Patent Application
20080247386
This invention relates generally to network communications.
Real time fax relay, for example, implemented with a T.30 protocol, allows a local facsimile machine to send fax pages over one or more networks to a remote facsimile machine, such that the remote facsimile machine receives the fax pages while the local facsimile machine is still transmitting the fax pages. Due to real time nature of these fax transmissions, the T.30 protocol includes timeout functionality that allows the local facsimile machine to retransmit data from a fax page that was incorrectly received by the remote facsimile machine.
When there is excessive transmission delay over the communication network, the remote facsimile machine will trigger timeouts requesting the local facsimile machine retransmit the delayed data. This transmission delay may be caused when at least one of the networks are bandwidth constrained, or by other inherent properties of the networks. For instance, when one of the networks is an IP network, the total transmission delay increases with demodulation, packetization, and remodulation of fax data as well as the addition of de-jitter buffers. Previously, IP gateways spoofed the local facsimile machine into a “hold off” condition, forcing a postponement of the retransmission of fax data until the transmission delay lessened.
Fax pages are often transmitted through multiple tandemly coupled communication networks, such as a TDM network coupled between IP networks, requiring a conversion from packet encoding to an analog signal that adds to the total transmission delay. The transmission delay due to network conversion further increases with each additional tandemly coupled network. Since the transmission delay due to network conversion is systemically-based according to network configuration, many IP gateways will spoof or “hold off” retransmissions indefinitely thus locking up real time fax relay.
In network communications, an example system implementing fax relay tunneling includes a first network gateway coupled to a circuit-switched network, the first network gateway to initiate a tunnel through the circuit-switched network responsive to packetized fax relay data received from a packet-switched network, and a second network gateway couple to the circuit-switched network, the second network gateway to receive packetized fax relay data through a tunnel over the circuit-switched network from the first network gateway.
The local facsimile machine 105 transmits fax relay data 107 to a gateway 200A over the packet-switched network 110. In some embodiments, the fax relay data 107 may be converted to packet fax relay data 115 by an intermediate gateway or other networking device (not shown) prior to traversing the packet-switched network 110. The packet fax relay data 115 may correspond to at least a portion of fax pages scanned for real time fax relay protocol transmission, e.g., T.30 protocol, to the remote facsimile machine 135. The local facsimile machine 105 may packetized the fax relay data 107 or the packetization may be performed by another device (not shown) located in the packet switched network 110 or between the packet-switched network 110 and the local facsimile machine 105.
The gateway 200A receives packet fax relay data 115 from the packet-switched network 110 and forwards the data over the circuit-switched network 120 for eventual receipt by the remote facsimile machine 135. The gateway 200A identifies another gateway 200B capable of receiving the packet fax relay data 115 in a tunnel 125 through the circuit-switched network 120. In some embodiments, the gateway 200A identifies that gateway 200B is coupled to another packet-switched network 130 and that the gateway 200B may forward the packet fax relay data 115 towards the remote facsimile machine 135 over the packet-switched network 130. When a suitable gateway endpoint for receiving the packet fax relay data 115 in a tunnel 125 through the circuit-switched network 120 cannot be identified, the gateway 200A may convert the packet fax relay data 115 to analog signals, e.g., TDM bearer signals, for transport over the circuit-switched network 120.
The gateway 200A initiates a tunnel 125 through the circuit-switched network 120 for transporting packet fax relay data 115 to gateway 200B. The gateway 200B may send the packet fax relay data 115 received in tunnel 125 to the remote facsimile machine 135 over the packet-switched network 130 according to the real time fax relay protocol. The packet fax relay data 115 received in tunnel 125 may be provided to the remote facsimile machine 135 over one or more additional networks (not shown) and may require additional data conversion and/or tunneling prior to reception at the remote facsimile endpoint 135. In some embodiments, the packet fax relay data 115 may be converted to fax relay data 107 by an intermediate gateway or other networking device (not shown) located in the packet-switched network 130 prior to being forwarded to the remote facsimile endpoint 135 over at least one additional network (not shown).
By tunneling the packet fax relay data 115 through the circuit-switched network 120, instead of converting them to TDM bearer signals, the gateway 200B does not have to reconvert the TDM bearer signals back to packet fax relay data 115 when received from the circuit-switched network 120. Furthermore, since conversions from packet encoding to analog signal encoding require de-jitter buffering of the packet fax relay data 115 to ensure synchronous analog signals are provided over the circuit-switched network 120, tunneling the packet fax relay data 115 through the circuit-switched network 120 may reduce the overall delay in the transmission of fax relay data 107 between local facsimile machine 105 and remote facsimile machine 135.
