Data Communication PDF

Data Communication The term telecommunication means communication at a distance. The word data refers to information presented in whatever form is agreed upon by the parties creating and using the data. Data communications are the exchange of data between two devices via some form of transmission me...

Data Communication The term telecommunication means communication at a distance. The word data refers to information presented in whatever form is agreed upon by the parties creating and using the data. Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable. 1 1 Physical Structures Type of Connection Point to Point - single transmitter and receiver Multipoint - multiple recipients of single transmission Physical Topology Connection of devices Type of transmission - unicast, mulitcast, broadcast 2 2 Advantages of Mesh topology  No data loss  Reliable  Secure  Easy to troubleshoot  Fast communication 3 Mesh Topology 4 Mesh Topology  In mesh topology each device is connected to every other device on the network through a dedicated point-to-point link.  When we say dedicated it means that the link only carries data for the two connected devices only.  Lets say we have n devices in the network then each device must be connected with (n-1) devices of the network.  Number of links in a mesh topology of n devices would be n(n-1)/2. 5 Network Criteria Performance Depends on Network Elements Measured in terms of Delay and Throughput Reliability Failure rate of network components Measured in terms of availability/robustness Security Data protection against corruption/loss of data due to: Errors Malicious users 6 6 Star Topology 7 Disadvantages of Star topology  If hub goes down everything goes down.  Hub requires more resources and regular maintenance.  Not Scalable 8 Disadvantages of bus topology  Difficultly in fault detection.  Not scalable  Difficult to troubleshoot  Data collision 9 ISO/OSI reference model presentation: allow applications to interpret application meaning of data, e.g., presentation encryption, compression, machine-specific conventions session session: synchronization, transport check pointing, recovery of data exchange network Internet stack “missing” these link layers! physical these services, if needed, must be implemented in application needed? 10 Internet protocol stack application: supporting network applications FTP, SMTP, HTTP application transport: process-process data transfer transport TCP, UDP network: routing of datagrams network from source to destination IP, routing protocols link: data transfer between link neighboring network elements Ethernet, 802.111 (WiFi), PPP physical physical: bits “on the wire” 11 Ring Topology  Each device is connected with the two devices on either side of it.  There are two dedicated point to point links a device has with the devices on the either side of it.  This structure forms a ring thus it is known as ring topology.  If a device wants to send data to another device then it sends the data in one direction.  each device in ring topology has a repeater.  if the received data is intended for other device then repeater forwards this data until the intended device receives it. 12 PROTOCOLS A protocol is synonymous with rule. It consists of a set of rules that govern data communications. It determines what is communicated, how it is communicated and when it is communicated. The key elements of a protocol are syntax, semantics and timing Topics discussed in this section:  Syntax  Semantics  Timing 13 Client-server architecture server: always-on host permanent IP address data centers for scaling clients: communicate with server may be intermittently client/server connected may have dynamic IP addresses do not communicate directly with each other 14 Reliable and Unreliable Connections The transport layer uses reliable and unreliable connections to transfer data between two devices in a network. A reliable connection provides guaranteed data delivery, but it takes more time for data delivery than an unreliable connection. For reliable connections, it uses TCP (Transmission Control Protocol). The TCP protocol uses a three-way handshake, windowing, and sequence numbers for guaranteed data delivery. An unreliable connection delivers data faster than a reliable connection, but it does not provide any guarantee for data delivery. 15 Connectionless protocol In a network system, connectionless service is used to send data from one end to the other without establishing a connection. As a result, there is no need to establish a connection before delivering data from the As a result, we might conclude transmitter to the receiver. that the data packet does not follow a predefined path. It is not a dependable network service since it Due to network congestion, does not guarantee the the transmitted data packet is passage of data packets to not received by the recipient the recipient, and data in connectionless service, and packets can arrive at the the data may be lost. receiver in any sequence. Example: UDP, IP protocols 16 P2P architecture no always-on server peer-peer arbitrary end systems directly communicate peers request service from other peers, provide service in return to other peers self scalability – new peers bring new service capacity, as well as new service demands peers are intermittently connected and change IP addresses complex management 17 Connection-oriented protocol A connection-oriented service is a network service that before delivering data over the same or separate networks, a connection- oriented service is used to establish an end-to-end connection between the It employs a handshake sender and the receiver. approach to establish a connection between the user Packets are forwarded to and the sender before the receiver in the same delivering data across the sequence as they were network. sent by the sender. As a result, it is also recognized as a reliable network service. Example: TCP protocol 18 Application architectures 19  source message M application segment Ht M transport datagram Hn Ht M network frame Hl Hn Ht M link physical link physical Encapsulatio switch n destination Hn Ht M network M application Hl Hn Ht M link Hn Ht M Ht M transport physical Hn Ht M network Hl Hn Ht M link router physical 20 Categories of Networks Local Area Networks (LANs) Short distances Designed to provide local interconnectivity Wide Area Networks (WANs) Long distances Provide connectivity over large areas Metropolitan Area Networks (MANs) Provide connectivity over areas such as a city, a campus 21 Disadvantages of Ring Topology  A link failure can fail the entire network as the signal will not travel forward due to failure.  Data traffic issues, since all the data is circulating in a ring. 22 Advantages of Ring Topology  Easy to install.  Less expensive.  Easy maintenance. 23 Ring Topology 24 Advantages of Star topology  Less expensive  Easier to install  Cost effective  Robust  Easy to troubleshoot  Reliable 25 Bus Topology  In bus topology there is a main cable and all the devices are connected to this main cable through drop lines.  There is a device called tap that connects the drop line to the main cable.  Since all the data is transmitted over the main cable, there is a limit of drop lines and the distance a main cable can have. 26 Bus Topology  In bus topology there is a main cable and all the devices are connected to this main cable through drop lines.  