Module 1 Part II Network archuitecture.pptx

Network architecture refers to the design and organization of a computer network, including the hardware, software, and protocols used to communicate between devices. It defines how data is transmitted, routed, and received over the network, and how devices are connected and communicate with each other.

Some common network architectures include:

1. Client-Server: Where devices act as clients requesting resources from a central server.
2. Peer-to-Peer (P2P): Where devices act as equals, sharing resources without a central server.
3. Hybrid: Combines elements of client-server and P2P architectures.
4. Distributed: Where resources are spread across multiple devices, and processing is done in parallel.
5. Hierarchical: Where devices are organized in a tree-like structure, with higher-level devices controlling lower-level ones.
6. Mesh: Where each device connects to every other device, forming a web-like structure.
7. Torus: Where devices form a doughnut-shaped structure, commonly used in high-performance computing.
8. Bus: Where devices connect to a central cable or backbone, commonly used in computer hardware.
9. Star: Where devices connect to a central device, like a hub or switch.
10. Fully Connected: Where each device connects to every other device, forming a complete graph.

Network architecture is a crucial aspect of computer networking, as it determines the performance, scalability, and security of the network.

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Network architecture can be divided into several layers, each with its own protocols and technologies:

1. Physical Layer (Layer 1): Defines the physical means of transmitting data, such as electrical signals, light waves, or radio waves.
2. Data Link Layer (Layer 2): Ensures error-free transfer of data frames between nodes on the same network, using protocols like Ethernet or Wi-Fi.
3. Network Layer (Layer 3): Routes data between different networks, using protocols like IP (Internet Protocol) and ICMP (Internet Control Message Protocol).
4. Transport Layer (Layer 4): Ensures reliable data transfer between devices, using protocols like TCP (Transmission Control Protocol) and UDP (User Datagram Protocol).
5. Session Layer (Layer 5): Establishes, manages, and terminates connections between applications, using protocols like NetBIOS and SSH.
6. Presentation Layer (Layer 6): Converts data into a format that can be understood by the receiving device, using protocols like SSL/TLS (Secure Sockets Layer/Transport Layer Security).
7. Application Layer (Layer 7): Supports functions like email, file transfer, and web browsing, using protocols like HTTP (Hypertext Transfer Protocol), FTP (File Transfer Protocol), and SMTP (Simple Mail Transfer Protocol).

Some other important network architecture concepts include:

- Network topology: The physical and logical arrangement of devices and connections.
- Network protocols: The set of

1. Network Architecture Definition Network Architecture Assumptions Expecting unexpected Understanding Motivations Design Principles Elements of Effective Architectures Role of Geographic Distribution Type of architecture

2. Network Architecture Network Architecture is the way network services and devices are structured together to serve the connectivity needs of client devices and applications. Computer Network Architecture is defined as the physical and logical design of the software, hardware, protocols, and media of the transmission of data. Simply we can say that how computers are organized and how tasks are allocated to the computer. Network architecture refers to the way network devices and services are structured to serve the connectivity needs of client devices. Network devices typically include switches and routers. Types of services include DHCP and DNS. Client devices comprise end-user devices, servers, and smart things.

3. Network architecture There are many ways to approach network architecture design, which depend on the purpose and size of the network. Wide area networks (WAN), for example, refer to a group of interconnected networks often spanning large distances. Its network architecture will be vastly different from that of a local area network (LAN) of a smaller office branch. Planning the network architecture is vital because it either enhances or hinders the performance of the entire system. Choosing the wrong transmission media or equipment for a particular expected server load, for instance, can cause slowdowns on the network. Network architecture can also facilitate security, becoming increasingly important as more user devices connect to the network. The design and protocols of the network need to support quick and efficient user recognition and authorization. Most network architectures adopt the Open Systems Interconnection Model or OSI. This conceptual model separates the network tasks into seven logical layers, from lowest to highest abstraction. The Physical layer, for instance, deals with the wire and cable connections of the network. The highest layer, the Application layer, involves APIs that deal with application-specific functions like chat and file sharing. The OSI model makes it easier to troubleshoot the network by isolating problem areas from each other.

