The following material from the book "Data Networks," (2nd edition) Prentice Hall, , ISBN , may be freely downloaded and used freely for any. DATA. NETWORKS. Dimitri Bertsekas. Massachusetts Institute of Technology . The field of data networks has evolved over the last fifteen years from a stage. Data Networks, IP and the Internet. Protocols, Design and Operation. Martin P. Clark. Telecommunications Consultant, Germany.

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This tutorial is prepared for the beginners to help them understand Data. Communication and Computer Networks. Prerequisites. Before proceeding with this. PDF | Telecommunication systems are communication systems at a distance by technological means, particularly via electrical signals or. Introduction. -A network can be defined as a group of computers and other devices connected in some ways so as to be able to exchange data. -Each of the .

Connectionless and connection-oriented modes[ edit ] Packet switching may be classified into connectionless packet switching, also known as datagram switching, and connection-oriented packet switching, also known as virtual circuit switching. Connection-oriented systems include X. In connectionless mode each packet is labeled with a destination address, source address, and port numbers.

It may also be labeled with the sequence number of the packet. This information eliminates the need for a pre-established path to help the packet find its way to its destination, but means that more information is needed in the packet header, which is therefore larger. The packets are routed individually, sometimes taking different paths resulting in out-of-order delivery.

At the destination, the original message may be reassembled in the correct order, based on the packet sequence numbers. Thus a virtual circuit carrying a byte stream is provided to the application by a transport layer protocol, although the network only provides a connectionless network layer service. Connection-oriented transmission requires a setup phase to establish the parameters of communication before any packet is transferred.

The signaling protocols used for setup allow the application to specify its requirements and discover link parameters. Acceptable values for service parameters may be negotiated. The packets transferred may include a connection identifier rather than address information and the packet header can be smaller, as it only needs to contain this code and any information, such as length, timestamp, or sequence number, which is different for different packets.

In this case, address information is only transferred to each node during the connection setup phase, when the route to the destination is discovered and an entry is added to the switching table in each network node through which the connection passes.

When a connection identifier is used, routing a packet requires the node to look up the connection identifier in a table. Connection-oriented transport layer protocols such as TCP provide a connection-oriented service by using an underlying connectionless network. In this case, the end-to-end principle dictates that the end nodes, not the network itself, are responsible for the connection-oriented behavior. Packet switching in networks[ edit ] Packet switching is used to optimize the use of the channel capacity available in digital telecommunication networks, such as computer networks, and minimize the transmission latency the time it takes for data to pass across the network , and to increase robustness of communication.

The best-known use of packet switching is the Internet and most local area networks.

For example, Ethernet and Frame Relay are common. Newer mobile phone technologies e. These virtual circuits carry variable-length packets. In , X.

Asynchronous Transfer Mode ATM also is a virtual circuit technology, which uses fixed-length cell relay connection oriented packet switching.

Datagram packet switching is also called connectionless networking because no connections are established. Virtual circuits are especially useful in building robust failover mechanisms and allocating bandwidth for delay-sensitive applications.

Frame Relay[ edit ] Both X. Another major difference between X. Frame Relay does not define any such handshakes. It only operates at the user-network-interface UNI. Thus, the network provider is free to use any procedure it wishes inside the network.

As such, its integrity operations pertain only between nodes on a link, not end-to-end. Any retransmissions must be carried out by higher layer protocols. The X. It was widely used at the UNI for packet switching networks during the s and early s, to provide a standardized interface into and out of packet networks.

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Some implementations used X. Thus, it rids itself of many X. The simplicity of Frame Relay makes it faster and more efficient than X. Because Frame Relay is a data link layer protocol, like X.

For X. How this is done is up to the network provider. However, X. Before the introduction of X.

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Two fundamental differences involved the division of functions and tasks between the hosts at the edge of the network and the network core. In the datagram system, the hosts have the responsibility to ensure orderly delivery of packets.

Packet switching

In the virtual call system, the network guarantees sequenced delivery of data to the host. This results in a simpler host interface with less functionality than in the datagram model.

AppleTalk[ edit ] AppleTalk is a proprietary suite of networking protocols developed by Apple in for Apple Macintosh computers. It was the primary protocol used by Apple devices through the s and s.

