nor 0. If the retrieved network address meets the local network ID and the destination is on the same network as the source. If they don't match, the communication will have to be sent outside the local area network. Table 2.1 Subnet Masks Class Default subnet mask No. Of networks No. Of host per network A 255.0.0.0 256 16,777,214 B 255.255.0.0 65,536 65,534 C 255.255.255.0 16,77,216 126 2.3 CLASSLESS INTER-DOMAIN ROUTING (CIDR) The successor to class-oriented sub domains for Internet routing, Classless Inter-Domain Routing (CIDR), leads to better allocation of Internet addresses. It combines many Classes C Internet Protocol (IP) addresses to lighten the load on the Internet's routing tables. CIDR (Classless Inter-Domain Routing) is a technique of allocating Internet Protocol (IP) addresses that improved the quality of address distribution and substitutes the traditional version based on Class A, Class B, and Class C networks. It is also known as super netting. The initial purpose of CIDR was to reduce the rapid expiration of IPv4 addresses by inhibiting the development of network traffic on routers across the internet. As a response, the number of internet addresses available has skyrocketed. The internet's original elegant network design featured inefficiencies that quickly depleted the supply of unassigned IPv4 addresses. The elegant design featured the following elements: 52 CU IDOL SELF LEARNING MATERIAL (SLM)

With nearly 16 million IDs, Class A is the most common. Class B has 65,535 identities, while Class C has 254 identities. If a company requires and over 254 host machines, it will be moved to Class B. However, if the firm doesn't require them, this might waste over 60,000 hosts, reducing the availability of IPv4 addresses unnecessarily. An Internet Engineering Task Force (IETF) created CIDR in 1993 to address this issue. CIDR is built on varying subnet masking (VLSM) that allows network engineers to partition an IP address space into a network of subnets of varying sizes, allowing subnetworks with varying host counts to be created without wasting significant numbers of addresses. 2.4 ADDRESS RESOLUTION PROTOCOL (ARP) The Address Resolution Protocol (ARP) is a protocol for determining the data-link layer address (also known as the Media Access Control (MAC) address) linked with an Internet layer address (Layer 3 address like IPv4 address). RFC 826, which was published in 1982, defines ARP. ARP is a request-response or requisition protocol in which one device sends a request for information to another device, and the other device responds with the information requested. It's a pattern of message exchange. The link layer encapsulates ARP packets, which are exclusively distributed inside a single network. As a result, ARP is sometimes referred to as a link layer protocol. What is the purpose of ARP? Link layer addresses are used to interact with the user in a Local Area Network (LAN). Switches aren't set up for a standard that allows IP-based destination decisions inside the same network segment. An IP address is not assigned to a machine that is not connected. In that instance, the network will have to communicate using MAC addresses. A device has to understand the MAC address of another device's network interface in order to connect with it on the same LAN. This makes it possible for unicast contact between the various end devices. What is ARP and how does it work? An ARP table is present on every device that can handle IPv4 packets. Network interface to MAC address mappings is stored in an ARP table. Because switches aren't designed to handle IP packets, they don't have an ARP table. Switches, on the other hand, keep a cache that maps the MAC addresses of non-switch connected devices to this LAN to the port to which packets should be routed to reach that device. If the switch does not have destination MAC address in its cache, it will send the packet out on all open ports. When device 1 with IP 192.168.10.154 wishes to transmit a message to device 3 with IP 192.168.10.160, it looks up device 3's MAC address in its ARP cache. If the IP to MAC 53 CU IDOL SELF LEARNING MATERIAL (SLM)

conversion for device 3 does not present in the ARP cache, device 1 uses the ARP signals to communicate a data packet to the network, asking \"who possesses 192.168.10.160?\" The ARP broadcast packet is received by all devices in that network. An ARP response containing the MAC address of a device with the desired IP address will be returned. It's worth noting that the ARP answer is unicast, meaning it's only sent to the device that made the ARP request. When device 1 receives the ARP response, it adds an entry for device 3 to its ARP table. The switch's ARP cache is also updated to reflect which of its ports is linked to device 3. Figure 2.4 MAC Address 2.5 REVERSE ADDRESS RESOLUTION PROTOCOL (RARP): Reverse Address Resolution Protocol (RARP) is an acronym for Reverse Address Resolution Protocol, which is a computer networking protocol that allows a client computer to obtain its IP address from either a gateway server's Address Resolution Protocol tables or cache. In 54 CU IDOL SELF LEARNING MATERIAL (SLM)

gateway-router, the network administrator develops a database that maps the MAC address to the associated IP address. This protocol is being used to transfer data between two server sites. The client does not need to know who the server is capable of providing its request in advance. An administrator must configure each server's Medium Access Control (MAC) addresses individually. RARP is only capable of providing IP addresses. When a replacement computer is put up, it may or may not have a connected disc that can keep the IP Address permanently, so the RARP client application must request the IP Address from the router's RARP server. Under the assumption that an entry has been created in the router table, the RARP server will send the Domain name to the machine. Figure 2.5 RARP RARP's Origins: The university Network group suggested RARP in 1984. This protocol gave the workstation an IP address. These diskless workstations also served as the foundation for Sun Microsystems' principal workstations. RARP's Operation: The RARP is a Network Access Layer protocol that allows data to be sent between two sites in a network. Each network member has two distinct addresses: an IP (logical) address and a MAC (physical) address (the physical address). Software assigns the IP address, and the MAC address is built into the hardware after that. 55 CU IDOL SELF LEARNING MATERIAL (SLM)

Any ordinary machine on the network can act as a RARP server and reply to RARP queries. It must, however, store the information for all MAC addresses as well as their IP addresses. Just these RARP servers can respond to a RARP request if it is accepted by the network. The data packet must be transmitted through very low-cost network tiers. This means the package is sent to each participant at the same time. With such an Ethernet routing protocol and its own physical address, the client sends a RARP request. The client receives its IP address from the server. 2.6 DYNAMIC HOST CONFIGURATION PROTOCOL DHCP The Dynamic Host Configuration Protocol (DHCP) is a client/server method that assigns an IP address and other configuration information to an Internet Protocol (IP) host, such as the subnet mask and default gateway, automatically. DHCP is defined in RFCs 2131 and 2132 as an Internet Engineering Task Force (IETF) rule based on the Bootstrap Protocol (BOOTP), which shares many implementation specifics with DHCP. DHCP is a protocol that allows hosts to get TCP/IP configuration settings from a DHCP server. DHCP Server is an optional networking server role in Windows Server 2016 that you can install on your networks to lease IP addresses as well as other information to DHCP clients. The DHCP client is included as part of TCP/IP in all Windows-based client web browsers, and it is activated by default. Why should you utilise DHCP? To access the service and its resources, every machine on a TCP/IP-based network needs a unique unicast IP address. IP addresses for windows laptops or computers relocated from one subnet to the other must be manually set without DHCP, and IP addresses for machines withdrawn first from network should be manually recovered. This entire procedure is automated and handled centrally with DHCP. When a DHCP- enabled client connects to the network, the DHCP server keeps a pool of IP addresses and rents one to it. Because the Domain names are dynamic (leased) instead of static (permanently issued), they are immediately returned to the pools for reallocation when they are no longer in use. The network administrator configures DHCP servers to store TCP/IP configuration information and give address configuration to DHCP-enabled customers in the form of a lease offer to DHCP-enabled clients. The configuration information is stored in a database by the DHCP server, which includes: All clients on the network should have valid TCP/IP configuration parameters. Valid IP addresses, as well as prohibited ones, are kept in a pool for client assignment. IP addresses that are reserved for specific DHCP clients. This allows a single IP address to be assigned to 56 CU IDOL SELF LEARNING MATERIAL (SLM)

