DCN_rpj21

DCN_rpj21 - NT503: Data Communication & Networking X.25...

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
1 X.25 Frame Relay ISDN
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 X.25 ± Standard developed by CCITT (Consultative Committee for International Telegraphy and Telephony) ± Defines three layers, ¾ Physical ¾ Link ¾ Packet ± Physical layer protocol used is X.21 or V.24, which specifies electrical and procedural interface between the host and the network. ± Supports speed up to 64 Kbps, which are very low for many applications ± It is connection-oriented & supports Virtual Circuits (switched and permanent VC’s)
Background image of page 2
3 X.25 ± It’s an interface between attached host and packet switched network. ¾ X.21 allows analogue interface with switched network ¾ V.24 for analog interface for leased lines to switched network
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
4 X.25 Layers LAPB: Link Access Protocol Balanced (for Channel B, ISDN) PLP : Packet Layer Protocol http://www.inetdaemon.com/tutorials/telecom/x25/plp.html
Background image of page 4
5 X.25 Layers ± Link Layer: ¾ Reliable transfer across physical link by transmitting sequence of frames ¾ Error detection and control ¾ Synchronisation ¾ Link Access Protocol Balanced (for channel B, ISDN) ± Packet Layer: ¾ External virtual circuits, internal packet switching ¾ Logical connections (virtual circuits) between subscribers ¾ Supports permanent as well as switched VC’s
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
6 X.25 traffic
Background image of page 6
7 Frame Relay
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
8 Frame relay ± Frame relay is a connection-oriented, high speed, packet switched data communication service based on older X.25 technology ± Data rates up to 1.544 Mbps (uses T-1 link at present) and planned for T-3 link (44 Mbps in future) ± No ACK and error checking mechanism is provided for frames, resulting in higher data rates at lower costs ± ± It handles “bursty” data traffic more effectively than X.25 ± Frames can vary in size, but maximum 4,096 bytes
Background image of page 8