Introduction Origin and Design Assumptions
Designed as Access/Signaling Protocol
X.25 Stacks
PtP or NBMA
X.25 Addressing Persistent Addressing X.121 Extensions and Manipulations X.25 Transient/Channel Addressing Frame Level (LAP-B) Protocol Operation
Connection Establishment
User Information Transfer
Disconnection
Basic Interface Configuration
Tuning and LAPB Parameters Modulo and Window Size (K Parameter) N1 Parameter: Number of Bits per Frame N2 Parameter: Transmit Failures before Declaring Link Down T1 Timer: Retransmission Delay LAPB Interface Outage T4 timer: Unsignaled Link Failure X.25 Packet Layer Protocol Operation
Connection Establishment The Strange Case of Fast Select
Information Transfer The Difference between Frame and Packet Flow Control Fragmentation Mechanism Contemporary Fragmentation Application
Disconnection
Global Decisions in Configuring the Packet Layer Tuning with LCN Values
Interface-level Configuration Decisions - Basic Parameters Encapsulation Independence of DTE/DCE Status by Level X.25 Address X.25 Map
X.25 Packet Layer Protocol Parameters Window and Packet Size RFC 1356 advises: Protocol Timers Higher-Layer Protocol Family Mapping to X.25 Pros and Cons: Single or Multiple Protocols per VC Multiplexing versus Multiple Virtual Circuits
Higher Layer Address Mapping to X.121 X.25 Switching and Tunneling
X.25 Routes Position Selection Options Modification-Options Disposition Options
XOT Tunneling Connecting to X.25 PDNs
Closed User Groups Preferential CUGs and Actions on Incoming Calls Associated Protocols
PAD
X.75 The Lovely and Sneaky nvc Parameter Conclusion