a single DHCP client in a consistent manner. The lease period, or the amount of time the IP address could be used before it needs to be renewed. When a DHCP-enabled client accepts a lease offer, it receives the following: It must have a valid IP address for both the subnet it is connecting to.Additional parameters that a DHCP server is designed to provide to clients are known as requested DHCP options. Router (default gateway), DNS Servers, and DNS Domain Name are examples of DHCP choices. DHCP's Advantages The following are some of the advantages of DHCP.  Configuration of a dependable IP address. Manual IP address configuration issues, such as typographical errors or address conflicts caused by assigning an IP address to even more than one computer, are minimised by DHCP.  Network administration is simplified.  To make network administration easier, DHCP supports the following features:  TCP/IP setting that is centralised and automated.  TCP/IP setups can be defined from either a central location.  DHCP options allow you to specify a wide range of additional TCP/IP setup variables. The efficient management of IP address changes for users that must be updated on a regular basis, such as portable devices that roam across a wireless network. The use of a DHCP relay agent to forward initial DHCP messages, eliminating the requirement for a DHCP server on each subnet. 2.7IPV4 AND IPV6 What exactly is IPV4? IPv4 is a version of the Internet Protocol that is commonly used to designate devices on the network via an addressing system. In 1983, it was the first version of IP to be used in production on the ARPANET. It stores 2^32 addresses, and is more than 4 billion addresses, using a 32-bit address scheme. It is the most important Internet Protocol, carrying 94% of all Internet traffic. What exactly is IPv6? The Internet Protocol version 6 (IPv6) is the most recent version. This new IP address version is being implemented in order to meet the need for additional Internet addresses. It was 57 CU IDOL SELF LEARNING MATERIAL (SLM)

created with the goal of resolving IPv4 difficulties. It allows 340 undecillion distinct address space with 128-bit address space. IPv6 is also known as IPng (Internet Protocol next generation). It was started by the Internet Engineer Taskforce in early 1994. IPv6 is the name given to the design and development of such a suite. Difference between IPV4 and IPV6:  IPv4 uses a 32-bit address, while IPv6 uses a 128-bit address.  IPv4 uses a numeric addressing scheme, whereas IPv6 uses an alphanumeric scheme.  A dot (.) separates IPv4 binary bits, whereas a colon separates IPv6 binary bits (:).  There are 12 header fields in IPv4 and 8 header fields in IPv6.  IPv4 supports broadcast, however IPv6 does not.  Checksum fields are present in IPv4 but are absent in IPv6.  When comparing IPv4 and IPv6, we can see that IPv4 supports VLSM (Variable Length Subnet Mask), whereas IPv6 does not.  IPv4 maps to MAC address using ARP (Address Resolution Protocol), but IPv6 maps to MAC address using NDP (Neighbour Discovery Protocol). IPv4's Features IPv4 has the following characteristics: The Connectionless Protocol allows for the creation of a basic virtual communication layer that may be used by a variety of devices. It necessitates less memory and makes it easier to recall addresses. Millions of gadgets now support the protocol. Provides video libraries as well as conferences. Figure 2.6 IPv4 vs IPv6 58 IPv6's Features IPv6 has the following features:  Infrastructure for hierarchical addressing and routing CU IDOL SELF LEARNING MATERIAL (SLM)

 Configurations that are both stateful and stateless  Support for service quality (QoS)  An optimal approach for interacting with neighbours Difference IPv4 and IPv6 Addresses: IPv4 and IPv6 are both binary integers that represent IP addresses. In terms of IPv6 vs. IPv4, IPv4 is a 32-bit binary number, whereas IPv6 is a 128-bit binary number. Periods divide IPv4 addresses, while colons divide IPv6 addresses. Table 2.2 IPV4 vs IPV6 IPV4 IPv6 IPv4 has 32-bit address length IPv6 has 128-bit address length It Supports Manual and DHCP address It supports Auto and renumbering address configuration configuration In IPv4 end to end connection integrity In IPv6 end to end connection integrity is is Unachievable Achievable Address space of IPv6 is quite large it can It can generate 4.29×109 address space produce 3.4×1038 address space Security feature is dependent on IPSEC is inbuilt security feature in the IPv6 application protocol Address representation of IPv4 is in Address Representation of IPv6 is in decimal hexadecimal In IPv4 Packet flow identification is not available In IPv6 fragmentation performed only by sender 2.8SUMMARY  A network is a collection of two or more computing devices that are linked together. Typically, all network devices were connected to a central hub, such as a router. 59 CU IDOL SELF LEARNING MATERIAL (SLM)

 Subnetworks, or lesser subdivisions of a network, are also possible. Sub networking is a technique for managing thousands of IP addresses and associated devices on very large networks, such as those offered by ISPs.  The network layer is where everything really to do with inter-network connections happens.  Setting up data packet routes, checking to verify if a server on another network has up and running, or addressing & receiving IP packets from those other networks are all examples of this. Because the great bulk of Internet traffic is sent through IP, this last procedure is likely the most significant.  There is also no \"network\" layer in the TCP/IP model. The network layer of the OSI model generally correlates to the Internet layer of the TCP/IP paradigm. The network layer is layer 3 in the OSI model, while the Internet layer is layer 2 under the TCP/IP paradigm.  In these other words, both network layer and also the Internet layer are essentially the same thing, and they are based on distinct Internet models. 2.9 KEYWORD • ARP-The Address Resolution Protocol is in charge of keeping track of how IP addresses are translated into physical addresses. • TCP-The Transmission Control Protocol (TCP) is a connection-oriented protocol which decomposes data into small chunks, routes it to its destination, and then reassembles it. • Connection-oriented Communication-Between two machines, direct contact is established. Consider talking on the phone with a friend. 2.10 LEARNING ACTIVITY 1. If you are a network administrator, how will you configure IPV6 Routing? ___________________________________________________________________________ _____________________________________________________________________ 2. Your router has the following IP address on Ethernet0: 172.16.2.1/23. Which of the following can be valid host IDs on the LAN interface attached to the router? 1. 172.16.1.100 2. 172.16.1.198 3. 172.16.2.255 60 CU IDOL SELF LEARNING MATERIAL (SLM)

4. 172.16.3.0 ___________________________________________________________________________ _____________________________________________________________________ 2.11UNIT END QUESTIONS A. Descriptive Questions Short Questions 1. What are the two elements of an IP address? 2. What is classful addressing? 3. What is subnet mask? 4. What do you mean by classless Inter-domain routing? 5. Write about DHCP. Long Questions 1. How does IP works? 2. Explain about subnetting. 3. Discuss the methods of subnet mask. 4. Explain about ARP and RARP. 5. Compare IPV4 and IPV6 B. Multiple Choice Questions 1. _____is a unique label given to devices linked to a computer network that communicates using the IP protocol a. Communication Protocol b. Internet Protocol c. Source d. Destination 2. ____ component identifies the network’s individual computers 61 a. Suffix b. Prefix c. Internet d. protocol CU IDOL SELF LEARNING MATERIAL (SLM)