There is a device called tap that connects the drop line to the main cable.  Since all the data is transmitted over the main cable, there is a limit of drop lines and the distance a main cable can have. 27 Bus Topology 28 Star Topology 29 Disadvantages of Mesh topology  Amount of wires required to connected each system is tedious and headache.  Since each device needs to be connected with other devices, number of I/O ports required must be huge.  Scalability issues because a device cannot be connected with large number of devices with a dedicated point to point link. 30 Figure 3 Types of connections: point-to-point and multipoint 31 31 Network Topology  Geometric representation of how the computers are connected to each other is known as topology. There are mainly four types of topology: ◦ Mesh Topology ◦ Star Topology ◦ Bus Topology ◦ Ring Topology 32  NETWORKS A network is a set of devices (often referred to as nodes) connected by communication links. A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network. A link can be a cable, air, optical fiber, or any medium which can transport a signal carrying information. Topics discussed in this section:  Network Criteria  Physical Structures  Categories of Networks 33 33 Figure 1 Components of a data communication system 34 34 Figure 2 Data flow (simplex, half-duplex, and full-duplex) 35 35 Flow Control Flow control deals with the amount of data sent to the receiver side without receiving any acknowledgment. It makes sure that the receiver will not be overwhelmed with data. It’s a kind of speed synchronization process between the sender and the receiver. Flow Control The flow control mechanism tells the sender the maximum speed at which the data can be sent to the receiver device. The sender adjusts the speed as per the receiver’s capacity to reduce the frame loss from the receiver side. Stop and wait flow control Simplest form of flow control In Stop-and-Wait flow control, the receiver indicates its readiness to receive data for each packet. Operations: 1. Sender: Transmit a single packet 2. Receiver: Transmit acknowledgment (ACK) 3. Go to 1. Stop and wait flow control Stop and wait flow control  Disadvantage of Stop and Wait 2. Problems arise as a result of the lost acknowledgement One issue arises in this situation: The sender waits an endless time for an acknowledgement.  Disadvantage of Stop and Wait 3. Problem resulting from delayed data or acknowledgement The data was sent by the sender and was also received by the recipient. The acknowledgement is then sent by the recipient, but it is not received until the timeout period has passed on the sender’s end. Due to the acknowledgement being received after this, it can be mistaken for acknowledging the receipt of another data packet. Introduction to Sliding Window One of the popular flow control mechanisms in TCP is the sliding window protocol. It’s a byte-oriented process of variable size. In this method, when we establish a connection between the sender and the receiver, the receiver sends the receiver window to the sender. The receiver window is the size that is currently available in the receiver’s buffer. Introduction to Sliding Window Introduction to Sliding Window From the available receiver window, TCP calculates how much data can be sent further without acknowledgment. Although, if the receiver window size is zero, TCP halts the data transmission until it becomes a non-zero value. The receiver window size is the part of the frame of TCP segments. The length of the window size is 16 bits, which means that the maximum size of the window is 65,535 bytes. The receiver decides the size of the window. The receiver sends the currently available receiver window size with every acknowledgment message.  TCP Flow Control There are two flow control mechanisms that are built on sliding window: Go-Back-N Selective Repeat Go-back-N Go-Back-N is an automatic repeat request (ARQ) protocol used in data communication to ensure reliable data transmission over an unreliable channel. Go-Back-N relies on a sliding window approach, where the sender can transmit a sequence of data frames before needing an acknowledgment (ACK) from the receiver. If a frame is lost or received with errors, the sender “goes back” to the beginning of the window and retransmits all the frames from that point onward. Go-back-N Example Selective Repeat Selective Repeat Congestion Control in TCP Congestion is an important factor in packet- switched networks. It refers to the state of a network where the message traffic becomes so heavy that the network response time slows down leading to the failure of the packet. TCP congestion control refers to the mechanism that prevents congestion from happening or removes it after congestion takes place. Receiver window size shows how much data can a receiver receive in bytes without giving any acknowledgment Congestion window state of TCP that limits the amount of data to be sent by the sender into the network even before receiving the TCP Congestion Control Slow Start In the slow start phase, the sender sets at the initial stage: congestion window size = maximum segment size (1 MSS) The sender increases the size of the congestion window by 1 MSS after receiving the ACK (acknowledgment). The size of the congestion window increases exponentially in this phase. The formula for determining the size of the congestion window is: Congestion window size = Congestion window size + Maximum segment size This phase continues until window size reaches its slow start threshold. Slow Start Congestion Avoidance In this phase, after the threshold is reached, the size of the congestion window is increased by the sender linearly in order to avoid congestion. Each time an acknowledgment is received, the sender increments the size of the congestion window by 1. This phase continues until the size of the window becomes equal to that of the receiver window size. Congestion Avoidance Congestion Detection In this phase, the sender identifies the segment loss and gives acknowledgment depending on the type of loss detected. Case1: Detection On Time Out Case 2: Detection Of Receiving 3 Duplicate Ack Congestion Detection Case1: Detection On Time Out In this, the timer time-out expires even before receiving acknowledgment for a segment. It suggests a stronger possibility of congestion in a network. In this, there are chances that a segment has been dropped in the network Reaction in response to Detection on time out: Setting the threshold to start at half of the current size of the window Decreasing the size of the congestion window to MSS Slow start phase is resumed Congestion Detection Case 2: Detection Of Receiving 3 Duplicate Ack This case suggests the weaker possibility of congestion in the network. In this case, the sender receives three duplicate ack for a network segment. The chances are that fewer segments have dropped while the one sent later might have reached. Reaction on receiving 3 duplicate acknowledgments: Setting the threshold to start at half of the current size of the window Decreasing the size of the congestion window to that of the slow start threshold NAT Protocol One public IP address is needed to access the Internet. But we can use a private IP address in our private network. The idea of NAT is to allow multiple devices to access the Internet through a single public address. To achieve this, a private IP address must be translated into a public IP address. 