|Publication number||USRE42995 E1|
|Application number||US 11/197,723|
|Publication date||Dec 6, 2011|
|Filing date||Aug 3, 2005|
|Priority date||Jul 26, 1999|
|Also published as||US6801341|
|Publication number||11197723, 197723, US RE42995 E1, US RE42995E1, US-E1-RE42995, USRE42995 E1, USRE42995E1|
|Inventors||Neil Raymond Joffe, Ilya Umansky|
|Original Assignee||Cisco Technology, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (17), Referenced by (4), Classifications (23), Legal Events (1)|
|External Links: USPTO, USPTO Assignment, Espacenet|
1. Field of the Invention
This invention relates generally to communications systems using fax devices for transmission of fax information through packet switching networks and particularly to transmission of fax information wherein modulation/demodulation of fax information occurs independently of and remotely from the protocol implementation used prior to transmission of information.
2. Description of the Prior Art
Facsimile (Fax) machines are commonly employed in modern communications systems. Typically, two fax machines are in communication with each other exchanging messages faxed by users thereof. The messages transmitted by a fax machine are generally in analog format and are often transmitted through a Public Switching Telephone Network (PSTN) as depicted in
Messages are exchanged between fax machines using protocol information either located within the hardware or implemented by execution of the software within the fax machine. One of the protocols is the protocol T.30 which carries information such as that relating to the size of the fax page, the type of compression technique being employed on the fax data and the like.
Other protocols, such as the T.4/T.6, are used for transferring information regarding fax pages and the actual content of the fax message. Information in conformance with the various protocols mentioned hereinabove is modulated prior to transmission thereof. The modulation protocols used to send fax messages are sometimes referred to as V-series modulation protocols such as V.21, V.29, V.17, V.33 and V.27ter. The various V-series modulations differ according to their speed of transmission. For instance, the T.30 protocol is transmitted using the V.21 modulation protocol which causes operation at a relatively slow speed of 300 bits/sec whereas the T.4/T.6 protocols are transmitted using faster modulation protocol, such as the V.17, V.29, V.33 and V.27ter. In
In addition to the protocol subsystem 22 and the data pump 24, the fax machine 12 generally includes the scanner 26 and the memory 28. Scanner 26 scans pages of information that are to be faxed as the pages are passed through the fax machine and transforms them into black and white pixels. The pixel information is then encoded and stored in the memory 28 of the fax machine.
Alternatively, a fax machine could be incorporated in a personal computer (PC). In such a case the data pump component of the fax machine is placed on a modem card and the component of the fax machine which executes the T.30 and T.4/T.6 protocols is a software program on the PC. The modem card is physically connected to the PC through a cable and for this reason cannot be placed in a location too remote from the PC such as in a network.
Yet another mode of communication between the fax machines 12 and 14, not shown in
Sending fax messages via fax relay can be considerably less expensive than the method of communication shown in
Access servers are located at the edges of the network. In fax relay, when a fax message is received by an access server, such as the AS5300 having fax relay capability, the message is demodulated and sent across the network to a receiving access server which is physically closest to the receiving fax machine. Messages transferred between access servers through the network are in packet form. Packets are unbundled by the receiving access server and subsequently remodulated into the original fax message and sent to a local PSTN using T.30 and T.4/T.6 protocols. The PSTN then sends the fax message to the receiving fax machine. Messages are sent from one point in the network to another point in the network using a propriety proprietary fax relay protocol or a standardized protocol such as the T.38 protocol.
An access server, such as the AS5300, does not decode the fax messages in the T.30 and T.4/T.6 protocols and the original fax information that is encoded in these protocols passes from one access server to another transparently. Consequently, no change in the contents of the fax messages takes place as the messages are transmitted through the network via the access servers. It is the fax machine which can implement the T.30 and T.4/T.6 protocols, using the protocol subsystem 22 of
Fax relay is a one-to-one method of transmitting fax messages between two fax machines. Accordingly, there is an originating fax machine which dials the number of a receiving fax machine and sends the message through an intermediate network. However, it is desirable to send fax messages from the originating fax machine to an access server which may be located at any point in the network. Once received by the access server, the message could either be sent to a receiving fax machine or to an email recipient in the from of an email message. Alternatively, the message could simply be stored somewhere in the network for later delivery. The latter option is particularly useful when the receiving fax machine is busy in which case the fax message is still received by the network and stored somewhere therein. The fax message can then be transmitted to the receiving fax machine at a later time when the latter is no longer busy. Such a mode of transmitting fax messages has the effect of distributing the functionality of the fax machine throughout the network.
