ну хотя бы ради этого
If a request is within 200 bytes of the path MTU, or if it is larger
than 1300 bytes and the path MTU is unknown, the request MUST be sent
using an RFC 2914 [43] congestion controlled transport protocol, such
as TCP.
https://datatracker.ietf.org/doc/html/rfc3261#section-18.1.1
вам хоть раз не хватало
notify c гигантскими данными ?

