This specification defines a new SDP Grouping Framework extension, 'BUNDLE'. The extension can be used with the Session Description Protocol (SDP) Offer/Answer mechanism to negotiate the usage of a single 5-tuple for sending and receiving media associated with multiple SDP media descriptions ("m="). This is referred to as bundled media. This specification also defines a new SDP attribute, 'bundle-only', which can be used to request that specific media is only used if bundled. This specification also updates sections 5.1, 8.1 and 8.2 of RFC 3264. The update allows an answerer to assign a non-zero port value to an "m=" line in an SDP answer, even if the "m=" line in the associated SDP offer contained a zero port value.