IPv4 Service Continuity Prefix
Dual-Stack Lite (DS-Lite), defined in RFC 6333, directs IANA to reserve 192.0.0.0/29 for the Basic Bridging BroadBand (B4) element. Per this memo, IANA has generalized that reservation to include other cases where a non-routed IPv4 interface must be numbered as part of an IPv6 transition solution.