Therefore, the need arises to distribute the functionality of a fax device through a packet switching network thereby increasing system capacity and allowing for readily altering features of a fax device without the need for additional hardware.
Briefly, an embodiment of the present invention includes a fax communication system for communicating fax information transmitted from a sending fax device to a fax recipient through a packet switching network. The sending fax device includes a data pump for modulating and demodulating fax information and a protocol subsystem for encoding and decoding the modulated fax information. The fax sending fax device modulates the fax information prior to transmission thereof. At least one access server is coupled between the sending fax device and the fax recipient and within the packet switching network network. At least one of the access servers receives modulated fax information from the sending fax device and demodulates the received fax information. The fax relay server is responsive to the demodulated fax information and operative to decode the received demodulated fax information for transmission thereof to the fax recipient, wherein the at least one access server and fax relay server function as a network distributed fax device allowing for expansion of fax functionality throughout the network while preserving the reliability and robustness of the network.
The foregoing and other objects, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments which make reference to several figures of the drawing.
Referring now to
The IP network 46 is shown to include a network 44. In one embodiment of the present invention, the IP network 46 network 44 is the Internet and in another embodiment, it is a WAN (such as Cisco WAN). Alternatively, other types of network may be employed without departing from the scope and spirit of the present invention. The IP network 46 is further shown to include a fax relay server 50 and a plurality of access servers (or access routers), three of which are shown in
Inside the IP network 46, information is sent from one point to another using any fax relay protocol which is the international standard for fax relay protocol. Accordingly, fax relay protocol is sent from the access server 40 to the network 44 through transmission line 42 and from the network 44 to the access server 62 through transmission line 60. Access servers 62 and 56 are coupled to each other via the communication line 58 and access servers 40, 56 and 62 are linked to the fax relay server 50 through the transmission lines 48, 54 and 52, respectively. Transmission line 72 couples the fax relay server 50 to a mail server 74, which is in communication with the email recipient 78 through a communication line 76.
Fax machines 32 and 70, shown in
The V-series modulations are modulation protocols of varying speeds which are used in sending fax information pursuant to the T.30 and T.4/T.6 protocols. For example, the V.21 protocol, which causes a relatively slower speed of transmission, i.e. 300 bits/sec, is used to send the T.30 protocol. The other modulation protocols such as V.29, V.17 and V.33 operate to cause faster speeds of transmission and are used to send the actual content of the fax massage as encoded in the T.4/T.6 protocols.
In the communication network 30 of
In traditional fax relay, fax messages in the form of T.30 and T.4/T.6 protocols, originating from the fax machine 32, pass through the PSTN 36 and reach the access server 40. The access server 40 demodulates fax messages and transmits the same across the network 44 in the form of packets. Inside of the access server 62, the packets are unbundled and re-modulated and then re-transmitted through the PSTN 66 to the receiving fax machine 70.
The access servers in the IP network have the capability of modulating and demodulating fax messages in the same way as that performed by the data pump of a typical fax machine performing modulation and demodulation functions. For this reason, access servers in the IP network 46 are sometimes referred to as data pumps. However, an access server cannot decode the messages in the T.30 and T.4/T.6 protocols and the information in such protocols passes through an access server transparently. It is in a component of a fax machine, such as the protocol subsystem 22 in
Information in the form of packets is transmitted from one point of the IP network 46 to another point using any proprietary fax relay protocol such as the T.38 protocol. For instance, the access server 62 communicates with the access server 56, the fax relay server 50 and the network 44 by sending and receiving fax relay protocols through the transmission lines 58, 52 and 60, respectively. The access servers are generally located at the edges of the IP network 46 and are alternatively referred to either as fax relay end points or data pumps. It is recalled that the reason for calling an access server a data pump is due to the access server's ability to modulate and demodulate the T.30 and T.4/T.6 protocols in the same manner that a data pump in a fax machine performs modulation/demodulation.
In one embodiment of the present invention, as shown in
In light of the above, each of the access servers in the IP network 46 has a dual purpose. Each access server can act as a fax relay point so that it can receive and transmit fax messages in the form of packets. Alternatively, the access server along with the fax relay server 50 can act as a fax machine.