4. Network Architecture Services and APIs » Ethernet – datagram broadcast » IP – best-effort datagrams over internets » socket programming interface Protocols » IP, TCP, ARP, ICMP, DHCP, DNS, RIP, OSPF, BGP, . . . Algorithms/Mechanisms » OSPF, BGP, DNS name resolution » longest prefix matching, congestion control » packet classification, policy-based packet handling Applications » Telnet, FTP, WWW, overlay networks, . . . » not strictly part of architecture, but motivate and shape it Usage patterns, operational procedures » use of port numbers by applications » administration of addresses

5. Network Architecture Assumptions Driving assumptions often implicit » to understand architecture, need to make assumptions explicit » effectiveness can depend on validity of assumptions Technology assumptions » network bandwidth, processing capabilities of network elements » maintaining state in network elements is hard/expensive » wireless bandwidth is limited, wireless power is scarce Application assumptions » internet for accessing expensive computing resources » no one wants video conferencing Assumptions about user behavior » hosts locations don’t change » exponential packet length distributions adequately model reality » users will not abuse internet openness Poor assumptions can lead to poor design choices. Assumptions can become self-fulfilling prophecies. Validity of assumptions generally changes over time

6. Expecting the Unexpected Successful networks grow and last a long time » if objective is success, plan for “unreasonable” growth » easy to under-estimate network usage and longevity Technology capabilities change » can only predict with confidence for short term (say 10 years) » best not to let near-term constraints limit future developments » at same time, must be feasible in short term to succeed Networks get used in unexpected ways » Murphy’s Law for Networks – if users can do it, they will » unexpected uses can be positive (web) or negative (DoS) » can constrain non-standard uses (e.g. telephone network) or encourage them (e.g. internet) –even constrained nets get stretched (modems, fax , blue box) Aggregate behavior can emerge in strange ways » flash crowds, fractal traffic characteristics

7. Understanding Motivations Evolution of public networks depends on many stakeholders with variety of motivations Internet service providers » more customers and more “value-added” services » reduce costs (equipment, installation, support) Equipment vendors (both systems and components) » promote interest in new features » use technology to drive down cost (production & development) Application and higher level service providers » need network to reach users and deliver services » network services constrain applications and quality of delivery Policy makers » respond to constituents, lobbyists, technocrats Research community » fame and (occasionally) fortune Users and consumer organizations » avoiding growth in costs, ensuring broad access

8. Design Principles Can offer useful framework to guide design decisions » help maintain consistency as network evolves Example: protocol layering » each protocol layer should provide service through well-defined interface, while concealing implementation details » to facilitate correct implementation and enable change Example: end-to-end argument » network should provide only those services that cannot be provided effectively by endpoints » to minimize network complexity, avoid limiting applications Design principles can become controversial » admit variety of interpretations (QoS and end-to-end principle) » purists and pragmatists often dispute their sanctity Changing conditions can challenge their validity » are firewalls a blatant violation of e2e-ism, or an inevitable response to deficiencies in the internet architecture? Or both?

9. Elements of Effective Architectures Utility of provided services and supported applications » must be useful and must be used Minimal barriers to usage » easy for application developers to understand and use Scalability » in number of endpoints – how big is big enough? – N per person? what about tiny smart devices (smart dust)? » in geographic scope – local, national, global, galactic » performance of network elements (links, routers, end systems) Adaptability » make effective use of new technology as it develops » don’t limit architecture to constraints of current technology External factors often determine success » IP succeeded in spite of design flaws –BSD Unix, NSF-net and web were key drivers in its success » FDDI had significant technical advantages, but not enough to overcome Ethernet market dominance

10. Role of Geographic Distribution Whole point of networks is to connect remote endpoints Fundamental impact of distance » speed-of-light delays and impact on interactive applications –for both data and control » collision detection in CSMA/CD » power consumption of wireless links as function of distance Widely distributed networks have distributed control » equipment owned by individuals and organizations » typically means local and variable control » effective operation of the whole requires cooperation –advisable to minimize aspects that require cooperation between organizations – especially if organizations are competitors connectivity » constrained by technology, geography, organizational boundaries » impact on how traffic flows, how failures affect communication and who makes money

