Question: What mechanism ensures forwards and backwards compatibility in the E-UTRAN X2 Application Protocol (X2AP), allowing for seamless decoding of messages across different standard versions?
Option 1: Dynamic Message Routing based on Standard Version
Option 2: Periodic Update of Decoding Schemas by Network Nodes
Option 3: Utilization of Variable Length Subnet Masks (VLSM)
Option 4: Inclusion of ID and Criticality Fields in a Standard Format for Messages, IEs, or Groups of Related IEs
Explanation: The inclusion of ID and criticality fields in a standard, unchanging format within messages, Information Elements (IEs), or groups of related IEs ensures consistent decoding. This approach guarantees forwards and backwards compatibility, allowing newer and older protocol versions to understand the basic message structure, maintaining interoperability during network upgrades or interactions between differently versioned nodes.