The fax message, when located within the fax relay server 50, is stored on a disk and from there can be transmitted to a number of destinations. For instance, the fax message can either remain in storage for later delivery, transmitted to a printer (not shown in
The actual reception and transmission or routing of the packets is performed by the IOS 82 in
The part of the fax relay server 50 which implements the T.30 and T.4/T.6 protocols can be placed anywhere in the IP network 46. For instance, it can be placed inside any network device such as the AS5300, an example of which is the access server 40 in
There are two main disadvantages in placing the protocol subsystem 86 which implements the T.30 and T.4/T.6 protocols within the access server 40. The first disadvantage arises from the subsystem 84 acting as a data pump, i.e. performing modulation/demodulation functions as explained in the previous paragraph. The modulation/demodulation subsystem 84 and the protocol subsystem 86 together constitute a fax machine, i.e., the access server 40 operates as a fax machine having modulation/demodulation and encoding/decoding capabilities of a fax machine. However, rather than using an access server in place of a fax machine, an actual fax machine could have been introduced into the IP network 46.
The second disadvantage associated with placing the protocol subsystem 86, which implements the T.30 and T.4/T.6 protocols within the access server 40 is due to the lack of secondary storage capability within the access server 40. An example of a secondary storage facility is a hard disk. As the number of arriving packets which carry fax messages increases, storage capacity in the temporary storage 92 becomes more limited until the storage facility has exceeded its capacity. As a result, lack of storage capacity presents a major hindrance to the growth of fax communication within an IP network when the protocol subsystem 86 is placed inside of the access server.
It is therefore preferable to maintain the software which implements the T.30 and T.4/T.6 protocols independent of any access servers by placing the software in a server such as the fax relay server 50 shown in
Fax machines 102–112 are coupled to the access servers 114, 116 and 118 through the communication lines 120–130. Fax messages transmitted through the communication lines 120–130 are in the form of T.30 and T.4/T.6 protocols. Access servers 114, 116 and 118 are coupled to the network 44 through the transmission lines 134, 136 and 138, respectively while the fax relay server 50 is coupled to the network 44 through the transmission line 132. The access server 114 is coupled to the access server 116 and the latter is coupled to the access server 118 through the transmission lines 140 and 142, respectively.
Fax messages in the form of packets are transmitted inside the IP network 146 using any fax relay protocol such as the T.38 protocol. The latter, being the international standard for fax relay protocol, allows the fax relay server 50 to communicate with any other type of access server in the IP network 146. The network 146 could be any one of the variety of IP networks, such as IP over Asynchronous Transfer Mode (ATM) network or IP over frame relay network. The IP network, for the implementation of the present invention need be fast enough to support fax relay. The minimum speed required for fax relay is about 19.2 kbits/sec, however, large distributed networks typically operate at much higher speeds such as 100 Mbits/sec.
In one embodiment of the present invention, as shown in
The fax messages stored on disks inside the fax relay server 50 can either be routed to any point in the IP network 146 or can be sent directly to a printer for printing. Alternatively, the fax relay server can transform the fax messages into TIFF files and send the latter as email messages to another mail server which can in turn distribute them to any email recipient connected to the IP network 146. Furthermore, the network distributed fax device 100 shown in
Next, at step 202, a determination is made as to whether or not the receiving fax machine is busy with other tasks or free to receive the fax message or whether or not the destination of the fax message is the network. If the destination of the fax message is the network, the fax transmission will end when the fax relay server receives the fax message. If the receiving fax machine is busy (when the access server tries to establish communications with the receiving fax machine, it receives a busy tone if the receiving fax machine is busy) or if the destination of the fax message is the network, the process proceeds to step 208.
If, however, at step 202, it is determined that the receiving fax machine is free, the fax message is transmitted by the access server to the receiving fax machine as indicated at step 206. The fax message, on its way to the receiving fax machine, may conceivably pass through another access server before arriving at the receiving fax machine's location.
At step 208, if the message is stored for the purposes of waiting for the availability of the receiving fax device, the fax message is stored within the fax relay server for subsequent transmission thereof to the receiving fax machine. At step 208, if the message's destination is the network, the fax transmission ends at step 208 with the fax message reaching the fax relay server.