3. IP was created to function in a _____ network a. Datagram b. closed c. open d. dynamic 4. A _____ distinguishes between the IP addresses and the host address in an IP address. a. Packet b. Subnet mask c. Destination d. Source 5. ____ is a technique to allocate IP addresses that improved the quality of address distribution. a. CIDR b. ARP c. RARP d. DHCP Answers 1-b,2-a, 3-d, 4- b, 5-a 2.12 REFERENCES Reference books • Behrouz A Forouzan, “Data Communications and Networking”, McGraw Hill. • Andrew S. Tanenbaum, “Computer Networks”, Pearson Education. • Subir Kumar Sarkar, T.G. Basavaraju, C. Puttaamadappa, “AdHoc Mobile Wireless Network: Principles, Protocols, and Applications, CRC Press. Textbook references • James F. Kurose, Keith W. Ross, “Computer Networking”, Pearson Education. 62 CU IDOL SELF LEARNING MATERIAL (SLM)

• Michael A. Gallo, William M. Hancock, “Computer Communications and Networking Technologies”, CENGAGE Learning Websites: • https://www.techopedia.com/definition/10062/wireless-communications • https://www.computernetworkingnotes.com/ • https://www.guru99.com 63 CU IDOL SELF LEARNING MATERIAL (SLM)

UNIT 3-THE ROUTING PROTOCOLS 64 STRUCTURE 3.0 Learning Objectives 3.1 Introduction to Routing protocols 3.2 Types of Routing protocols 3.2.1 Static Routing Protocols 3.2.2. Dynamic Routing Protocols 3.3 Distance Vector Routing Protocol (DVR) 3.4 Routing Information Protocol (RIP) 3.5 Interior Gateway Protocol (IGP) 3.6 Link State Routing Protocols 3.7 Protocol tables for routing 3.8 Exterior Gateway Protocol (EGP) 3.9 Open Shortest Path First (OSPF) 3.10 Border Gateway Protocol (BGP) 3.11 IP Multicasting 3.12 Address Assignments 3.13 Session Discovery 3.14 Summary 3.15 Keywords 3.16 Learning Activity 3.17 Unit End Questions 3.18 References 3.0 LEARNING OBJECTIVES After studying this unit, you will be able to: • State the basics of Routing protocols • Explain the advantages and disadvantages of protocols • List the concepts of Multi cast routing protocols CU IDOL SELF LEARNING MATERIAL (SLM)

• Outline the working address assignments • Describe the concept of Session discovery 3.1 INTRODUCTION TO ROUTING PROTOCOLS Routing Protocols are a collection of rules that routers employ to connect between source and destination. They do not transfer data from a source to a destination; instead, they change the routing table which holds the data. Network Router protocols describe how routers communicate with one another. It enables the network to choose routes between these two computer network nodes. 3.2 TYPES OF ROUTING PROTOCOLS There are mainly two types of Network Routing Protocols  Static  Dynamic Figure 3.1 Types of Routing Protocol 3.2.1 Static Routing Protocols When an administrator manually allocates the route from the source to the destination, static routing protocols are employed. It improves the network's security. Advantages  There is no load on the router's CPU.  Between links, there is no unused bandwidth. 65 CU IDOL SELF LEARNING MATERIAL (SLM)

 Routes can only be added by the administrator. Disadvantages  Each router's connection must be known by the administrator.  Because it is time consuming, it is not a good choice for large networks.  When a connection fails, the entire network goes down, which is impractical in small networks. 3.2.2 Dynamic Routing Protocols Another important form of routing protocol is dynamic routing protocols. It enables routers to automatically add information from connected routers to their routing tables. When the topological structure of the network changes, these protocols send out topology updates. Advantage  Even on larger networks, it's easier to configure.  It will be able to choose an alternate route dynamically if a link fails.  It assists you in load balancing over many links. Disadvantage  Because updates are exchanged between routers, bandwidth is used.  Routing protocols increase the load on the router's CPU or RAM. 3.3 DISTANCE VECTOR ROUTING PROTOCOL (DVR) Distance Vector Protocols use a lot of bandwidth and slow converge to announce its routing table to every strongly linked neighbour at specific time intervals. When a route becomes unavailable in the Distance Vector routing protocol, all routing databases must be updated with new information. These protocols choose the best way to a destination node in a specific direction based on hop counts. A distance vector routing protocol, such as RIP, is an example of a dynamic protocol. The hop count is the number of routers between the origin and destination networks. The pathway with the fewest hops will be selected as the best. Advantages:  Network updates are exchanged on a regular basis, but it is always broadcast.  The routing information obtained from neighbouring routers is always trusted by this protocol.  Routing information (updates) are always broadcast. 66 CU IDOL SELF LEARNING MATERIAL (SLM)

 In updates, full routing databases are sent.  Routing information obtained from neighbouring routers is always trusted by routers. This is often referred to as rumour routing. Disadvantages:  Unnecessary signal is routed as routing information is transmitted on a regular basis, consuming available bandwidth.  Routing Protocols on the Internet  Because full routing tables are shared, security risks arise. The entire topology will be very simple to identify if an authorised individual accesses the network.  In addition, publishing network traffic on a regular basis generates needless bandwidth. 3.4 ROUTING INFORMATION PROTOCOL (RIP) For both LAN and WAN networks, RIP is used. Also, it runs on the OSI model's Application layer. The Routing Information Protocol is the full name of this protocol. There are two variations of RIP. RIPv1 Vs RIPv2 The initial version, also known as RIPv1, aids in the determination of network pathways based on IP destination and hop count travel. RIPv1 also communicates with the network by publishing its IP table to any and all network routers. Because it delivers its routing table to a multicast address, RIPv2 is a little more advanced. 3.5 INTERIOR GATEWAY PROTOCOL (IGP) IGRP is a CISCO-developed subclass of the distance-vector internal gateway protocol. It was created to get around the RIP limits. Load, bandwidth, latency, MTU, and dependability are the metrics employed. It's a common way for routers to share routing information inside an autonomous system. Because it broadcasts every 90 seconds and has a maximum hop count of 255, this form of routing protocol is appropriate for bigger networks. In comparison to RIP, it allows you to maintain larger networks. IGRP is also frequently used because it avoids routing loops by automatically updating this when route changes take place within a network. It also has the option of balancing traffic across equal and unequal metric damage. 3.6 LINK STATE ROUTING PROTOCOLS 67 CU IDOL SELF LEARNING MATERIAL (SLM)

When it comes to finding the ideal routing path, Link State Protocols use a unique approach. The route is generated in this protocol due to the speed of the shortest path as well as the cost of materials. These protocols have a better understanding of the Internet than every distance vector routing protocol. SPF (Shortest Path First) protocol is another name for this. The Open Shortest Path First (OSPF) protocol is an example of a link state routing protocol. Features Hello messages, also called as keep-alive messages, are used to locate and reconnect with neighbours. The idea of triggered updates is employed, which means that updates are only triggered when the topology changes. Only the number of updates requested by the neighbouring router is exchanged. Three tables are maintained by the link state routing protocol:  The neighbour table is a table that exclusively includes information about the router's neighbours, i.e., to whom an adjacency has now been formed.  This page includes information about the entire topology, including both the fastest and backup routes to a specific advertised network.  The optimal paths to the offered network are listed in the routing table. Advantages  Because it keeps separate databases for the optimal and backup routes (the entire topology), it has a better understanding of the entire network than just about any distance vector routing technology.  As a result of the application of the concept of triggered updates, there is no more wasteful bandwidth usage as seen in the distance vector routing protocol.  When there is a topology change, partial updates are triggered rather than a full update like the distance vector routing protocol, which exchanges the entire routing database. 3.7 PROTOCOL TABLES FOR ROUTING: The following three tables are maintained by the link state routing protocol: Neighbour table: This table solely provides information about the router's neighbours. Adjacency, for example, has developed. Topology table: This table keeps track of the entire topology. It contains, for example, both the fastest and backup pathways to a specific advertising network. 68 CU IDOL SELF LEARNING MATERIAL (SLM)

