scope:

An ITU-T H.248 media gateway (MG) may provide ITU-T H.248 IP-to-IP contexts, which implies an IP forwarding function (in the ITU-T H.248 bearer path or IP data path). There are many different forwarding functions possible, dependent on the set of packet processing functions executed, and dependent on whether the MG behaves as a host or a hop system. Two basic forwarding functions may be identified:

- Back-to-back IP host (B2BIH) mode.

- IP router (IPR) mode.

The B2BIH mode is inherently supported by the ITU-T H.248.1 protocol architecture; the IPR mode is addressed within this Recommendation. In the IPR mode, if IP packets are routed between a private network and a public network, network address translation (NAT) functionality is also supported by this Recommendation.