1 / 12

Emerged Technologies X.25

Emerged Technologies X.25. Nirmala Shenoy Department of Information Technology Rochester Institute of Technology. X.25. Scope Purpose Typical topology Layers PDU Any other aspects Conclusion. X.25. Purpose User interface specification for packet switched networks

telma
Download Presentation

Emerged Technologies X.25

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. Emerged Technologies X.25 Nirmala Shenoy Department of Information Technology Rochester Institute of Technology

  2. X.25 • Scope • Purpose • Typical topology • Layers • PDU • Any other aspects • Conclusion

  3. X.25 • Purpose • User interface specification for packet switched networks • Packet switched networks • Public • Any configuration • Any protocol

  4. X.25 • Purpose • Specification of data exchange between user device (DTE) and network (DCE) • DCE is the agent used by the DTE to access the packet switched network • Expected data flow over unreliable media • Flow control

  5. X.25 • Purpose • Expected data flow over unreliable media • Error control on payload • Sequence numbers • Acks • QoS control • X.75 proposed NNI protocol

  6. X.25 • Three Layers of X.25 • Physical layer • V series, X.21, X.21bis etc • Data Link Layer – LAPB • Link Access protocol Balanced • Subset of HDLC • Network Layer – PLP • Packet Layer Procedures

  7. X.25 • PDUs in X.25 - PLP • PLP creates the packets that are to be transferred – end-to-end • Establish a connection • Tear down a connection • Manage packet flow • Uses sequence numbers, acks etc • Logical channel number management

  8. X.25 • PDUs in X.25 – LAPB • Payload of LAPB is PLP packet • PLP packet is in the information field • Address fields • Checksum • Link ctrl • Ack, Naks, Redundancy in reliability control

  9. X.25 • Other Aspects • PLP can support 4095 logical channels • Allocates and maintains the LCNs • Logical Channel Number • Virtual circuit comprise 2 logical channels at both ends

  10. X.25 • Other Aspects - Virtual circuits in X.25 • PVCs • Agreed by end users and network • SVCs • Based on need • Call request, Call tear down procedures

  11. X.25 • Other features • Provision for user requested QoS control • Special services • Call redirection • Closed user groups • Reverse charge

  12. X.25 • Conclusions • Intended to support an error prone WAN configuration • Old physical interfaces used • Pioneered the concepts of PVCs, SVCs, VCIs

More Related