AppleTalk included features that allowed local area networks to be established ad hoc without the requirement for a centralized router or server. The AppleTalk system automatically assigned addresses, updated the distributed namespace, and configured any required inter-network routing. It was a plug-n-play system. AppleTalk support was available in most networked printers, especially laser printers , some file servers and routers.

It initially had only one host but was designed to support many hosts. Users that are allowed access to data in these servers do not need to identify themselves, but instead log in as an anonymous guest. A subnet mask is combined with an IP address in order to identify two parts: the extended network address and the host address.

Like an IP address, a subnet mask is made up of 32 bits. A single segment of UTP cable has an allowable length of 90 to meters.


This limitation can be overcome by using repeaters and switches. Data encapsulation is the process of breaking down information into smaller manageable chunks before it is transmitted across the network.

It is also in this process that the source and destination addresses are attached into the headers, along with parity checks. It shows how devices and cables are physically laid out, as well as how they connect to one another.

VPN means Virtual Private Network, a technology that allows a secure tunnel to be created across a network such as the Internet. For example, VPNs allow you to establish a secure dial-up connection to a remote server. This is a protocol that provides a way for multiple computers on a common network to share single connection to the Internet. The Network layer is responsible for data routing, packet switching and control of network congestion.

Routers operate under this layer. Network topology dictates what media you must use to interconnect devices. It also serves as basis on what materials, connector and terminations that is applicable for the setup. RIP, short for Routing Information Protocol is used by routers to send data from one network to another.

It efficiently manages routing data by broadcasting its routing table to all other routers within the network. It determines the network distance in units of hops. There are several ways to do this. Install reliable and updated anti-virus program on all computers.

Make sure firewalls are setup and configured properly. User authentication will also help a lot. All of these combined would make a highly secured network. This is a peripheral card that is attached to a PC in order to connect to a network. It is an interconnection of computers and devices that are geographically dispersed. It connects networks that are located in different regions and countries. The physical layer does the conversion from data bits to electrical signal, and vice versa.

This is where network devices and cable types are considered and setup. Proxy servers primarily prevent external users who identifying the IP addresses of an internal network.

Without knowledge of the correct IP address, even the physical location of the network cannot be identified. Proxy servers can make a network virtually invisible to external users.

This layer provides the protocols and means for two devices on the network to communicate with each other by holding a session. This includes setting up the session, managing information exchange during the session, and tear-down process upon termination of the session. Are there limitations? A fault tolerance system ensures continuous data availability. This is done by eliminating a single point of failure.

However, this type of system would not be able to protect data in some cases, such as in accidental deletions.

The 10 refers to the data transfer rate, in this case is 10Mbps. The word Base refers to base band, as oppose to broad band. T means twisted pair, which is the cable used for that network. Private IP addresses are assigned for use on intranets.

These addresses are used for internal networks and are not routable on external public networks. These ensures that no conflicts are present among internal networks while at the same time the same range of private IP addresses are reusable for multiple intranets since they do not "see" each other.

NOS, or Network Operating System, is specialized software whose main task is to provide network connectivity to a computer in order for it to be able to communicate with other computers and connected devices. DoS, or Denial-of-Service attack, is an attempt to prevent users from being able to access the internet or any other network services.

Such attacks may come in different forms and are done by a group of perpetuators. One common method of doing this is to overload the system server so it cannot anymore process legitimate traffic and will be forced to reset. It is made up of 7 layers, with each layer defining a particular aspect on how network devices connect and communicate with one another.

One layer may deal with the physical media used, while another layer dictates how data is actually transmitted across the network. The main purpose of this is to prevent crosstalk. Crosstalks are electromagnetic interferences or noise that can affect data being transmitted across cables. By using address translation instead of routing, address sharing provides an inherent security benefit. That's because host PCs on the Internet can only see the public IP address of the external interface on the computer that provides address translation and not the private IP addresses on the internal network.The private networks were often connected via gateways to the public network to reach locations not on the private network.

An IBM customer could acquire hardware and software from IBM and lease private lines from a common carrier to construct a private network.

NAT accelerates the routing process because no modifications are made on the packets. The presentation layer can be presented with data if all flows occur in some cases. It attempts to boot from a TFTP server. Therefore, no static address mapping is required.

An IP address must be configured for the port.

Only one process number can be used on the same router.