Published on February 19, 2014
Internet Architecture and Protocols University of education township campus lahore, Pakistan Lecture 02 Introduction of Internet, Building Blocks Internet Architecture and Protocols, University of education township campus lahore, Pakistan 1
Introduction Computer Network: “An interconnected collection of autonomous/independent computers that are capable of exchanging information” Two computers are said to be interconnected if they are able to exchange information The most elementary network consists of two computers communicating over a cable The old model of a single computer serving all of the organization’s computational needs has now been replaced by one in which a large number of separate but interconnected computers do the job. These systems are called computer networks. 2
Introduction Uses of computer networks Computer Networks are everywhere ↗ ↗ ↗ ↗ ↗ ↗ ↗ ↗ ↗ ↗ Email World Wide Web, Video Conferencing File Transfer Collaborative Virtual Environments Remote control of robots and machines Distributed Programs and Applications Hacking Banking Internet telephone . . . . . . . . . . etc 3
Introduction Why Do We Need Computer Networks We need computer networks for ↗Sharing of resources ↗Sharing of data ↗Sharing of ideas So, a computer network Eliminates the geographical constraints, improve communications and more than one person can work on a single job. 4
Components of a Computer Network 5
Classification of Computer Networks Computer networks are classified by many factors: 6
Roles of a computer in a Network ↗ Server: They provide network resources ↗ Client: They use but not provide network resources ↗ Peer: They both use and provide network resources 7
Network Architectures ↗ Server based Networks ↗ Peer Networks ↗ Hybrid Networks 8
Network Architectures Server based Networks ↗Server based networks are defined by the presence of servers on the network and are responsible for security and administration ↗All the resources are with server ↗Clients request services, such as file storage and printing and servers deliver them ↗Server computers typically are more powerful than client computers 9
Network Architectures Advantages: ↗ ↗ ↗ ↗ ↗ ↗ ↗ ↗ Security Centralized control Central file storage Central backup Ability to pool available resources Share expensive equipment Optimized faster dedicated servers Easy manageability Disadvantages: ↗ Expensive dedicated hardware ↗ Network OS and software are expensive ↗ Network administration required Pooling is a resource management term that refers to the grouping together of resources (assets, equipment, personnel, effort, etc.) for the purposes of maximizing advantage and/or minimizing risk to the users. The term is used in many disciplines. 10
Network Architectures Peer networks ↗Peer networks are defined by the lack of central control over the network ↗There are no servers in peer networks ↗Peer networks are organized into workgroups ↗These are used for small networks 11
Network Architectures Advantages: ↗ ↗ ↗ ↗ No extra investment in hardware and software Easy setup, Low cost No network administrator required Ability of user to control sharing Disadvantages: ↗ ↗ ↗ ↗ ↗ Additional loads on computer because of resource sharing Lack of central organization No central point for file storage Weak and intrusive security Each user must administrate its own computer 12
Network Architectures Hybrid networks ↗Hybrid networks have all three types of computers operating on them and generally have active domains and workgroups ↗This means that while most shared resources are located on servers, network users still have access to any resources being shared by peers in the workgroup Advantages : ↗The advantages of server based networking as well as of peer based networking ↗Ability of users and network administrator to control security based on the importance of the shared resource Disadvantages : ↗They share the disadvantages of server based as well as peer based networking 13
Two Basic Network Structures Workgroups vs Domains 14
Two Basic Network Structures ↗ A domain is a logical grouping of networked computers that share a centralized database which contains user accounts and security information for the domain ↗ A domain is a specific name given to a LAN that includes one or more Servers (Domain Controllers) ↗ Advantage, you have a dedicated server to log/track all users and shares via Active Directory, disadvantage is the cost and maintenance required to keep this configuration running ↗ A workgroup is a logical grouping of networked computers that share resources ↗ A workgroup has not dedicated server(s) to track users and such, it's all done via each client machine on the LAN, this includes shared objects and user logons ↗ Advantage, cheaper to run and maintain as you only need two machines running in the same workgroup to be called a workgroup , disadvantage no centralize management and security 15
Network Building Blocks A network can be defined/build recursively as: ↗Two or more nodes connected by a link ↗When we have more than two nodes, we need intermediate devices to connect them ↗Circular nodes (switches) implement the network Squared nodes (hosts) use the network 16
Network Building Blocks ↗ Two or more networks connected by one or more nodes; internetworks ↗ Circular nodes (router or gateway) interconnects the networks A cloud denotes “any type of independent network” 17
Network Building Blocks 18
Network Building Blocks Nodes ↗Hosts: general-purpose computers ↗Switches: typically special-purpose hardware ↗Routers : connecting networks Links ↗Copper wire with electronic signaling ↗Glass fiber with optical signaling ↗Wireless with electromagnetic (radio, infrared, microwave) signaling 19
Network Building Blocks Switching Strategies Circuit switching: ↗carry bit streams ↗establishes a dedicated circuit ↗links reserved for use by communication channel ↗send/receive bit stream at constant rate ↗example: original telephone network Packet switching: ↗store-and-forward messages ↗operates on discrete blocks of data ↗utilizes resources dynamically according to traffic demand ↗send/receive messages at variable rate ↗example: Internet 20
Network Building Blocks Hosts are directly or indirectly connected to each other 21
Network Building Blocks Address: byte-string that identifies a node ↗ Usually unique Routing: forwarding decisions ↗ Process of determining how to forward messages to the destination node based on its address Types of addresses ↗ unicast: node-specific ↗ broadcast: all nodes on a network ↗ multicast: some subset of nodes on a network 22
Network Building Blocks ↗ A network can be constructed from nesting of networks ↗ An address is required for each node that is reachable on the network ↗ Address is used to route messages toward appropriate destination Enough ??? ↗ A network is delivering packets among a collection of computers ↗ How application processes communicate in a meaningful way? ↗ Hide network complexity by implementing the common services 23
Network Building Blocks ↗ Turn host-to-host connectivity into process-to-process communication, making the communication meaningful Host Host Application Host Application Channel Host Host 24
Network Building Blocks 25
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