Fax over IP FAQ
- What is the difference between real-time FoIP and store and forward faxing?
- If a fax is sent by a fax machine to a DM Fax Server that’s T.38 enabled, is it sent as T.30 end to end?
- Is it possible to save on long distance charges with DM Fax Server and FoIP?
- Can DM Fax Server be connected directly to a Cisco Call Manager?
- Can DM Fax Server, with the Brooktrout TR1034 fax board, ever be used for faxing over IP and PSTN at the same time, or from the same server?
- How many IP fax machines are out in the market?
- How are legacy fax machines affected? Do they know they are communicating with a FoIP DM Fax Server?
- How secure is DM Fax Server and FoIP?
- Does DM Fax Server for FoIP use fewer ports/channels than DM Fax Server for PSTN-based faxing?
- Does a FoIP-enabled DM Fax Server send and receive faxes at v.17 (14.4 KB/sec) or v.34 (33.6 KB/sec)?
- Will the faxes that I receiveover an IP network using DM Fax Server contain an IP address or the sending fax number?
What is the difference between real-time FoIP and store and forward faxing?
There are currently two ways to implement FoIP. The first standard, T.37, is used mainly for store-and-forward faxing. It defines elements of how Internet email can be adapted to support a facsimile service and specifies the format in which fax is to be delivered as an e-mail attachment. The second standard, T.38, defines the protocol for real-time delivery of FoIP. With T.37 FoIP, the fax is sent over IP as e-mail attachment and delivered directly to an email address or via a gateway to a Group 3 fax device over the public switched telephony network (PSTN). While T.37 allows for cost savings through toll arbitrage, from a user’s perspective it is a store and forward model and is not real time. Given the current state of the Internet email infrastructure, there are limitations on the ability to receive confirmation that a fax was successfully delivered to its destination. T.37 confirmations rely on the store and forward mechanism known as Delivery Service Notification (DSN). Unless all email relay servers along the IP delivery path support DSN, a request for confirmation will not be satisfied. Even if DSN is supported on the entire IP route, there may be delays in relaying the confirmation back to originating T.37 device due to network congestion, since the DSN is generated asynchronously and is not part of the original T.37 communication.
With T.38 real-time FoIP, faxes are delivered in real-time exactly like a regular fax call. The two fax devices synch up and send data over a local telephone connection, with an IP leg between the two local connections. If the fax is busy, the caller gets a busy signal and the user has the option to retry sending later or to revert to store-and-forward mode as a transportation mechanism. A key point is that the confirmation takes place during the T.38 fax session, not at a later point. Store-and-forward-mode FoIP works like email. The caller sends the fax message to a server, which sends it to another server, which sends the fax to the recipient. Eventually, the caller is notified whether the fax made it to the destination.
If a fax is sent by a fax machine to a DM Fax Server that’s T.38 enabled, is it sent as T.30 end to end?
The fax sent by a fax machine will be T.30 end to end. When that fax hits the IP gateway, the gateway will encapsulate the T.30 protocol data in the T.38 packets, which are then sent to the DM Fax Server containing the Brooktrout TR1034 or SR140 fax board. The fax call is T.30 end-to-end, it’s just that part of the call is over a traditional phone network, and part of the call is over a packet-switched network. This is different from G.711 pass-through, which is an option on many IP gateways.
Is it possible to save on long distance charges with DM Fax Server and FoIP?
Absolutely. If a fax goes from one gateway/router to another, such as with intra-company faxing over a company’s WAN, then the fax transmission would not leave the IP network and long-distance charges would be reduced. This is one of the main benefits of implementing Imecom’s DM Fax Server for FoIP in an enterprise environment.
Can DM Fax Server be connected directly to a Cisco Call Manager?
Yes. In this case the Cisco Call Manager would act as a PBX/gateway, in which the Call Manager would either pass on the T.38 packets or re-package them into T.30 packets.
Can DM Fax Server, with the Brooktrout TR1034 fax board, ever be used for faxing over IP and PSTN at the same time, or from the same server?
No. The TR1034 fax board needs to be set for either IP or PSTN fax transmission, but not both at the same time. In addition, you cannot set up a single DM Fax Server with two TR1034 boards where one is sending faxes over IP and the other over PSTN – this will not work.
How many IP fax machines are out in the market?
According to Peter Davidson Consulting estimates, there is an install base of approximately 100 million T.30 PSTN based fax machines installed today. There are currently no estimates on the installed base or growth of IP-based fax machines, although IP faxing has been available as an optional feature on some fax machines since 1999.
How are legacy fax machines affected? Do they know they are communicating with a FoIP DM Fax Server?
Fax machines still communicate using the T.30 protocol, and will have no idea that the DM Fax Server on the other end is an IP-enabled fax server connected to an IP network. This is because DM Fax Server is still communicating using T.30 protocol. On the packet network, the T.30 protocol has to be encapsulated as packets by the T.38 protocol. But it’s still the same T.30 protocol being spoken end-to-end.
How secure is DM Fax Server and FoIP?
With any IP network, you should always take the appropriate measures to ensure their network is secure physically and logically from external attacks by viruses, malicious users or other intrusions. If security from internal attacks is a concern, the IP network may be configured to use VPNs between the T.38 endpoint and a gateway. With a properly configured IP network in place, you will not be presented with additional security concerns when implementing real-time FoIP into the company network. Even if a malicious packet was to penetrate the firewall, the Imecom DM Fax Server only allow only for the transfer of T.4 and T.6 fax images, and not data. A non-standard fax or non-fax packet will be ignored by DM Fax Server. A good summary of potential threats and security responses for FoIP in general can be found in RFC 2305.
Does DM Fax Server for FoIP use fewer ports/channels than DM Fax Server for PSTN-based faxing?
No. Because DM Fax Server in a FoIP configuration sends and receives faxes is in real-time, the same number of channels is still needed. A fax session will remain open until the transmission is completed. Furthermore, because the faxing is in real-time, the gateways/routers don’t cache any of the data, so again the same number of ports/channels is required.
Does a FoIP-enabled DM Fax Server send and receive faxes at v.17 (14.4 KB/sec) or v.34 (33.6 KB/sec)?
This is entirely dependent on the IP-PBX and/or VoIP Gateway being used. The current implementations for real-time FoIP using Dialogic Brooktrout TR1034 and SR140 series fax board products supports v.34 (33.6 KB/sec) fax. This only applies when the SR140 or TR1034 connects to a Dialogic Media Gateway (3000 or 4000 series). If the SR140 or TR1034 connects to a non-Dialogic IP-PBX or VoIP Gateway, e.g. Cisco or Avaya, then the maximum standard used will be v.17 (14.4 KB/sec). Some VoIP gateways may support less than v.17. Imecom recommends checking with the IP-PBX and/or VoIP Gateway vendor for fax standard specifications.
Will the faxes that I receive over an IP network using DM Fax Server contain an IP address or the sending fax number?
The faxes will still contain the sending machine phone number. This information is exchanged as part of the T.30 protocol, and will still be available when faxes are sent/received over an IP network. For example, if the sending fax machine has phone number 603.569.0609, and it sends a fax to a TR1034 board that is in IP mode, the received fax will show that it came from 603.569.0609.