The optimal routes to the advertised networks are all stored in a routing table. Benefits: Because this protocol has distinct databases for the optimal and backup routes, it has a better understanding of the inter-network than just about any other route discovery routing technology. The concept of prompted updates is used; therefore there is no waste of bandwidth. If there is a topology update, partial changes will be triggered, thus the entire routing table will not need to be updated. 3.8 EXTERIOR GATEWAY PROTOCOL (EGP) EGP is a protocol for exchanging data between gateway hosts in autonomous systems that are neighbours. This routing protocol provides a platform for devices to share data between domains. EGP stands for Exterior Gateway Protocol in its entire form. Existing routers, network resources, route charges, and surrounding devices are all part of the EGP protocol. Enhanced Interior Gateway Routing Protocol (EIGRP) is a protocol that allows you to route (EIGRP) EIGRP is a hybrid routing protocol which combines routing protocols, distance vector routing protocols, and link-state routing protocols into one package. Enhanced Interior Gateway Routing Protocol is the complete form of the routing protocol EIGRP. It would use the same composite metrics like IGRP to route the same protocols, allowing the network to choose the optimum path destination. 3.9OPEN SHORTEST PATH FIRST (OSPF) The Open Shortest Path First (OSPF) protocol is indeed a link-state IGP designed specifically for IP networks that use the Shortest Path First (SPF) form of routing. OSPF routing enables you to keep databases that include information about the network's topology. When the topology of the network changes, it employs the Dijkstra’s algorithm (Shortest path algorithm) to rebuild network paths. This protocol too is highly secure, because it can validate protocol modifications in order to keep data safe. The following are some key distinctions between the Distance Vector and Link State routing protocols: Table 3.1 Distance Vector vs Link State Distance Vector Link State The whole routing table is sent via the Distance Only link-state information is sent using the Vector protocol. Link State protocol. 69 CU IDOL SELF LEARNING MATERIAL (SLM)

Distance Vector Link State Loops in the routing are a risk. It's less likely to become stuck in a loop. Updates are occasionally sent via broadcast. For routing updates, only the multicast approach is used. It is straightforward to set up. This routing technique is difficult to set up. Does not know network topology. Know the entire topology. Example RIP, IGRP. Examples: OSPF IS-IS. 3.10BORDER GATEWAY PROTOCOL (BGP) BGP is the Internet's final routing protocol, and it is categorized as a DPVP (distance path vector protocol). BGP stands for Border Gateway Protocol in its entire form. When updates are made to the router table, this routing protocol provides updated data. As a result, topology changes are not automatically discovered, requiring the user to manually configure BGP. Border Gateway Protocol (BGP) is a protocol that is used to exchange internet routing information between ISPs with different protocols. The protocol can link any autonomous system's internetwork together utilising any topology. The only stipulation here is that every AS have at least one BGP-capable router that is connected to a minimum one other AS's BGP router. The primary purpose of BGP is to communicate network reachability information with the other BGP systems. Based on the information transmitted between BGP routers, the Border Gateway Protocol creates an autonomous systems graph. Border Gateway Protocol (BGP) Characteristics: Configuration of Inter-Autonomous Systems: BGP's primary function and to provide interactions between different autonomous systems. Next-Hop Paradigm is supported by BGP. Within the AS, coordination among several BGP speakers (Autonomous System). Path Information: In addition to the accessible destination so next destination pair, BGP advertisements offer path information. 70 CU IDOL SELF LEARNING MATERIAL (SLM)

Policy Support: BGP can take actions that the administrator can configure. A router running BGP, for example, can be set to discriminate between routes known within the AS and routes recognized from outside the AS.  TCP (Transmission Control Protocol) is used.  BGP is a protocol that helps networks save bandwidth.  CIDR is supported by BGP.  Security is also supported by BGP. Border Gateway Protocol (BGP) Functionality:  BGP peers fulfil three roles, which are listed below.  The first peer recruitment and authentication are the first two functions. Both peers establish a TCP connection and exchange messages to ensure that both parties have agreed to interact.  The second function primarily focuses on sending reachability information, both negative and positive.  The third function ensures that the neighbours and their network connections are working properly. Functions of BGP Route Information Management: Route Storage: Each BGP keeps track of how to connect to other networks. Special strategies are utilised in this assignment to identify when and how to use the information obtained from peers to correctly update the routes. Route Selection: Each BGP selects good routes to every network on the internet network based on the information inside its route databases. Route advertisement: Every BGP speaker informs its peer about what it knows about different networks and how to access them on a regular basis. What are Routing Protocols used for? The following reasons need the use of routing protocols:  Allows for the most optimal path selection.  Allows for loop-free routing.  Convergence occurs quickly.  Minimizes update traffic and is simple to set up.  Adapts to new situations 71 CU IDOL SELF LEARNING MATERIAL (SLM)

 Scales up to a colossal size  Hosts and routers that are already in use are compatible.  Variable length is supported. 3.11IP MULTICASTING IP multicasting is a communication method in which data is sent from a server to a group of clients who have expressed an interest in receiving it. Any client can join or leave the conversation at any time. Though the overall notion appears to be straightforward, the manner in which it is performed necessitates a thorough comprehension. So, in this tutorial, we'll go over the fundamentals of IP multicasting and how it works. Figure 3.2 IP Multicasting IP address for multicast To comprehend how multicasting works, one must first comprehend the multicast IP address structure. Multicast communication is based on multicast IP addresses. In terms of IP addresses, multicast IP addresses are assigned to Class D IP addresses. The structure of Class D IP addresses is as follows: As a result, multicast IP addresses span from 224.0.0.0 to 239.255.255.255. There are some reserved multicast IP addresses or even well-known IP addresses, similar to the case of ports (where we can have well known ports such as 0-1024). 224.0.0.1, for example, denotes every system on a subnet. Every router on a subnet is represented by 224.0.0.2, and so on. When using make the public aware, the server delivers data to a specific multicast IP address, and clients who want to receive it must listen to the same multicast address. These customers can be from a variety of networks. A host group is a collection of clients listening to the same multicast address. On a single network, multicasting is possible. The idea of multitasking operates as follows on a single network: 72 CU IDOL SELF LEARNING MATERIAL (SLM)

The server sends data packets to a multicast IP address or a particular destination IP address. The multicast IP address is translated to an ethernet address and delivered over the network using the mapping mentioned above. When interacting with the systems IP layer, a process on a client that wants to receive multicast traffic must provide the same multicast IP address, which further configures lower levels to seek for such multicast packets. Because 32 multicast group IDs can correlate to one ethernet address, when a multicast packet is generated on the system, it is screened to eliminate unnecessary packets (explained above) Please keep in mind that on a single client, numerous processes may seek to delivery date with the same multicast ID. The kernel ensures that each process receives a duplicate of the packet in this situation. Using multiple networks for multicasting When multicast Data packet have to go across networks, things get a little more complicated because many routers are involved. Each router in the path should be able to enable multicasting and have multicast packet forwarding entries. When a client enters a multicast group, a distribution tree is generated for it that specifies the multicast traffic path for this multicast connection. When it comes to routers, it's a good idea to familiarise yourself with some route command samples. A distribution tree can contain many routers, and a single router can be found in numerous distribution trees. It implies that if a router belongs to X distribution trees, it must have X forwarding entries, each of which corresponds to a different distribution tree. Multicast Routing: Multicast routing is a subset of broadcast routing, with unique characteristics and challenges. Packets are being sent to all nodes via broadcast routing, even if nodes do not want them. However, in Multicast routing, data is only sent to nodes that desire to receive packets. 73 CU IDOL SELF LEARNING MATERIAL (SLM)

