B.1 The need for security protection

33.2103GPPIP network layer securityNetwork Domain Security (NDS)Release 17TS

The GPRS Tunnelling Protocol (GTP) is defined in 3GPP TS 29.060 [6]. The GTP protocol includes both the GTP control plane signalling (GTP-C) and user plane data transfer (GTP-U) procedures. GTP is defined for Gn interface, i.e. the interface between GSNs within a PLMN, and for the Gp interface between GSNs in different PLMNs.

GTP-C is used for traffic that that is sensitive in various ways including traffic that is:

– critical with respect to both the internal integrity and consistency of the network;

– essential in order to provide the user with the required services;

– crucial in order to protect the user data in the access network and that might compromise the security of the user data should it be revealed.

Amongst the data that clearly can be considered sensitive are the mobility management messages, the authentication data and MM context data. Therefore, it is necessary to apply security protection to GTP signalling messages (GTP-C).

Network domain security is not intended to cover protection of user plane data and hence GTP-U is not protected by NDS/IP mechanisms.

Table 1 presents a list of GTP interfaces that shall be considered by NDS/IP.

Table 1: GTP Interfaces that are affected by NDS/IP

Interface	Description	Affected protocol
Gn	Interface between GSNs within the same network	GTP
Gp	Interface between GSNs in different PLMNs.	GTP