Question: When introducing new functions in GTPv1-U to ensure backwards compatibility with Pre-Rel-8 nodes, how must new Information Elements be encoded?
Option 1: TLV-encoded and mandatory
Option 2: Fixed-length encoded and optional
Option 3: TLV-encoded and optional
Option 4: Variable-length encoded and mandatory
Explanation: To maintain backwards compatibility with older nodes, new elements must be designed to be gracefully ignorable. TLV encoding allows older nodes to skip over unknown elements based on the length field. Marking them as optional ensures communication with legacy nodes is not disrupted, thus ensuring full backwards compatibility.