Figure 3.3 Packet Routing Only once the router has determined that there are nodes that want to accept multicast packets (or streams), should it forward them. To avoid looping, multicast routing uses the spanning tree protocol. To detect and eliminate duplicates and loops, multicast routing employs the reverse path forwarding approach. A router's primary function is to route packets. In other words, when it gets an IP packet, it must examine the destination address, consult the routing table, and determine the next hop to which the IP packet should be sent. Routing protocols are used to discover new networks and populate the routing table. 3.12 ADDRESS ASSIGNMENTS: Devices can be connected to hosts both dynamically as they enter the network or permanently through hardware or software configuration. To use a static IP address is another term for persistent configuration. Using a dynamic IP address, on the other hand, is when a laptop's IP address is given each time it restarts. The Dynamic Host Configuration Protocol is used by the network to assign dynamic IP addresses (DHCP). The most often used mechanism for assigning addresses is DHCP. It eliminates the administrative overhead of giving each device on a network a unique static address. It also permits devices to share a network's limited address space if only a few of them are online at the same time. In most recent desktop operating systems, dynamic IP setup is enabled by default. The address issued by DHCP is usually tied to a lease and has an expiration date. The address may be allocated to another device if the license is not renewed either by host before it 74 CU IDOL SELF LEARNING MATERIAL (SLM)

expires. Some DHCP clearly and frequently to transfer the same IP address to a server each time it enters the network, depending on its MAC address. A network administrator can use DHCP to assign specific IP addresses to devices based on their MAC addresses. DHCP isn't the only method for dynamically assigning IP addresses. The Bootstrap Protocol is a forerunner of DHCP and is comparable to it. The Point-to-Point Protocol's dynamic address characteristics are used in dialup as well as some broadband networks. Static addressing is most commonly used on network infrastructure computers and equipment, like routers and mail servers. An operating system may provide a link-local address to a host via stateless address autoconfiguration in the lack or failure of static and dynamic address setups. 3.13SESSION DISCOVERY: The technique of automatically finding products and equipment on a network is known as service discovery. The Service Discovery Protocol (SDP) is a network technology that identifies resources in order to detect networks. Service discovery has traditionally aided users in reducing configuration requirements by presenting them with additional information, such as a Bluetooth-enabled printers or server. The notion has lately been expanded to network or scattered container resources as \"services\" that may be discovered and accessed. What is Service Discovery, and how does it work? Service Discovery has the capacity to instantly locate a network, eliminating the need for a lengthy configuration setup process. Devices communicate across the network using a standard language, letting devices or services to connect without the need for manual intervention. (For example, AWS service discovery, Kubernetes service discovery) What is the Process of Service Discovery? The service provider, the service consumer, and the service registry are the three components of Service Discovery. 1) When a Service Provider first enters the system, it registers with the service registry and then de-registers when it leaves. 2) The Service Consumer obtains a provider's location from the service registry and links it to the provider. 3) The Service Registry is a database which keeps track of where service instances are on the network. Clients can browse network locations received from the service registry if the service registry is highly accessible and up to date. A service registry is a collection of servers that maintain consistency through the use of a replication protocol. 75 CU IDOL SELF LEARNING MATERIAL (SLM)

What are the Benefits of Service Discovery (Both Server and Client Side)? The benefit of server-side web services is that it renders the client application lighter by eliminating the searching method and instead sending a request for services towards the router. The benefit of client-side service discovery is that it eliminates the need for the client application to go through a router or load balancer, saving time and money. Server-side and client-side service discovery are the two types of operating discovery. Client applications can use server-side service discovery to find services via a router or load balancer. Client-side service clients approach client applications to locate services by searching or querying a service registry, which contains both service instances and endpoints. 3.14SUMMARY  Routing protocols for the Internet Protocol (IP) have a single goal: to update the IP routing table with both the best routes available at the time. The goal is straightforward, but the procedure and solutions are not. Routing protocols specify how routers communicate with one another to identify the optimum paths to each destination.  Routers increased processing power & Random-Access Memory as networks became more complicated over time (RAM). As just a result, engineers devised new routing protocols that took use of faster networks and routers, thus altering routing methods.  Routing protocols make it easier for routers to learn routes by requiring each router to announce the routes it is aware of. Each router starts with only the routes that are immediately connected to it.  Then, each router transmits messages that list the routes, as described by the routing protocol. When a router receives a routing update message from some other router, it gains knowledge of the subnets & adds routes to its routing database. All routers in an internetwork can learn about certain subnets if they all participate.  A routing protocol is a set containing messages, rules, & algorithms used among routers for the goal of learning routes in general. This procedure entails exchanging and analysing route data. In a process called as path selection, each router selects the optimum route to every subnet and stores it in its IP routing database. RIP, EIGRP, OSPF, and BGP are examples of routing protocols. 3.15 KEYWORD  Service Provider-The service provider, the service consumer, and the service registry are the three components of Service Discovery. 76 CU IDOL SELF LEARNING MATERIAL (SLM)

 Multicast routing- Multicast routing is a subset of broadcast routing, with unique characteristics and challenges. Packets are being sent to all nodes via broadcast routing, even if nodes do not want them. However, in Multicast routing, data is only sent to nodes that desire to receive packets. 3.16 LEARNING ACTIVITY 1. A network administrator is connecting hosts A and B directly through their Ethernet interfaces, as shown in the illustration. Ping attempts between the hosts are unsuccessful. What can be done to provide connectivity between the hosts? 1. A crossover cable should be used in place of the straight-through cable. 2. A rollover cable should be used in place of the straight-through cable. 3. The subnet masks should be set to 255.255.255.192. 4. A default gateway needs to be set on each host. 5. The subnet masks should be set to 255.255.255.0. ___________________________________________________________________________ ___________________________________________________________________________ 2. Decide, what is the maximum number of IP addresses that can be assigned to hosts on a local subnet that uses the 255.255.255.224 subnet mask? ___________________________________________________________________________ ___________________________________________________________________________ 3.17UNIT END QUESTIONS A. Descriptive Questions Short Questions 1. What are the types of routing protocols? 2. What is a Dynamic routing protocol? 3. What is RIP? 77 CU IDOL SELF LEARNING MATERIAL (SLM)

