4.1.3 Inbound transit traffic

29.2043GPPArchitecture, functional description and protocol detailsRelease 17Signalling System No. 7 (SS7) security gatewayTS

This scenario is shown in figure 4.1.3. The message is originated at a NE outside the transit PLMN. It may transit several transit nodes outside the transit PLMN before it reaches the SS7 Security Gateway in inbound direction. This SS7 Security Gateway passes the message unmodified. The message may then transit several transit nodes inside the transit PLMN, another SS7 Security Gateway of the transit PLMN in outbound direction (see Clause 4.1.4), and several transit nodes outside the transit and destination PLMN (potentially including an SS7 Security Gateway) before it reaches the destination PLMN.

Note: A PLMN operator may decide not to act as transit network for specific or all combinations of origin and destination. In this case the SS7 Security Gateway may block the inbound message.

Figure 4.1.3: Inbound transit traffic