60 NAT Protocol What is Network Address Translation(NAT)? NAT is a process in which one or more local IP addresses are translated into one or more Global IP addresses and vice versa to provide Internet access to the local hosts. NAT is critical in allowing communication between devices in the contemporary networking world. NAT is a crucial technology that allows several devices on a network to share a 61 NAT Protocol At its core, NAT acts as a translator, mediating the exchange of data packets between devices within a local network and external networks, such as the internet. 62 NAT Protocol Working of Network Address Translation (NAT) Generally, the border router is configured for NAT i.e. the router which has one interface in the local (inside) network and one interface in the global (outside) network. When a packet traverse outside the local (inside) network, then NAT converts that local (private) IP address to a global (public) IP address. When a packet enters the local network, the global (public) IP address is converted to a local (private) IP address. 63 Types of NAT translation NAT encompasses various translation types that cater to diverse networking requirements: Static NAT Dynamic NAT Overloading (Port Address Translation - PAT) 64 Static NAT 65 Dynamic NAT Dynamic NAT dynamically allocates public IP addresses from a pool of available addresses to devices within the local network on a first-come, first-served basis. It optimizes the use of available addresses by allowing multiple devices to share a smaller pool of public IP addresses. 66 Dynamic NAT 67 Port Address Translation Port Address Translation (PAT), maps multiple private IP addresses to a single public IP address using unique port numbers. By leveraging different port numbers for internal devices, PAT effectively distinguishes between devices, managing incoming and outgoing data traffic. 68  Challenges and limitations of NAT End-to-End Connectivity Application Compatibility Scalability Concerns Impact on IPsec VPNs NAT Logging and Troubleshooting 69 Traditional Connectivity 70 What is VPN? Virtual Private Network is a type of private network that uses public telecommunication, such as the Internet, instead of leased lines to communicate. Became popular as more employees worked in remote locations. Terminologies to understand how VPNs work. 71 Virtual Private Networks Employees can access the network (Intranet) from remote locations. Secured networks. The Internet is used as the backbone for VPNs Saves cost tremendously from reduction of equipment and maintenance costs. Scalability 72 Remote Access Virtual Private Network 73 How it Works Two connections : one is made to the Internet and the second is made to the VPN. Datagrams : contains data, destination and source information. Firewalls : VPNs allow authorized users to pass through the firewalls. Protocols : protocols create the VPN tunnels. 74 VPN Critical Functions Authentication – validates that the data was sent from the sender. Access control – limiting unauthorized users from accessing the network. Confidentiality – preventing the data to be read or copied as the data is being transported. Data Integrity – ensuring that the data has not been altered 75 Encryption Encryption : is a method of “scrambling” data before transmitting it onto the Internet. Public Key Encryption Technique Digital signature –> for authentication 76 Tunneling A virtual point-to-point connection made through a public network. It transports encapsulated datagrams. Original Datagram Encrypted Inner Datagram Datagram Header Outer Datagram Data Area Two types of end points:  Remote Access  Site-to-Site 77 Four Protocols used in VPN  PPTP -- Point-to-Point Tunneling Protocol  L2TP -- Layer 2 Tunneling Protocol  IPsec -- Internet Protocol Security  SOCKS – is not used as much as the ones above 78 VPN Encapsulation of Packets 79  Types of Implementations What does “implementation” mean in VPNs? There are three types Intranet : Within an organization Extranet : Outside an organization Remote Access : Employee to Business 80 Virtual Private Networks (VPN) Basic Architecture 81 Device Types There are three types:  Hardware  Firewall  Software 82 Device Types: Hardware Usually a VPN type of router Pros Cons Highest network throughput Cost Plug and Play Lack of flexibility Dual-purpose 83  Device Types: Firewall More security? Pros Cons “Harden” Operating System Still relatively costly Tri-purpose Cost-effective 84 Device Types: Software Ideal for 2 end points not in same org. Great when different firewalls implemented Pros Cons Flexible Lack of efficiency Low relative cost More labor training required Lower productivity; higher labor costs 85  Advantages: Cost Savings Eliminating the need for expensive long-distance leased lines Reducing the long-distance telephone charges for remote access. Transferring the support burden to the service providers Operational costs 86  Advantages: Scalability Flexibility of growth Efficiency with broadband technology 87  Disadvantages VPNs require an in-depth understanding of public network security issues and proper deployment of precautions Availability and performance depends on factors largely outside of their control VPNs need to accommodate protocols other than IP and existing internal network technology 88  Applications: Site-to-Site VPNs Large-scale encryption between multiple fixed sites such as remote offices and central offices Network traffic is sent over the branch office Internet connection This saves the company hardware and management expenses 89 Site-to-Site VPNs 90 Applications: Remote Access Encrypted connections between mobile or remote users and their corporate networks Remote user can make a local call to an ISP, as opposed to a long distance call to the corporate remote access server. Ideal for a telecommuter or mobile sales people. VPN allows mobile workers & telecommuters to take advantage of broadband connectivity. i.e. DSL, Cable 91  Industries That May Use a VPN  Healthcare: enables the transferring of confidential patient information within the medical facilities & health care provider  Manufacturing: allow suppliers to view inventory & allow clients to purchase online safely  Retail: able to securely transfer sales data or customer info between stores & the headquarters  Banking/Financial: enables account information to be transferred safely within departments & branches  General Business: communication between remote employees can be securely exchanged 92 Summary of Network layer functions IP Addresses in a Network IP Address: 32-Bit Binary Number Classful IP Addressing Limitations to Classful Addressing Classless Inter-domain Routing (CIDR) Advantages of CIDR More efficient use of IPv4 address space Route summarization reduce routing table size reduce routing update traffic Classless Inter-domain Routing (CIDR) The concept of Routing Scaling connectivity requires Routing Routing IP Forwarding Router decides which interface a packet is sent to Forwarding table populated by routing process Forwarding decisions: destination address class of service (fair