The signaling controller 220 may generate tunneling signals 225 responsive to the packet indicator 215. The tunneling signals 225 may be sent to gateway 200B over the circuit-switched network 120 via a circuit-switched network interface 230 or through out-of-band signaling. When the tunneling signals 225 are sent in-band over the circuit-switched network 120, the signaling controller 220 embeds the tunneling signals 225 into, e.g., a TDM data stream, without affecting the voice or fax quality of the TDM connection. In some embodiments, the signaling controller 220 may embed the tunneling signals 225 in every voice or data 8 samples.
The tunneling signals 225 may request identification of a recipient endpoint, i.e., gateway 200B, including whether the recipient endpoint is capable of receiving tunneled packet fax relay data 115. The recipient endpoint may respond to the tunneling signals 225 affirming that it is capable of receiving tunneled packet fax relay data 115 from the gateway 200.
In some embodiments, the signaling controller 220 may generate tunneling signals 225 that broadcast the capabilities of the gateway 200. The broadcasting may be performed periodically, intermittently, sporadically, etc. Thus, all gateways 200 receiving the broadcast will understand the capabilities of the transmitting gateway 200.
In some embodiments, the signaling controller 220 may access a tunnel memory 260 to determine if there is a recipient endpoint that has previously received tunnel data from the gateway 200. The tunnel memory 260 may include one or more identifiers associated with recipient endpoints capable of receiving tunneled data. When there is a recipient endpoint identified in the tunnel memory 260, the signaling controller 220 may generate a tunneling signal 225 that alerts the recipient endpoint of a tunnel and data that the gateway is going to provide. In some embodiments, the signaling controller 220 determines to not generate tunneling signals 225 responsive to identifying the recipient endpoint in the tunnel memory 260. The tunnel memory 260 may also identify recipient endpoints that cannot receive tunnel data. The signaling controller 220 may determine to not send tunneling signals 225 responsive to identifying a recipient endpoint that cannot receive tunnel data.
When receiving tunneling signals 225, the circuit-switched network interface 230 forwards them to a signaling detector 240 for analysis. The signaling detector 240 may determine to send the packet fax relay data 115 to the recipient endpoint responsive the tunneling signals 225 and prompt a tunneling mechanism 250 to initiate a tunnel through the circuit-switched network 120 for the transport of the packet fax relay data 115. In some embodiments, the tunneling mechanism 250 may include a de-jitter buffer (not shown) for storing and organizing packet fax relay data 115 received from the packet-switched network interface 210 when prompted by the signaling detector 240, for example, during non-tunneling events.
The signaling detector 240 may also provide information to the signaling controller 220 for use in updating the tunnel memory 260 or for responding to the received tunneling signals 225. In some embodiments, when there is a broadcast by a gateway 200 received at circuit-switched network interface 230, the receiving gateway 200 may update the tunnel memory 260 according to the contents of the broadcast.
The tunneling mechanism 250 may include some signaling (not shown) within transmissions through the circuit-switched network 120 indicating to the recipient endpoint that the data included is packet encoded. This signaling may be similar to the tunneling signals 225 sent by the signaling controller 220. In some embodiments, the signaling controller 220 provides the signaling (not shown) within transmissions through the circuit-switched network 120 indicating to the recipient endpoint that the data included is packet encoded
In a block 320, the gateway 200A identifies at least one remote gateway 200B to receive the packet fax relay data 115 in a tunnel through a circuit-switched network 120. The gateway 200A may identify that gateway 200B can receive tunnel packet fax relay data 115 by sending tunneling signals 225 to the gateway 200B requesting a response including the capabilities of the gateway 220B, or by accessing a tunnel memory 260 to determine whether the gateway 200B has received tunneled data previously or if the gateway 200B sent a previous broadcast of its capabilities.
The gateway 200A may also determine whether gateway 200B should receive packet fax relay data 115 in tunnel 125 through circuit-switched network 120. For instance, when gateway 200B is not coupled to another packet-switched network 130 in a tandem IP network configuration, the gateway 200A may optionally determine to convert the packet fax relay data 115 instead of tunnel the data 115 through circuit-switched network 120.
In a block 330, the gateway 220A transmits the packet fax relay data 115 to gateway 200B in a tunnel 125 through the circuit-switched network 120. The gateway 220A may initiate the tunnel 125 responsive to identifying that gateway 200B can receive tunneled packet fax relay data 115, as described above referencing block 320.
One of skill in the art will recognize that the concepts taught herein can be tailored to a particular application in many other advantageous ways. In particular, those skilled in the art will recognize that the illustrated embodiments are but one of many alternative implementations that will become apparent upon reading this disclosure. Although
The preceding embodiments are exemplary. Although the specification may refer to “an”, “one”, “another”, or “some” embodiment(s) in several locations, this does not necessarily mean that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment.
