1 / 17

Classes of Networks

Classes of Networks. LAN (Local Area Network) Maximum distance not more than a few kms Ownership by a single organization Transmission speed of at least several Mbps (tens to hundreds are economical) Often broadcast, shared media based. Classes of Networks - LANS.

ariana-campbell
Download Presentation

Classes of Networks

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Classes of Networks • LAN (Local Area Network) • Maximum distance not more than a few kms • Ownership by a single organization • Transmission speed of at least several Mbps (tens to hundreds are economical) • Often broadcast, shared media based

  2. Classes of Networks - LANS • Some widely used standards include: • IEEE 803.3 - Ethernet • IEEE 803.5 - Token ring • FDDI • ATM • An important issue in broadcast LANs is the allocation of the shared channel (media access control) • Control may be static (time division multiplexing) or dynamic (contention or arbitration)

  3. Classes of Networks - MANS • MAN (Metropolitan Area Network) • Distances between 5 and 50 kms • Data rate above 1 Mbps • Standards: IEEE 802.6 DQDB, FDDI, and ATM

  4. Classes of Networks - WANS • WAN (Wide Area Network) • Spans entire states or countries • Data rate of 1.544 (T1), and 45 (T3) Mbps common • Higher data rates are available with the wide deployment of ATM backbone networks • Often owned by multiple organizations

  5. Classes of Networks - WANS • Usually separate communications functions from application functions • Transmission lines: circuits, channels or trunks • Switching elements: • Specialized computers connecting two or more circuits • These elements receive data on an incoming circuit and transmit it on an outgoing circuit

  6. Classes of Networks - WANS • Intermediate Systems, Packet SwitchingNode, Data Switching Exchange, Router, etc. • Intermediate systems store a complete packet before forwarding it • store-and-forward; packet switched; point-to-point network

  7. Classes of Networks - Internetworks • Internetworks • Unlike WANs they often interconnect different, incompatible networks • Use special types of intermediate systems called Gateways • Gateways translate between different types of physical media and network software

  8. Network Software • Network software is highlystructured • This technique has been immensely successful • The key is Layered design • Each layer provides a service to the layer above • Each layer hides details of how the service is provided to the layer above • The Nth layer on one machine “talks to” or interacts with the Nth layer on another machine

  9. Network Software - Protocols • Conventions and rules governing this interaction are specified by the Layer N Protocol • A protocol is an agreement about how communications are to proceed • Without a protocol, communication can be difficult or even impossible • E.g. Telephone conversation, Postal addresses

  10. Layer 5 Protocol Layer 5 Layer 5 Layer 4 Layer 4 Protocol Layer 4 Layer 3 Layer 3 Protocol Layer 3 Layer 2 Layer 2 Protocol Layer 2 Layer 1 Layer 1 Protocol Layer 1 Network Software - Protocols Peer “entities” Interface Interface Interface Interface Physical Medium

  11. Network Software - Protocols • Information is not actually transferred directly between peer layer N entities • Peer layer N entities carry on a virtual communication using the services of the layers below • Layer N passes data and control information down to (or receives data and control from) Layer N-1 until the physical medium is reached

  12. Network Software - Interfaces & Services • Interfaces exist between each layer • Interface defines which primitive functions and services layer N-1 provides to layer N • Want layers to: • Perform a well defined, logically related set of functions • Minimize the amount of information needed to pass between layers • Keep interfaces “clean” to allow easy and transparent replacement of layers

  13. Network Software - Protocols • The set of protocols and layers together make up the Network Architecture • A Network Architecture Specification must provide enough information to allow implementation in hardware/software • Implementation specific details are not part of the architecture and should be irrelevant for inter-operation • With one protocol per layer we have a Protocol Stack

  14. The benefits of Layered Protocols • Network Architectures, Protocols and Protocol stacks are the Fundamentals of Computer Networks • They form the foundation for the very considerable success of computer networks in the real world • Multilayer communications protocols allow • ready adaptation of successful protocols to new technology (prevent obsolescence) • migration of protocols from software implementation (slow) to hardware (fast) as they evolve

  15. More Benefits of Layered Protocols • Separate data and control information • Support differing levels of abstraction (message, packet, frame) with different sizes • Allow segmentation of large messages • Peer process abstraction facilitates reduction of difficult design task (a network architecture) into smaller manageable tasks (protocol layer architecture) • Typically lower layer protocols of “network software” are implemented in silicon (hardware)

  16. Understanding Services and Protocols • Protocol is set of rules about the format and meaning of data units exchanged by peers • Protocol is used by entities to implement services • Protocol and/or its implementation can change and as long as the Service (interface) remains unchanged, higher layers are happy and continue to work • Like in abstract data types or object orientation, we decouple interface and implementation

  17. Layering concept elsewhere • Layering is used in other software (e.g. Operating systems) - UNIX • For Network Software the important difference is that we are not allowed to violate layering (Layer 5 cannot directly access Layer 1) • For Network Software, its important Layers don’t “peek” into headers of other layers and rely on protocol data of other layers

More Related