queuing, precedence, others) local requirements (packet filtering) Forwarding is usually aided by special hardware Static routing Static Routing Scenarios Static Route Configuration Advantages and Disadvantages of Static routing Characteristics of Dynamic Routing Dynamic routing protocols fulfill the following functions: Dynamically share information between routers Automatically update routing table when topology changes Determine best path to a destination Classifying Routing Protocols Classifying Routing Protocols Autonomous System (AS) Definition of Terms Routing flow and packet flow Routing policy Routing policy Example What Is an IGP? What Is an EGP? IGP versus EGP Dynamic routing Protocol Are used to automatically provide the best route for a remote network. Main Categories of Dynamic Routing Protocols: Interior Gate way Protocols (IGP): Used for routing within an Autonomous System(AS), (for example , organization , ISP…etc) Exterior Gateway Protocols (EGP): Used for routing between different Autonomous Systems. Dynamic routing Protocol Interior gateway Protocol Distance Vector The Distance vector algorithm is iterative, asynchronous and distributed. Distributed: It is distributed in that each node receives information from one or more of its directly attached neighbors, performs calculation and then distributes the result back to its neighbors. Iterative: It is iterative in that its process continues until no more information is available to be exchanged between neighbors. Asynchronous: It does not require that all of its nodes operate in the lock step with each other. The Distance vector algorithm is a dynamic algorithm. Each router maintains a distance table known Distance Vector Key features Knowledge about the whole network: Each router shares its knowledge through the entire network. The Router sends its collected knowledge about the network to its neighbors. Routing only to neighbors: The router sends its knowledge about the network to only those routers which have direct links. The router sends whatever it has about the network through the ports. The information is received by the router and uses the information to update its own routing table. Information sharing at regular intervals: Within 30 seconds, the router sends the information to the neighboring routers. Distance Vector Distance Vector Distance Vector Link State Link state routing is a technique in which each router shares the knowledge of its neighborhood with every other router in the internetwork. Link State Knowledge about the neighborhood: Instead of sending its routing table, a router sends the information about its neighborhood only. A router broadcast its identities and cost of the directly attached links to other routers. Flooding: Each router sends the information to every other router on the internetwork except its neighbors. This process is known as Flooding. Every router that receives the packet sends the copies to all its neighbors. Finally, each and every router receives a copy of the same information. Information sharing: A router sends the information to every other router only when the change occurs in the information. Link State Link State Routing has two phases: Initial state: Each node knows the cost of its neighbors. Final state: Each node knows the entire graph. Each node uses Dijkstra's algorithm on the graph to calculate the optimal routes to all nodes. RIP RIP stands for Routing Information Protocol. RIP is an intra-domain routing protocol used within an autonomous system. Here, intra-domain means routing the packets in a defined domain, for example, web browsing within an institutional area. To understand the RIP protocol, our main focus is to know the structure of the packet, how many fields it contains, and how these fields determine the routing table. RIP RIP is based on the distance vector-based strategy, so we consider the entire structure as a graph where nodes are the routers, and the links are the networks. In a routing table, the first column is the destination, or we can say that it is a network address. The cost metric is the number of hops to reach the destination. The number of hops available in a network would be the cost. The hop count is the number of networks required to reach the destination. In RIP, infinity is defined as 16, which means that the RIP is useful for smaller networks 15 hops or small autonomous systems. The next column contains the address of the router to which the packet is to be sent to reach the destination. RIP How is hop count determined? When the router sends the packet to the network segment, then it is counted as a single hop. when the router 1 forwards the packet to the router 2 then it will count as 1 hop count. when the router 2 forwards the packet to the router 3 then it will count as 2 hop count. when the router 3 forwards the packet to router 4, it will count as 3 hop count. RIP RIP Message Format The message format is used to share information among different routers. The RIP contains the following fields in a message:  RIP Command: It is an 8-bit field that is used for request or reply. The value of the request is 1, and the value of the reply is 2. Version: Here, version means that which version of the protocol we are using. Suppose we are using the protocol of version1, then we put the 1 in this field. Reserved: This is a reserved field, so it is filled with zeroes. Family: It is a 16-bit field. As we are using the TCP/IP family, so we put 2 value in this field. Network Address: It is defined as 14 bytes field. If we use the IPv4 version, then we use 4 bytes, and the other 10 bytes are all zeroes. Distance: The distance field specifies the hop count, i.e., the number of hops used to reach the destination. RIP How does the RIP work? If there are 8 routers in a network where Router 1 wants to send the data to Router 3. Route 1, Route 2, and Route 3. RIP will choose the The Route 2 contains the route which has least number of hops, 2. the least number of where Route 1 contains 3 hops. hops, Route 3 contains 4 hops, RIP Suppose R1 wants to send the data to R4. There are two possible routes to send data from r1 to r2. As both the routes contain the same number of hops, 3, so RIP will send the data to both the routes simultaneously. This way, it manages the load balancing, and data reach the destination a bit faster. RIP Disadvantages of RIP In RIP, the route is chosen based on the hop count metric. If another route of better bandwidth is available, then that route would not be chosen. Route 2 is chosen as it has the least hop count. The Route 1 is free and data can be reached more faster; instead of this, data is sent to the Route 2 that makes the Route 2 slower due to the heavy traffic. This is one of the biggest disadvantages of RIP. RIP Disadvantages of RIP The RIP is a classfull routing protocol, so it does not support the VLSM (Variable Length Subnet Mask). The classfull routing protocol is a protocol that does not include the subnet mask information in the routing updates. It broadcasts the routing updates to the entire network that creates a lot of traffic. In RIP, the routing table updates every 30 seconds. Whenever the updates occur, it sends the copy of the update to all the neighbors except the one that has caused the update. The sending of updates to all the neighbors