Port 753

Reverse Routing Header (RRH) is a network protocol primarily aimed at experimental or specialized routing scenarios. It enables the inclusion of routing instructions in packet headers, specifying how packets should be routed across complex network topologies. This functionality was conceived to give source devices or intermediate routers better control over traffic flows, particularly in multipath routing or specific route reversal processes.

The RRH protocol operates mainly over TCP on port 753, utilizing its reliable transport characteristics to ensure the correct transmission of routing control information. The protocol allows the sender to embed routing directives, which are used by intermediate devices to manage packet forwarding decisions dynamically. Because of its niche purpose, RRH is not widely adopted in mainstream networks but might be encountered in experimental IP routing environments, research networks, or certain specialized implementations.

RRH is part of a family of IP routing header extensions aiming to increase routing flexibility. While its intended to enhance control over routing paths, modern networks typically favor other mechanisms such as MPLS, SDN controllers, or overlay networks for similar functionality. Consequently, RRH remains largely an experimental technology without broad deployment.