PRODUCT_LINE: BCM
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Patch: BCM 3.7 Paging Performance Enhancement

Applicable Platform: BCM 3.7

Recommendation: Non-critical

Component and Version: IPTelephony

Dependencies: None

The following issues are addressed:
o Q01232995: BCM 400 3.7, MVC paging problems
o Q01103150: BCM 3.6 IP Sets No Speech Path after CP 2.0 Patch Applied

The enabling of the Unidirectional Paths feature in the Media Path Server has resulted in no speech path issues with IP sets. It appears that some customers are deploying IP sets behind third-party NAT devices such as Linksys WRT54G, even though this is not an officially supported configuration. The unidirectional streams feature breaks compatibility with a specific type of NAT devices commonly called "port restricting" NATs. Such devices filter packets flowing from public into private domains and only allow packets form Y:y IP-address:port combination into the private domain destined to X:x internal address if it has seen recently (within 60 sec) at least one packet flowing from X:x to Y:y. Such a packet is said to create a pinhole in the NAT.
With bidirectional streams whenever an incoming IP set stream is setup by UTPS, the corresponding outgoing RTP stream is always set up by the UTPS on request from MPS. Both streams have matching ip addressing info. So, the first packet on outgoing stream generates a pinhole in the NAT. With the introduction of unidirectional streams this is no longer a case, so whenever a unidirectional stream is setup the NAT filters the packets out in multiple scenarios. One such case is a case of a set going off hook. A unidirectional stream is open to produce dial tone from BCM. The NAT does not let the dial tine through. IN the case on an outgoing call the ring back tones are also delivered via unidirectional streams. There are perhaps other examples of such issues with background music and music on hold that have not been seen in the field, but should exhibit similar behavior.