11. Modularity in Network Architectures “architecture...defines how system is broken into parts & how those parts interact.” – from NewArch Final Report Layered models used to describe network protocols » useful for defining services offered by layers, and reasoning about correctness » but, layer boundaries often violated for performance reasons » some functions (e.g. net management) necessarily span layers Modules and interfaces define implementation units » enable different organizations to implement different parts » allow for multiple versions of given parts Interfaces create opportunities for new functions » NAT depends on IP packet format, use of port numbers in UDP and TCP and prevalence of client-server interaction » firewalls depend on application usage of port numbers » usage patterns can lead to implicit interfaces

12. Network Architecture Design The design of any digital network architecture involves optimizing its building blocks. These include: Hardware These are the equipment that forms the components of a network, such as user devices (laptops, computers, mobile phones), routers, servers, and gateways. So, in a way, the goal of any network architecture is to find the most efficient way to get data from one hardware point to another.

13. Transmission Media Transmission media refers to the physical connections between the hardware devices on a network. Different media have various properties that determine how fast data travels from one point to another.They come in two forms: wired and wireless. Wired media involve physical cables for connection. Examples include coaxial and fiber optic. Wireless media, on the other hand, relies on microwave or radio signals. The most popular examples are WiFi and cellular.

14. Protocols Protocols are the rules and models that govern how data transfers between devices in a network. It’s also the common language that allows different machines in a network to communicate with each other. Without protocols, your iPhone couldn’t access a web page stored on a Linux server. There are many network protocols, depending on the nature of the data. Examples include the Transmission Control Protocol / Internet Protocol (TCP/IP) used by networks to connect to the Internet, the Ethernet protocol for connecting one computer to another, and the File Transfer Protocol for sending and receiving files to and from a server. Topology How the network is wired together is just as important as its parts. Optimizing this is the goal of network topology.Topology is the structure of the network. This is important because factors like distance between network devices will affect how fast data can reach its destination, impacting performance. There are various network topologies, each with strengths and weaknesses.

15. Ethernet Architecture Designed to connect computers in building or campus Technology-driven architecture » passive coaxial cable » asynchronous access, synchronous transmission » broadcast medium » access using CSMA/CD » 10 Mb/s transmission rate with Manchester encoding

16. Why are there different network architectures? Computer networks are built to serve the needs of their clients. Described below are three common types of enterprise networks: Access networks, for campuses and branches, are built to bring users and things onboard, such as connecting employees within an office building. Networks for data center connect servers that host data and applications and make them available to users. Wide-area networks (WANs) connect users to applications, sometimes over long distances, such as connecting hospital workers to health applications. These and all other networks face different security threats, which they need to guard against. To accommodate these varied requirements, all network types have unique architectures

17. Types of Architecture Peer-To-Peer network Client/Server network

18. Peer-To-Peer network Peer-To-Peer network is a network in which all the computers are linked together with equal privilege and responsibilities for processing the data. Peer-To-Peer network is useful for small environments, usually up to 10 computers. Peer-To-Peer network has no dedicated server. Special permissions are assigned to each computer for sharing the resources, but this can lead to a problem if the computer with the resource is down.

19. Advantages Of Peer-To-Peer Network: It is less costly as it does not contain any dedicated server. If one computer stops working but, other computers will not stop working. It is easy to set up and maintain as each computer manages itself. Disadvantages Of Peer-To-Peer Network: In the case of Peer-To-Peer network, it does not contain the centralized system . Therefore, it cannot back up the data as the data is different in different locations. It has a security issue as the device is managed itself.

20. Client/Server Network Client/Server network is a network model designed for the end users called clients, to access the resources such as songs, video, etc. from a central computer known as Server. The central controller is known as a server while all other computers in the network are called clients . A server performs all the major operations such as security and network management. A server is responsible for managing all the resources such as files, directories, printer, etc. All the clients communicate with each other through a server. For example, if client1 wants to send some data to client 2, then it first sends the request to the server for the permission. The server sends the response to the client 1 to initiate its communication with the client 2.

21. Advantages Of Client/Server network: A Client/Server network contains the centralized system. Therefore we can back up the data easily. A Client/Server network has a dedicated server that improves the overall performance of the whole system. Security is better in Client/Server network as a single server administers the shared resources. It also increases the speed of the sharing resources. Disadvantages Of Client/Server network: Client/Server network is expensive as it requires the server with large memory. A server has a Network Operating System(NOS) to provide the resources to the clients, but the cost of NOS is very high. It requires a dedicated network administrator to manage all the resources.