Navigating the landscape of roaming relations in the era of 5G requires a nuanced understanding of trust dynamics among the various entities involved. In a simplified world of direct roaming relations, only mobile operators are trusted endpoints for any communication related to roaming. This established trust is the cornerstone upon which the integrity of roaming exchanges is built. 
 
However, the operational reality extends beyond this direct exchange, with intermediary entities that carry significant implications for security discussions. Paradoxically, these intermediaries, such as IPX carriers, are often seen as more trustworthy than the actual roaming partners, as they provide a wide range of value-added services to assist mobile operators in simplifying the complexities of roaming business operations. These services operate with strict confidentiality and are meticulously managed via dedicated IPX access lines, which remain completely isolated from external access.  
 
IN 5G, TLS connections provide additional security by encrypting control plane traffic, safeguarding against potential breaches of points-of-interconnect or brute-force access to physical data links.

Consider this: The TLS protocol, in existence since 1999, has played a pivotal role in ensuring secure communication.

It’s the very technology that secures HTTPS connections, making our web browsing experience safe. Therefore, it stands as a well-known, well-established protocol.  

The TLS hop-by-hop philosophy acknowledges this reality and introduces trusted parties on the route from the visited mobile network to the home mobile network and vice versa. These trusted parties will act as credential holders, serving as valid endpoints of control plane connection. This role is indicated by the N32 interface reference point defined by the GSMA’s 3GPP standards.

This enables a straightforward 5G SA roaming setup, similar to what we’ve seen in previous mobile generations. However, it doesn’t prevent mobile network operators from directly connecting using N32 connections if they choose to do so.

TLS hop-by-hop doesn’t undermine the fundamental trust model between the User Equipment (UE) and the operator. Instead, it establishes a built-in hierarchy of trust on the control plane. In this hierarchy, the next hop is considered more trustworthy than any other party in the communication chain.