4. What is neighbour table? 5. Write about BGP. Long Questions 1. Write the advantages and disadvantages of static routing protocols. 2. Explain about DVR. 3. Discuss the methods of subnet mask. 4. Explain about link state routing protocols. 5. Compare distance vector and link state. B. Multiple Choice Questions 1. _____ enables the network to choose routes between these two computer network nodes. a. Network router protocol b. Routing Protocol c. static routing d. link state routing 2. _____ is an example of dynamic protocol a. ARP b. RARP c. RIP d. DHCP 3. Which table provides information about the router's neighbours? a. Prompt b. Design c. Protocol d. Neighbour 4. ____ is a protocol for exchanging data between gateway hosts in autonomous systems. a. BIG b. EGP c. RIP d. DHCP 5. OSPF routing enables you to keep databases that include information about the ____ 78 CU IDOL SELF LEARNING MATERIAL (SLM)

a. network's topology b. Preference c. Distance vector d. entire topology Answers 1-a, 2-c, 3-d, 4- b, 5- a 3.18 REFERENCES Reference books • Behrouz A Forouzan, “Data Communications and Networking”, McGraw Hill. • Andrew S. Tanenbaum, “Computer Networks”, Pearson Education. • Subir Kumar Sarkar, T.G. Basavaraju, C. Puttaamadappa, “AdHoc Mobile Wireless Network: Principles, Protocols, and Applications, CRC Press. Textbook references • James F. Kurose, Keith W. Ross, “Computer Networking”, Pearson Education. • Michael A. Gallo, William M. Hancock, “Computer Communications and Networking Technologies”, CENGAGE Learning Websites: • https://www.techopedia.com/definition/10062/wireless-communications • https://www.computernetworkingnotes.com/ • https://www.guru99.com 79 CU IDOL SELF LEARNING MATERIAL (SLM)

UNIT 4-TRANSPORT LAYER STRUCTURE 4.0 Learning Objectives 4.1 Introduction to Transport Layer 4.2 Transport Layer Design Issues 4.3 Addressing 4.4 TCP Connection Establishment 4.5 Flow control in Transport Layer 4.6 Multiplexing and Demultiplexing in Transport Layer 4.7 Summary 4.8 Keywords 4.9 Learning activity 4.10 Unit End Questions 4.11 References 4.0 LEARNING OBJECTIVES After studying this unit, you will be able to: • Learn the basics of Routing protocols • Explain the design issues of transport layer • Describe the concepts of Transport layer • List the working address assignments • Outline the concepts of multiplexing and demultiplexing 4.1 INTRODUCTION TO TRANSPORT LAYER The transport layer is in charge of delivering the full message from process to process. A process is a computer programme that runs on a server. While the network layer is in charge of ensuring that individual packets are delivered from point A to point B, it is unaware of any relationships between those packets. It treats each one separately, as if each component belonged to a different message, which it does not. The transport layer, but at the other hand, oversees both error control and flow management at the source-to-destination level, ensuring that the entire message arrives intact and in sequence. 80 CU IDOL SELF LEARNING MATERIAL (SLM)

Figure 4.1 Transport Layer The transport layer also has the following responsibilities: • Addressing of service points several programmes are frequently run simultaneously on computers. As a result, source-to-destination delivery encompasses not just distribution from one computer to the next, but also delivery from one computer's specific process (running programme) to another's specific process (running programme). As a result, a form of address known as a service-point address must be included in the transport layer header (or port address). Each packet is delivered to the correct computer by the network layer, and the full message is sent to the right procedures on that computer by the transport layer. • Reassembly and segmentation A message is broken down into transmittable parts, each with its own sequence number. These numbers allow the transport layer to accurately reassemble the message once it arrives at its destination, as well as detect and replace packets lost during transmission. • Connection management. Connectionless or connection-oriented transport layers are both possible. A connectionless data packet interprets each segment as a separate packet and sends it to the destination machine's transport layer. Before delivering packets, a connection-oriented transport layer establishes a link with both the transport layer at the destination computer. The connection is terminated once all of the data has been transferred. • Controlling the flow of information. The transport layer, like the data connection layer, is in charge of flow control. Flow control at this layer, on the other hand, is done end to end instead of across a single link. • Error detection and correction. The transport layer, like the data connection layer, is in charge of error control. At this layer, however, error control is done process per process rather than over a single link. The sending transport layer ensures that the complete message is delivered without error to the receiving transport layer (damage, loss, or duplication). Retransmission is typically used to rectify errors. 81 CU IDOL SELF LEARNING MATERIAL (SLM)

4.2 TRANSPORT LAYER DESIGN ISSUES Accepting data from the session layer, segmenting it, and sending it all to the network layer. • Ensure that data is delivered correctly and efficiently. • Isolate the higher layers of the body from technological advancements. • Controlling errors and the flow of information. • The message is delivered via the transport layer from one process to another on two separate hosts. • As a result, it must conduct a variety of activities in order to assure the accuracy of the data. • transmission of the message The transport layer performs the following functions: • Connection Establishment, Maintenance, and Release • Addressing • Transfer of Information • Controlling the Flow • Controlling Errors • Controlling Congestion Creating, Maintaining, and Releasing the Connection: • On the request of upper levels, the transport layer initiates, maintains, and releases end-to-end transport connections. • Setting up a connection entails allocating buffers to store user data, synchronising packet sequence numbers, and so on. • At the request of the top layer, a connection is withdrawn. 4.3 ADDRESSING An addressing system is essential to attain the message through one process to another. • A system can have multiple processes running at the same time. • The transport module applies an addressing method called por number to predict the right process among the several executing processes. • A unique port number is assigned to each process. Data Transmission: 82 CU IDOL SELF LEARNING MATERIAL (SLM)

• The transport layer divides user data into smaller pieces and applies a transport layer header to every unit, establishing a transport protocol data unit (TPDU) (Transport Layer Data Unit). • The TPDU is passed to the network layer for processing for delivery to the desired location • The port number and sequence are contained in the TPDU header, number, acknowledgement number, checksum, and other information for different fields Flow Control: • The transport layer, like the data link layer, controls flow. • Flow control at the transport layer, on the other hand, is done final stage rather than node-to-node. • To manage flow, the Transport Layer employs a sliding window protocol. Error Control: • End-to-end error control is also provided through the transport layer. • The transport layer covers a variety of errors, including: • Damaged bits have caused an error. • Error due to TPDUs not being delivered. • Due to double distribution of TPDUs, an error has occurred. • Error due to TPDU delivery to the incorrect location. Error Control: • End-to-end error control is also provided through the transport layer. The transport layer is responsible for a variety of various sorts of data. • Damaged bits have caused an error. • Error due to TPDUs not being delivered. • Due to double distribution of TPDUs, an error has occurred. • Error due to TPDU delivery to the incorrect location. Controlling Congestion: • The transport layer also manages network congestion. • To avoid congestion, many different congestions control methods are utilised. The transport layer communicates with the session layer's functions, according to the tiered model. The application layer is a layer that combines the session, presentation, & application layer protocols it in to a single layer. Delivery to just the session layer in these circumstances refers to distribution to application layer. Data generated by one machine's application must 83 CU IDOL SELF LEARNING MATERIAL (SLM)

be sent to the correct machine's application. The transport layer is in charge of addressing in this scenario. The user address, which is given as a station or port, is provided by the transport layer. The port variable identifies a specific TS user of a Transport Service base station at a certain station (TSAP). There is only one transit entity per station.The transport layer protocols require information over which upper-layer protocols are being used. Figure 4.2 Communications between Transport Layers 4.4 TCP CONNECTION ESTABLISHMENT: TCP is a connection-oriented protocol, which means it must interface in order to grant resources on both sides of the communication. Establishing a Connection – 84 CU IDOL SELF LEARNING MATERIAL (SLM)

Figure 4.3 Communication Establishment The process begins with the sender doing the following: Sequence number (Seq=521): holds the sender's produced random start sequence number. Request that the receiver's sequence number be synchronised with the sequence number provided above (Syn=1). Maximum growth rate (MSS=1460 B): the sender specifies its maximum packet size so that the receiver can send a datagram that is fragment-free. The MSS field is found in the TCP header's Option field. Sender specifies the buffer capacity in that he must store messages from the receiver (window=14600 B).Because TCP is a full duplex protocol, both the sender and the receiver needs a window to receive messages.Sequence number (Seq=2000): includes the randomly generated start sequence number on the receiver side. Syn flag (Syn=1): asks the sender to synchronise its sequence number only with sequence number provided above.Maximum segment length (MSS=500 B): the sender specifies the maximum segment size so that the receiver can send a datagram without fragmentation. The MSS field is found in the TCP header's Option field. 85 CU IDOL SELF LEARNING MATERIAL (SLM)

