The DRA is between e.g. MME and HSS or SGSN and HSS and maybe between HSS and IMS S-CSCF/I-CSCF. In the IETF Spec RFC3588 you can read the following: IETF - RFC3588
The Hop-by-Hop Identifier is an unsigned 32-bit integer field (in network byte order) and aids in matching requests and replies. The sender MUST ensure that the Hop-by-Hop identifier in a request is unique on a given connection at any given time, and MAY attempt to ensure that the number is unique across reboots. The sender of an Answer message MUST ensure that the Hop-by-Hop Identifier field contains the same value that was found in the corresponding request. The Hop-by-Hop identifier is normally a monotonically increasing number, whose start value was randomly generated. An answer message that is received with an unknown Hop-by-Hop Identifier MUST be discarded.
--> for me it sounds like that the HbHid must not jump in numbers but rather increase step by step sequential – is that also your experience?
Issue: I wonder if that Hop-by-Hop Identifier really increases the number sequentially as it seems to be a similar Parameter like the Local Reference in SS7 (DLR, SLR). I do not recall that in SS7 the Source/Destination Local Reference Numbers have to be increased sequentially.
If the Hop-by-Hop ID jumps too much, the other side may not be able to follow and Signalling errors occur? Have you seen problems on HSS or MME when that Hop-by-Hop Identifier increases in big steps rather than sequential?