creates a lot of traffic. It faces a problem of Slow convergence. Whenever the router or link fails, then it often takes minutes to stabilize or take an alternative route; This problem is known as Slow convergence. RIP supports maximum 15 hops which means that the maximum 16 hops can be configured in a RIP RIP Advantages of RIP It is easy to configure It has less complexity The CPU utilization is less OSPF The OSPF stands for Open Shortest Path First. It is a widely used and supported routing protocol. It is an intradomain protocol, which means that it is used within an area or a network. It is an interior gateway protocol that has been designed within a single autonomous system. It is based on a link-state routing algorithm in which each router contains the information of every domain, and based on this information, it determines the shortest path. OSPF The goal of routing is to learn routes. The OSPF achieves by learning about every router and subnet within the entire network. Every router contains the same information about the network. The way the router learns this information by sending LSA (Link State Advertisements). These LSAs contain information about every router, subnet, and other networking information. Once the LSAs have been flooded, the OSPF stores the information in a link-state database known as LSDB. The main goal is to have the same information about every router in an LSDBs. OSPF OSPF divides the autonomous systems into areas where the area is a collection of networks, hosts, and routers. Like internet service providers divide the internet into a different autonomous system for easy management and OSPF further divides the autonomous systems into Areas. Routers that exist inside the OSPF In Area, the special router also exists. The special routers are those that are present at the border of an area, and these special routers are known as Area Border Routers. This router summarizes the information about an area and shares the information with other areas. OSPF All the areas inside an autonomous system are connected to the backbone routers, and these backbone routers are part of a primary area. The role of a primary area is to provide communication between different areas. OSPF How does OSPF work? There are three steps: Step 1: The first step is to become OSPF neighbors. The two connecting routers running OSPF on the same link creates a neighbor relationship. Step 2: The second step is to exchange database information. After becoming the neighbors, the two routers exchange the LSDB information with each other. Step 3: The third step is to choose the best route. Once the LSDB information has been exchanged with each other, the router chooses the best route to be added to a routing table based on the calculation of SPF. OSPF How a router forms a neighbor relationship? The first thing is happened before the relationship is formed is that each router chooses the router ID. Router ID (RID): The router ID is a number that uniquely identifies each router on a network. The router ID is in the format of the IPv4 address. There are few ways to set the router ID, the first way is to set the router ID manually and the other way is to let the router decides itself. OSPF OSPF Message Format Version: It is an 8-bit field that specifies the OSPF protocol version. Type: It is an 8-bit field. It specifies the type of the OSPF packet. Message: It is a 16-bit field that defines the total length of the message, including the header. Therefore, the total length is equal to the sum of the length of the message and header. Source IP address: It defines the address from which the packets are sent. It is a sending routing IP address. Area identification: It defines the area within which the routing takes place. Checksum: It is used for error correction and error detection. OSPF Authentication type: There are two types of authentication, i.e., 0 and 1. Here, 0 means for none that specifies no authentication is available and 1 means for pwd that specifies the password-based authentication. Authentication: It is a 32-bit field that contains the actual value of the authentication data. OSPF OSPF Packets There are five different types of packets in OSPF: Hello Database Description Link state request Link state update Link state Acknowledgment OSPF Hello packet The Hello packet is used to create a neighborhood relationship and check the neighbor's reachability. Therefore, the Hello packet is used when the connection between the routers need to be established. Database Description After establishing a connection, if the neighbor router is communicating with the system first time, it sends the database information about the network topology to the system so that the system can update or modify accordingly. OSPF Link state request The link-state request is sent by the router to obtain the information of a specified route. Suppose there are two routers, i.e., router 1 and router 2, and router 1 wants to know the information about the router 2, so router 1 sends the link state request to the router 2. When router 2 receives the link state request, then it sends the link-state information to router 1. Link state update The link-state update is used by the router to advertise the state of its links. If any router wants to broadcast the state of its links, it uses the link-state update. OSPF Link state acknowledgment The link-state acknowledgment makes the routing more reliable by forcing each router to send the acknowledgment on each link state update. For example, router A sends the link state update to the router B and router C, then in return, the router B and C sends the link- state acknowledgment to the router A, so that the router A gets to know that both the routers have received the link- state update. OSPF The device running the OSPF protocol undergoes the following states: Down: If the device is in a down state, it has not received the HELLO packet. Here, down does not mean that the device is physically down; it means that the OSPF process has not been started yet. Init: If the device comes in an init state, it means that the device has received the HELLO packet from the other router. 2WAY: If the device is in a 2WAY state, which means that both the routers have received the HELLO packet from the other router, and the connection gets established between the routers. OSPF Exstart: Once the exchange between the routers get started, both the routers move to the Exstart state. In this state, master and slave are selected based on the router's id. The master controls the sequence of numbers, and starts the exchange process. Exchange: In the exchange state, both the routers send a list of LSAs to each other that contain a database description. Loading: On the loading state, the LSR, LSU, and LSA are exchanged. Full: Once the exchange of the LSAs is completed, the routers move to the full state. Border Gateway Protocol BGPis an interdomain routing protocol It uses the path-vector routing. It is a gateway protocol that is used to exchange routing information among the autonomous system on the internet. It works on different autonomous systems, 154 BGP Autonomous Systems 155 BGP Autonomous Systems An autonomous system is a collection of networks that comes under the single common administrative domain. It is a collection of routers under the single administrative domain. For example, an organization can contain multiple routers having different locations, but the single autonomous number system will recognize them. 156 BGP Autonomous Systems Within the same autonomous system or same organization, we generally use IGP (Interior Gateway Protocol) protocols like RIP, IGRP, EIGRP, OSPF. Suppose we want to communicate between two autonomous systems. In that case, we use EGP (Exterior Gateway Protocols). 