It is also possible that the fax message is intended either to be received by an email recipient connected to the IP network 146 or simply by a printer connected to the same network or perhaps by another type of fax receiving device. In either of these cases, following step 202, the fax message is forwarded to the fax relay server 50 for storage therein as indicated in step 208. The fax relay server 50 can either send the fax message to a printer device, which is indicated by the determination at 210 where the fax relay server decides if the fax message is intended to be sent to a printer and then transmits the message at step 212 to the destination printer. Alternatively, the fax relay server determines if the fax message is to be sent to an email recipient, as indicated at 214 and then, at step 216, transforms the same into a TIFF file(s) for transmission to an email recipient depending upon the destination of the fax message as specified by the T.30 protocol. If the destination of the fax message is other than an email recipient, printer or a fax machine, the fax message is sent to the specified destination at step 218.
The network distributed fax device 100 is capable of scaling to a very large size. That is, the latter can grow in size without requiring a substantial investment as more access servers, which act as data pumps, are distributed in the IP network 146. This advantage is made possible by the presence of a centralized fax relay server 50 which implements the T.30 and T.4/T.6 protocols in one embodiment of the present invention as shown in
Moreover, the fax relay server 50 of the network distributed fax device 100 makes the IP network more robust. That is, by keeping the implementation of the T.30 and T.4/T.6 protocols inside of the fax relay server 50 and out of the access servers 114–118, the latter access servers are allowed to efficiently perform their main function which is routing of the packets at a very fast rate thereby preserving the reliability of the IP network 146. Otherwise, each access server would be required to participate in implementation of the T.30 and T.4/T.6 protocols which could consume some of the time of the CPU within the access server thereby resulting in the latter being less reliable. The access server comprises the core of the IP network and as such has to be highly reliable in order to operate at very fast speeds. For example, a typical rate of switching packets for the AS5300 access server is 125,000 packets/sec. The present invention preserves the reliability of the access server by dedicating the implementation of the T.30 and T.4/T.6 protocols to the fax relay server 50.
Yet another advantage of using the network distributed fax device 100 lies in its capability to store fax messages and to deliver them at a later time. More specifically, consider the case where the fax machine 102 is sending a fax message to the fax machine 104. If the latter fax machine is busy with other tasks, the fax message is still sent through the access server 114 and the network 44 to the fax relay server 50 where it is stored on a disk. The fax message is then sent to its destination, i.e. fax machine 104, at a later time when the latter is no longer busy. Consequently, the originating fax machine 102 would no longer be occupied with trying to transmit the original fax message and can attend to other tasks.
It should be mentioned that there are currently fax products available in the market with modems being on the network. However, the protocol used for communication in such products is not the fax relay protocol and consequently these prior art fax products are not able to achieve the level of scaling, reliability and interoperability that is enjoyed when using the fax relay protocol as is the case in the present invention. Limitations in scaling in the aforementioned products is mainly due to the fact that more hardware, such as modems, is required in order to reach more destination points in the network. Placing more hardware on the network, however, increases the cost of sending fax transmissions thereby increasing costs associated with the expansion of such network-based fax products. Further problems with such prior art systems include having to place a PC (or processor) fairly close to the modem within the network because the protocol used to communicate information between the two is not well-suited for applications where these two devices are placed far away from one another.
The fax relay server extracts T.30/T.4/T.6 data from the IP packets in which they are transported in the IP network. These IP packets and protocol associated therewith are called fax relay. One standardized implementation of a fax relay protocol is called T.38. Once T.30/T.4/T.6 information is extracted from fax relay packets, the fax server runs T.30/T.4/T.6 protocols to communicate to the fax message recipient, which may be another fax server of IP distributed fax device or traditional fax machine in PSTN or a printer or an email recipient.
In the transmitting session, the steps mentioned above follow one another in exactly the reverse sequence. Namely, fax data 160 arrives at the fax relay server 50 where it is encoded in the form of T.4/T.6 protocols at step 156. At step 154 the T.4/T.6 protocols are complemented with the T.30 protocol which carries additional information such as the type of compression used on the fax data. Finally, the T.30 and T.4/T.6 protocols are converted to either T.38 protocol or any other fax relay protocol and sent out as packets 162 to other parts of the IP network 146.
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|U.S. Classification||358/407, 358/404, 358/405, 358/1.15, 358/402, 358/403, 358/406|
|International Classification||H04L12/58, G06F3/12, H04N1/00|
|Cooperative Classification||H04N1/00209, H04L12/5835, H04N1/33338, H04L51/066, H04N1/33346, H04N1/00244, H04N2201/0093|
|European Classification||H04L12/58C2, H04N1/00C3G, H04N1/00C3K, H04N1/333G, H04N1/333P, H04L51/06B|