Because MSS receiver is MSS sender, both sides agree on a minimum MSS of 500 bytes to minimise packet fragmentation at both ends.As a result, the receiver can only send 14600/500 = 29 packets.This is the size of the receiver's transmitting window. Window size (window=10000 B): the receiver specifies the size of the buffer in which he must store messages from the sender.As a result, the sender can only send a total of 10000/500 = 20 packets.This is the size of the sender's transmitting window. Since sequence number 521 has been received by the receiver, it submits a request for the following sequence number with Ack no. =522, and this is the next packet expected by the receiver because Syn flag consumes one sequence no.The ACK flag (ACk=1) indicates that the acknowledgement sequence gains various the next sequence that the recipient is expecting. The sender's final response for connection establishment is as follows: Sequence number (Seq=522): Since the first step's sequence number was 521, and the SYN flag consumes one, the very next data packet will be 522. Since the sender acknowledges a SYN=1 packet from the recipient with the sequence number 2000, the first sequence number expected is 2001. The acknowledgement number field includes the next sequences expected by the sender, according to the ACK flag (ACK=1). TCP's connection establishment phase is often called as 3-way Handshaking (SYN, SYN + ACK, ACK) since it uses three packets. 4.5 FLOW CONTROL IN TRANSPORT LAYER: Flow control - The transport layer of the TCP/IP paradigm offers a flow control technique between the adjacent layers. TCP also employs flow control techniques to prevent data loss caused by a fast transmitter and a slow receiver. It employs the sliding window protocol, in which the receiver sends a window receiver to the person indicating the maximum amount of data it can accept. Flow control is being used to keep the sender from sending too much data to the recipient. When a receiver is overwhelmed with data, it discards packets and requests that they be retransmitted. As a result, network congestion grows, lowering system performance. Flow control is handled by the transport layer. It employs the sliding window protocol, which improves data transmission efficiency while also controlling data flow to avoid overloading the receiver. Instead of being frame-oriented, the sliding window protocol is byte-oriented. TCP is the strategy that provides that we can communicate reliably over an unstable network. Packets can be lost, arrive out of sequence, the network could be crowded, or even the receiver node could be overloaded when sending data from one node to another. When creating an application, however, we normally don't have to cope with this complexity; 86 CU IDOL SELF LEARNING MATERIAL (SLM)

instead, we simply write data to a socket, and TCP ensures that the packets arrive to the recipient node correctly. TCP also provides what is known as Flow Control, which is a crucial service. Figure 4.4 Flow Control TCP's Flow Control feature ensures that a sender does not overload a receiver by sending packets quicker than it can ingest. Back pressure is a term used in the Distributed Systems field to describe something similar. The concept would be that a node receiving information will provide some form of feedback to the node delivering the data, informing it of its present state. It's vital to note that it is not the same with traffic management. Although the mechanisms used by TCP to deliver both services have considerable overlap, they are different aspects. Congestion control is needed to minimize a node from overpowering the network (i.e., the connections between nodes), whereas Flow Control is concerned with the end-node. How does it work? This is what happens most of the time when we need to communicate data over a network. 87 CU IDOL SELF LEARNING MATERIAL (SLM)

The sender application publishes data to a socket, and the transport layer (in this case, TCP) wraps this data in a segment before passing it to the network layer (e.g., IP), which will route the packet to the receiving node. Figure 4.5 TCP Flow Control The network layer will transmit this piece of data to TCP, which will allow access to the recipient application as an exact replica of the data sent, meaning it will not transmit packets out of order but will allow time for a retransmission if a gap in the byte stream is detected. The data that TCP needs to communicate is stored in the transmit buffer, and the data that it receives is stored in the receive buffer. Whenever the application is ready, data from either the receive buffer will be read. When the receive buffer has been full, Flow Control ensures that we don't transmit any more packets, as the receiver won't be capable of handling them and will have to drop them. 88 CU IDOL SELF LEARNING MATERIAL (SLM)

Figure 4.6 Received TCP Buffer The receiver would advertise its Receive Window (rwnd), or the free space in the receive buffer, to limit the amount of data TCP can broadcast. When TCP receives a packet, it must send such ack message to the sender acknowledging that it received the packet correctly, as well as the current receive window value, so the sender knows if it can continue sending data. 4.6 MULTIPLEXING AND DEMULTIPLEXING Multiplexing is the process of gathering data from several sender application processes, wrapping it in a header, and transmitting it all at once to the designated recipient. Demultiplexing is the process of delivering received segments to the correct app layer operations at the receiver side. 89 CU IDOL SELF LEARNING MATERIAL (SLM)

Figure 4.7 Multiplexing/Demultiplexing Multiplexing and demultiplexing are divided into two categories: Multiplexing and demultiplexing without connections Connection-oriented multiplexing or demultiplexing 90 CU IDOL SELF LEARNING MATERIAL (SLM)

Figure 4.8 Multiplexing Process The Process of Multiplexing and Demultiplexing - To send data from a sender-side application to a destination-side application, the sender must understand the destination's IP address and the port number of such application (just at destination side) toward which he wants to transmit the data. Let's take a look at two popular messaging apps these days: Hike and WhatsApp. Let's pretend that A is the sender and B is the recipient. Both the sender and the recipient have these programmes installed on their computers (say smartphone). Assume A has sent messages to B using WhatsApp while also hiking. To do so, A must include B's IP address and the WhatsApp application's target port number when sending a message through the WhatsApp application. In the latter situation, A must include B's IP address and the hike's destination port number while delivering the message. 91 CU IDOL SELF LEARNING MATERIAL (SLM)

Figure 4.9 Communications of Different Ports The messages from both apps will now be bundled together with relevant headers (such as source IP address, destination IP address, source port number, and destination port number) and transmitted to the receiver as a single message. Multiplexing is the term for this procedure. The received message also has is unwrapped at the destination, and constituent messages (e.g., messages from the hiking and WhatsApp applications) are forwarded to the application interface by looking up the port number at the destination. Demultiplexing is the term for this procedure. Similarly, B has the ability to send messages to A. Figure 4.10: Multiplexing Multiplexing can take place in one of two ways: Multiple transport layer connections using the same network connection is known as upward multiplexing. The transport layer uses upward multiplexing to send numerous transmissions intended because of the same destination down the same path, making it more cost-effective. 92 CU IDOL SELF LEARNING MATERIAL (SLM)

Figure 4.11 Upward Multiplexing Downward multiplexing refers to the utilisation of numerous network connections by one transport layer link. Downward multiplexing enables the transport layer to divide a connection into many pathways in order to increase throughput. When networks have a limited or slow capacity, this sort of multiplexing is used. Figure 4.12 Downward Multiplexing 93 CU IDOL SELF LEARNING MATERIAL (SLM)