157 BGP Autonomous Systems The protocol that is running on the internet or used to communicate between two different autonomous number systems is known as BGP (Border Gateway Protocol). The BGP is the only protocol that is running on the internet backbone or used to exchange the routes between two different autonomous number systems. Internet service providers use the BGP protocol to control all the routing 158 BGP Features Open standard It is a standard protocol which can run on any window device. Exterior Gateway Protocol It is an exterior gateway protocol that is used to exchange the routing information between two or more autonomous system numbers. InterAS-domain routing It is specially designed for inter-domain routing, where interAS-domain routing means exchanging the routing information between two or more autonomous number system. 159 BGP Features Supports internet It is the only protocol that operates on the internet backbone. Classless It is a classless protocol. Incremental and trigger updates Like IGP, BGP also supports incremental and trigger updates. 160 BGP Features Path vector protocol The BGP is a path vector protocol. Here, path vector is a method of sending the routes along with routing information. Application layer protocol It is an application layer protocol and uses TCP protocol for reliability. Metric It has lots of attributes like weight attribute, origin, etc. BGP supports a very rich number of attributes that can affect the path manipulation process. 161 BGP Features Configure neighborhood relationship It sends updates to configure the neighborhood relationship manually. Suppose there are two routers R1 and R2. Then, R1 has to send the configure command saying that you are my neighbor. On the other side, R2 also has to send the configure command to R1, saying that R2 is a neighbor of R1. If both the configure commands match, then the neighborhood relationship will get developed between these two routers. 162 Path attributes The BGP chooses the best route based on the attributes of the path. the path-vector routing is used in the border gateway routing protocol, which contains the routing table that shows the path information. The path attributes provide the path information. The attributes that show or store the path information are known as path attributes. This list of attributes helps the receiving router to make a better decision while applying any policy. 163 Path attributes 164 BGP Neighbors BGP neighborship is similar to the OSPF neighborship, but there are few differences BGP forms the neighboring relationship with the help of the TCP connection on port number 179 and then exchanges the BGP updates. They exchange the updates after forming the neighbor relationship. In BGP, the neighbor relationship is configured manually. BGP neighbors are also known as BGP peers or BGP speakers. 165 BGP Neighbors There are two types of neighbor relationship: 1. IBGP (Internal BGP): If all the routers are neighbors of each other and belong to the same autonomous number system, the routers are referred to as an IBGP. 166 BGP Neighbors 2. EBGP (External BGP): If all the routers are neighbors of each other and they belong to the different autonomous number systems, then the routers are referred to as an EBGP. 167 BGP Tables There are three types of BGP tables: Neighbor table: It contains the neighbors who are configured by the administrator manually. The neighbor relationship has to be manually configured by using the neighbor command. BGP forwarding table: It contains all the routes advertised in BGP IP routing table: The IP routing table contains the best path routes required to reach the destination. 168 BGP Packets Open: When the router wants to create a neighborhood relation with another router, it sends the Open packet. Update: The update packet can be used in either of the two cases: 1.It can be used to withdraw the destination, which has been advertised previously. 2.It can also be used to announce the route to the new destination. 169 BGP Neighbors Keep Alive: The keep alive packet is exchanged regularly to tell other routers whether they are alive or not. For example, there are two routers, i.e., R1 and R2. The R1 sends the keep alive packet to R2 while R2 sends the keep alive packet to R1 so that R1 can get to know that R2 is alive, and R2 can get to know that R1 is alive. Notification: The notification packet is sent when the router detects the error condition or close the 170 connection. What is Multiprotocol Label Switching (MPLS)? MPLS is a switching mechanism used in wide area networks (WANs). MPLS uses labels instead of network addresses to route traffic optimally via shorter pathways. MPLS is protocol-agnostic and can speed up and shape traffic flows across WANs and service provider networks. By optimizing traffic, MPLS reduces downtime and improves speed and quality of service (QoS). 171 History of MPLS As the internet grew in popularity, organizations looked for an efficient way to perform packet forwarding. Bandwidth demands increased, but label-switching mechanisms struggled to handle the load. Traditional methods, such as IP switching and tag switching, require each router to independently determine a packet's next hop by inspecting its destination IP address before consulting its routing table. 172 History of MPLS This slow process involves hardware resources and introduces the potential of degraded performance for real-time applications, such as voice and video. Traditional routers needed to scale more effectively to meet the bandwidth needs of the modern internet and avoid slow speeds, jitter and packet loss. 173 History of MPLS In 1997, the Internet Engineering Task Force (IETF) Multiprotocol Label Switching working group formed to create standards to help fix the issues around internet traffic routing. MPLS was developed as an alternative to multilayer switching and IP over asynchronous transfer mode (ATM). MPLS routers don't look up routes in routing tables, which helps boost the speed of network traffic. As MPLS techniques were developed and adopted throughout the early 2000s, the protocol became widely adopted. 174 Components of MPLS MPLS is defined by its use of labels instead of network addresses. This factor drives the flexibility and efficiency of MPLS. A label is a four-byte -- 32-bit -- identifier that conveys the packet's predetermined forwarding path in an MPLS network. 175 Components of MPLS While a network address specifies an endpoint, a label specifies paths between endpoints. This latter capability enables MPLS to decide the optimal pathway route of a given packet. Labels can also contain information about QoS and a packet's priority level. 