4.7 SUMMARY • In the OSI model, the transport layer receives user data to the application layer & prepares it for transit through many devices. It also prepares its data for network layer transmission. The transport layer is in charge of getting application information from the device to the destination. The segment is the PDU used in this tier. • The transport layer is in charge of segmenting and controlling the numerous communication streams, as well as putting the communication together at the recipients' end. • From the source to the destination, communication between both the upper (application layer) & lower (network layer) is tracked. This implies it distinguishes between the various programmes and the packets received from either the network layer. • Application data from the sender is segmented. The segment is indeed the transport layer PDU, as previously stated. • The individual portions are reassembled into the various applications only at recipients. • Differentiating and identifying the various uses. • The TCP (Transmission Control Protocol) as well as the (UDP) User Datagram Protocol are the two fundamental protocols in the TCP/IP protocol family. There are a number of other protocols which are governed by these protocols. 4.8 KEYWORDS • Multiplexing-Multiplexing is the process of gathering data from several sender application processes, wrapping it in a header, and transmitting it all at once to the designated recipient. • Demultiplexing-Demultiplexing is the process of delivering received segments to the correct app layer operations at the receiver side. 4.9 LEARNING ACTIVITY 1. You need to configure a server that is on the subnet 192.168.19.24/29. The router has the first available host address. Which IP address you will assign to the server? ___________________________________________________________________________ _______________________________________________________________ 94 CU IDOL SELF LEARNING MATERIAL (SLM)

2. Consider an instance of TCP’s Additive Increase Multiplicative Decrease (AIMD) algorithm where the window size at the start of the slow start phase is 2 MSS and the threshold at the start of the first transmission is 8 MSS. Assume that a timeout occurs during the fifth transmission. Find the congestion window size at the end of the tenth transmission. ___________________________________________________________________________ _______________________________________________________________ 4.10UNIT END QUESTIONS A. Descriptive Questions Short Questions 1. What is connection management in transport layer? 2. Write the functions of transport layer 3. What is RIP? 4. What is neighbour table? 5. What is multiplexing? Long Questions 1. Explain the responsibilities of Transport layer. 2. Discuss about transport layer design issues. 3. Discuss the error control in transport layer. 4. Explain about TCP connection establishment 5. Compare Multiplexing and demultiplexing. B. Multiple Choice Questions 1. Downward ____ refers to the utilisation of numerous network connections by one transport layer link. a. Multiplexing b. Routing Protocol c. Demultiplexing d. link state routing 2. _____ is being used to keep the sender from sending too much data to the recipient 95 CU IDOL SELF LEARNING MATERIAL (SLM)

a. Error control b. RARP c. Flow control d. Transmission 3. Which table provides information about the router's neighbours? a. Prompt b. Design c. Protocol d. Neighbour 4. _____ holds the sender's produced random start sequence number. a. flow number b. sequence number c. topology d. random number 5. OSPF routing enables you to keep databases that include information about the ____ a. network's topology b. Preference c. Distance vector d. entire topology Answers 1-a, 2-c, 3-d, 4- b, 5- a 4.11 REFERENCES Reference books • Behrouz A Forouzan, “Data Communications and Networking”, McGraw Hill. • Andrew S. Tanenbaum, “Computer Networks”, Pearson Education. 96 CU IDOL SELF LEARNING MATERIAL (SLM)

• Subir Kumar Sarkar, T.G. Basavaraju, C. Puttaamadappa, “AdHoc Mobile Wireless Network: Principles, Protocols, and Applications, CRC Press. Textbook references • James F. Kurose, Keith W. Ross, “Computer Networking”, Pearson Education. • Michael A. Gallo, William M. Hancock, “Computer Communications and Networking Technologies”, CENGAGE Learning Websites: • https://www.techopedia.com/definition/10062/wireless-communications • https://www.computernetworkingnotes.com/ • https://www.guru99.com 97 CU IDOL SELF LEARNING MATERIAL (SLM)

UNIT 5-TRANSPORT PROTOCOLS STRUCTURE 5.0 Learning Objectives 5.1 Introduction to Transport Protocols 5.2 Transport layer protocols 5.3 TCP 5.4 UDP 5.5 Difference between TCP and UDP 5.6 Summary 5.7 Keywords 5.8 Learning activity 5.9 Unit End Questions 5.10 References 5.0 LEARNING OBJECTIVES After studying this unit, you will be able to: • Explain the basics of Transport protocols • State TCP and its features • Describe UDP and its features • List the comparison of TCP and UDP 5.1 INTRODUCTION TO TRANSPORT PROTOCOLS The Internet allows any host computer to send packets (convenient data units for computers and routers) to one or so other host computers. The network protocols, on the other hand, give no promises on packet delivery. In fact, a packet could be misplaced, arrive after others that were sent later, or be deformed. It's possible that a packet will arrive that was never despatched! To combat this, host computers include transport protocols that use the Internet to transfer application information while also sending a range of other data for error checking, correction, and recovery. Based on the application needs, transport protocols come in a variety of levels of complexity. The following are three examples: UDP stands for User Datagram Protocol. 98 CU IDOL SELF LEARNING MATERIAL (SLM)

The UDP protocol is a \"send and forget\" protocol. It includes only enough control messages at the start of each transmission to determine which programme is running and whether the packet has been distorted during transmission. UDP is typically used by applications that don't require an answer and don't care if the message was received on the other end. A server that uninvitedly publishes the moment on the network is a good illustration of this. RDP stands for Reliable Data Protocol. RDP is a generic term for a group of protocols, the most significant of which is Prospero's (see later). RDP-type protocols are comparable to TCP, but with less complexity at the beginning and end of a discussion, and with great support for sequences of data transfers known as Remote Procedure Calls, or often wrongly referred to as transactions. TCP stands for Transmission Control Protocol. TCP is the protocol module that ensures security and reliability. TCP is built to handle a wide range of network faults and adapts gracefully to the network's available resources. It even makes an effort to be equitable to all users. 5.2 TRANSPORT LAYER PROTOCOLS: TCP and UDP are the two protocols that make up the transport layer. A datagram is delivered from a source host to a destination host via the IP protocol throughout the network layer. Today's operating systems offer multiuser where multiprocessing environments, and a process is a running programme. When a host delivers a message to another host, the source process is simply sending a process to the destination process. The transport layer protocols specify some protocol ports, which are links to particular ports. An IP protocol is a host-to-host protocol that delivers a packet from one host to another, whereas transport layer protocols were also port-to-port protocols that work on top of IP protocols to transfer packets from the originating port to IP services and from IP services to both the destination port. Each port has a 16-bit positive integer address that defines it. 99 CU IDOL SELF LEARNING MATERIAL (SLM)

Figure 5.1 Transmission of a Datagram 5.3 TCP Transmission Control Protocol (TCP) is an acronym for Transmission Control Protocol. It provides apps with full transport layer services. It is a connection-oriented protocol, which means that it establishes a connection between both transmission endpoints. TCP establishes a virtual circuit between the sender and the receiver and for duration of the communication. Transmission Control Protocol (TCP) is an acronym for Transmission Control Protocol. This is a transport layer option that enables packets to be sent from one location to another. It's a connection-oriented protocol, which implies it establishes the connection before the communication between the network's computer units. Because this protocol is used in conjunction with the IP protocol, they are referred to as TCP/IP. TCP Protocol Characteristics A TCP protocol has the following characteristics: TCP/IP (Transport Layer Protocol) is aTCP stands for transport layer protocol, and it is used to deliver data from a sender to a receiver. TCP is a dependable protocol because it adheres to a flow and error control mechanisms. It also aids the acknowledgment system, which verifies the data's condition and sound arrival. The receiver sends a positive or negative acknowledgment here to sender as part of the acknowledgment process so that the sender may determine if the data packet has indeed been received or whether it needs to be resent. 100 CU IDOL SELF LEARNING MATERIAL (SLM)