176 Components of MPLS MPLS labels consist of the following four parts: Label value: 20 bits. Experimental: 3 bits. Bottom of stack: 1 bit. Time to live: 8 bits. 177 Components of MPLS MPLS is multiprotocol, which means it can handle multiple network protocols. MPLS is highly versatile and unifying, as it provides mechanisms to carry a multitude of traffic, including Ethernet traffic. One of the key differentiators between MPLS and traditional routers is it doesn't need specialized or additional hardware. 178 Components of MPLS It forwards using labels, as opposed to network addresses. The label contains the service class, as well as the destination, of the packet. It operates between Layers 2 and 3 of the Open Systems Interconnection (OSI) model. It guarantees the bandwidth of paths. 179 How an MPLS network works In an MPLS network, packets are labelled by an ingress router -- a label edge router (LER) – As they enter a service provider's network. The first router to receive a packet calculates the packet's entire path upfront. It also conveys a unique identifier to subsequent routers using a label in the packet header. 180 How an MPLS network works Every prefix in a routing table receives a unique identifier, and the MPLS service tells routers exactly where to look in the routing table for a specific prefix. This mechanism speeds up communication and traffic hopping. 181 How an MPLS network works MPLS works between the following OSI model layers: Layer 2. The data-link layer, or switching level, which uses protocols such as Ethernet. Layer 3. The routing layer, which covers traffic routing. 182 How an MPLS network works MPLS label traffic is sent via a label-switched path (LSP) inserted between the Layer 2 and Layer 3 headers. Label switch routers (LSRs) interpret the MPLS labels -- not the full IP address of any traffic. MPLS forwards data packets to Layer 2 of the OSI model, rather than passing to Layer 3. For this reason, MPLS is informally described as operating at Layer 2.5. 183 MPLS routing terminology Label edge routers LERs: are the ingress or egress routers or nodes when an LSR is the first or last router in the path, respectively. LSRs label incoming data -- the ingress node -- or pop the label off the packet. Label-switched paths LSPs: are the pathways through which packets are routed. An LSP enables service providers to decide the best way to flow certain types of traffic within a private or public network. Label switch routers LSRs: read the labels and send labelled data on identified pathways. Intermediate LSRs are available if a packet data link needs to be corrected. 184 How an MPLS network works Pop. This mechanism removes a label and is usually performed by the egress router. Push. This mechanism adds a label and is typically performed by the ingress router. Swap. This mechanism replaces a label and is usually performed by LSRs between the ingress and egress routers. 185 Steps of an MPLS network traffic pathway A packet enters the network through an LER. The packet is assigned to a forwarding equivalence class (FEC). The FEC assignment depends on the type of data and the destination. FECs are used to identify packets with similar or identical characteristics. 186 Steps of an MPLS network traffic pathway The LER -- or ingress node -- applies a label to the packet and pushes it inside an LSP. The LER decides on which LSP the packet takes until it reaches its destination address. The packet moves through the network across LSRs. 187 Steps of an MPLS network traffic pathway When an LSR receives a packet, it carries out the Push, Swap and Pop actions. In the final step, the LSR -- or egress router -- removes the labels and then forwards the original IP packet toward its destination. 188 Benefits of MPLS Router hardware has improved significantly since the development of MPLS, but MPLS still offers important benefits QoS controls and reliability VPNs Agnostic protocol support Reduced latency and improved performance Scalability 189 Benefits of MPLS 1. QoS controls and reliability Services need to be able to meet service-level agreements that cover traffic latency, jitter, packet loss and downtime. Service providers and enterprises use MPLS to implement QoS by defining LSPs that can meet the specific needs of a service. For example, a network might offer three service levels, each prioritizing different types of traffic -- e.g., one level for voice, one for time-sensitive traffic and one for best-effort traffic. 190 Benefits of MPLS 2. VPNs MPLS supports traffic separation and the creation of virtual private networks (VPNs), virtual private local area network services and virtual leased lines. 3. Agnostic protocol support MPLS is not tied to any specific protocol or transport medium. MPLS supports transport over IP, Ethernet, ATM and frame relay. An LSP can be created using any protocol. Generalized MPLS extends MPLS, which manages time-division multiplexing, and other classes of switching technologies beyond packet switching. 191 Benefits of MPLS 4. Reduced latency and improved performance MPLS is ideal for latency-sensitive applications, such as those handling videos, voice and mission-critical data. In addition, MPLS reduces latency by routing data more quickly using shorter path labels. To optimize performance, different types of data can be preprogrammed with other priorities and classes of service. Organizations can assign different bandwidth percentages for various kinds of data to ensure optimal delivery and access. 192 Benefits of MPLS 5. Scalability MPLS networks are scalable. Companies can provision and pay for only the bandwidth they need until their requirements change. 193 MPLS and security If MPLS is correctly configured, the security is comprehensive. In addition, MPLS connections are over a private, dedicated network, which creates customer isolation and helps ensure privacy. MPLS traffic isn't usually encrypted, but packets' labelling improves security through unique identifiers and isolation. 194 MPLS and security Organizations should use additional security measures to ensure MPLS networks are secured. Extra security best practices should include a defense-in- depth approach that uses measures such as denial-of- service prevention, firewalls to filter out malicious packets and authentication protocols to limit access. A best practice is to use a VPN tunnel between the provider edge routers and customer edge routers. 195  Agenda Digital Transformation Data Centers Virtualization What is Cloud computing Cloud computing deployment models Cloud computing service models 196 Digital Transformation Digital transformation is the process that an organization applies to integrate digital technology in all areas of a business, fundamentally changing how it delivers value to customers. Companies adopt innovative digital technologies to make cultural and operational shifts that adapt better to changing 197 customer demands. Digital Transformation cont. Examples Companies start building digital solutions, like mobile applications or an E-Commerce platform. Companies migrate from on-premises computer infrastructure to cloud computing. Companies adopt smart sensors to reduce operation costs. 198  Why Digital Transformation? Today, no enterprise is an island because of market force demands and unprecedented technology disruptions. 199 Why Digital Transformation? The term " digital transformation " describes the implementation of new technologies, talents, and processes to remain competitive in an ever- changing technology landscape. In the post-pandemic era, an organization must have the ability to adapt fast to changes like these: Time-to-market pressures Sudden supply chain disruptions Rapidly changing customer expectations Companies have to embrace digital transformation strategies if they want to 200 keep pace with technological developments. Benefits of Digital Transformation 201 Data Centers Data center (DC) is a physical facility that enterprises use to house computing and storage infrastructure in a variety of networked formats. Size of typical data centers: 500 – 5000 sqm buildings 1 MW to 10-20 MW power (avg 5 MW) 202 Traditional Data Center Architecture Servers mounted on 19’’ rack cabinets Racks are placed in single rows forming corridors between them. 203 Src: the datacenter as a computer – an introduction to the design of warehouse-scale machines Modern Data Centers 204 Costs for operating a data center 205 What is Virtualization? Virtualization is technology that you can use to create virtual representations of servers, storage, networks, and other physical machines. Virtual software mimics the functions of physical hardware to run multiple virtual machines simultaneously on a single physical machine. Businesses use virtualization to use their hardware resources efficiently and get greater returns from their investment. It also powers cloud computing services that help organizations manage infrastructure more efficiently. 206 What is Virtualization? Virtualization Virtualization is an abstraction of logical resources away from underlying physical resources. Virtualization technique shift OS onto hypervisor. Multiple OS share the physical hardware and provide different services. Improve utilization, availability, security and convenience. 207 CLOUD COMPUTING What is cloud computing? Cloud computing refers to the delivery of computing services over the internet, including storage, processing power, and software applications. It allows users to access resources and services on-demand, without the need for physical infrastructure or local servers. 208 Cloud Definition Definition from NIST (National Institute of Standards and Technology)  Cloud computing is a model for enabling convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction.  This cloud model promotes availability and is composed of five essential characteristics, three service models, and four deployment models. 209 CHARACTERISTICS OF CLOUD COMPUTING On-Demand Self-Service: Users can provision resources and services as needed, without requiring human interaction with service providers. Broad Network Access: Services are accessible over the internet via standard protocols and devices. Resource Pooling: Computing resources are pooled together to serve multiple users, allowing for efficient utilization and scalability. Rapid Elasticity: Resources can be scaled up or down quickly to meet changing demands. Measured Service: Cloud service usage is measured, monitored, and billed based on actual consumption. 210 CLOUD DEPLOYMENT MODELS Public Cloud Services are provided over a public network and available to anyone who wants to use them. It is a cost-effective option for businesses and individuals looking for scalability and flexibility. Public cloud providers, such as AWS, Azure, offer a wide range of services accessible to the general public. 211 CLOUD DEPLOYMENT MODELS Private Cloud Infrastructure is dedicated to a single organization and may be located on-premises or off-premises. Private cloud environments are designed to meet specific security, compliance, or performance requirements. They offer enhanced control, customization, and privacy but require significant upfront investment. 212 CLOUD DEPLOYMENT MODELS Hybrid Cloud Combines public and private cloud environments, allowing for flexibility and data sharing between the two. Organizations can leverage the benefits of both public and private clouds, ensuring optimal resource allocation. Hybrid cloud deployments enable workload portability and seamless integration between different environments. 213 CLOUD DEPLOYMENT MODELS Community Cloud Community cloud is a deployment model where infrastructure and services are shared among a specific community or group of organizations. It caters to the needs of a particular community, such as government agencies, educational institutions, or research organizations. Community cloud provides a cost-effective solution while addressing specific requirements and compliance standards of the community. 214 CLOUD SERVICE MODELS What if you want to have an IT department ? Similar to build a new house in previous analogy You can rent some virtualized infrastructure and build up your own IT system among those resources, which may be fully controlled. Technical speaking, use the Infrastructure as a Service (IaaS) solution. Similar to buy an empty house in previous analogy You can directly develop your IT system through one cloud platform, and do not care about any lower level resource management. Technical speaking, use the Platform as a Service (PaaS) solution. Similar to live in a hotel in previous analogy 215 You can directly use some existed IT system solutions, which were provided by some cloud application service provider, without knowing any detail technique about how CLOUD SERVICE MODELS 216 CLOUD SERVICE MODELS 217 Infrastructure as a service (IaaS) IaaS provides virtualized computing resources over the internet. Users have control over the operating systems, storage, and networking components. They can provision and manage virtual machines (VMs), storage, and networks according to their requirements. Examples include AWS, and Google Compute Engine. 218 Platform as a Service(PaaS) PaaS offers a platform for developing, testing, and deploying applications. Users can focus on application development without worrying about infrastructure management. PaaS providers manage the underlying infrastructure, including servers, storage, and networking. Developers can leverage pre-configured environments, development frameworks, and deployment tools. Examples: Google App Engine, and Microsoft Azure. 219 Software as a Service (SaaS) Software as a Service - SaaS The capability provided to the consumer is to use the provider’s applications running on a cloud infrastructure. The applications are accessible from various client devices through a thin client interface such as a web browser (e.g., web-based email). The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, storage, or even individual application capabilities, with the possible exception of limited user-specific application configuration settings. Examples : Google Apps (e.g., Gmail, Google Docs, Google sites, 220 …etc) Microsoft Office 365. CLOUD SERVICE MODELS 221 DIFFERENCES between CLOUD SERVICE MODELS 222 Benefits of Cloud 223 COMMON CLOUD COMPUTING USE CASES Data Storage and Backup: Store and back up large amounts of data securely. Software Development and Testing: Rapidly create and deploy applications in a scalable environment. Web and Mobile Applications: Host web and mobile applications in the cloud for global accessibility. Big Data Analytics: Process and analyze vast amounts of data using cloud resources. Disaster Recovery: Maintain data backups and recovery plans in the cloud for business continuity. 224