Abstract:
Computer communications that are to be recorded are visible to a network interface on a recording computer. The network interface receives the packets to be recorded. The network layer of the recording computer implements a subset of the normal IP module in the network layer. Instead of checking every IP packet, the IP module in the network layer assumes that most IP packets are correctly addressed, internally consistent and of the expected protocol type. The recording computer allocates the received packets to a recording session based upon the value of a field that is at a fixed position within the packet. Packets that are allocated to a session are recorded or associated with other packets that have been allocated to the same session.

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/015,621, filed Jan. 17, 2008, entitled “DEDICATED NETWORK INTERFACE,” which claims the benefit of priority to U.S. Provisional Patent Application No. 60/951,404, entitled “COMMUNICATIONS RECORDING”, filed on Jul. 23, 2007, all of which are herein incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The invention is related to the field of recording communications. 
     TECHNICAL BACKGROUND 
     Computer communications carried over computer networks may be recorded. Typically, a computer is used to collect and record the communications. The collection of computer communications is done in three main ways. “Promiscuous mode tapping” collects all packets on the network and then the recording computer filters these to determine which to keep. In a “conference bridge approach,” the recording computer becomes a participant in the call and receives packets from the other participants and/or from a conference bridge. Lastly, a party (e.g. computer) in the communication may forward packets or derivatives of packets that form the communication session to the recording computer. 
     The recording computer typically taps the network or receives the communication to be recorded over an industry standard Network Interface Card (NIC) which supports a protocol stack. This would typically include the TCP/IP stack. 
     However, the recording application can be very demanding of the performance capabilities of the recording computer. For example, when recording communications using promiscuous mode tapping on some of the most advanced networks, the recording computer may receive data at a rate of 10 gigabits per second. That may translate to as many as 1.25 gigabytes per second that need to be processed, filtered, and ultimately recorded by the recording computer. This amount of processing may overload some recording computers, thereby resulting in the loss of some of the communications that should have been recorded. Accordingly, to prevent data loss and allow the use of less expensive computers as recording computers, there is a need in the art for more efficient recording systems. 
     SUMMARY 
     Computer communications that are to be recorded are visible to a network interface on a recording computer. The network interface receives the packets to be recorded. The network layer of the recording computer implements a subset of the normal IP module in the network layer. Instead of checking every IP packet, the IP module in the network layer assumes that most IP packets are correctly addressed, internally consistent and of the expected protocol type. The recording computer allocates the received packets to a recording session based upon the value of a field that is at a fixed position within the packet. Packets that are allocated to a session are recorded or associated with other packets that have been allocated to the same session. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. While several embodiments are described in connection with these drawings, there is no intent to limit the disclosure to the embodiment or embodiments disclosed herein. On the contrary, the intent is to cover all alternatives, modifications, and equivalents. 
         FIG. 1  is a block diagram illustrating a system for recording computer communication sessions. 
         FIG. 2  is a flow diagram illustrating a method for recording computer communication sessions. 
         FIG. 3  is a block diagram illustrating a system for recording computer communications. 
         FIG. 4  is an illustration of a value at a fixed position within a packet that may be used to allocate packets. 
         FIG. 5  is a flow diagram illustrating a method of resisting packet errors or service disruption attacks. 
         FIG. 6  is a flow diagram illustrating a method of providing packets suitable for transmission by a recording computer. 
         FIG. 7  is a block diagram illustrating a computer system. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1-7  and the following description depict specific embodiments of the invention to teach those skilled in the art how to make and use the best mode of the invention. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these embodiments that fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple embodiments of the invention. As a result, the invention is not limited to the specific embodiments described below, but only by the claims and their equivalents. 
       FIG. 1  is a block diagram illustrating a system for recording computer communication sessions. Communication recording system  100  includes computers  130  and  131  operatively coupled to network  120 . Recording computer  140  is also operatively coupled to network  120 . Network  120  may be a Local Area Network (LAN) or a Wide Area Network (WAN) or some other form of computer communications network. Recording computer  140  includes network interface  102 . Network interface  102  is operatively coupled to network  120 . Network interface  102  is also operatively coupled to network subset layer  104 . Network subset layer  104  is operatively coupled to packet allocation  106 . Packet allocation  106  is operatively coupled to packet storage  110 . Packet storage includes session # 1   111 , session # 2   112  and session #N  113 . Packet allocation  106  is operatively coupled to each of sessions  111 - 113 . Sessions  111 - 113  may correspond to a group of packets that a recording application desires to group together or otherwise associate, such as a voice over Internet Protocol call (VoIP), or all the packets to or from a particular internet phone. 
     Computers  130  and  131  may direct communications to be recorded to recording computer  140  via network  120 . An example of communications that can be directed to recording computer  140  are VoIP telephone calls. For example, to record the contents of a VoIP call between computers  130  and  131 , a VoIP application running on computer  131  may send packets to recording computer  140  as if it were also a participant in a conference call. Recording computer  140  could then record the VoIP packets (grouped, for example, as a session # 1   111 ) so that the audio contents of the call may be reconstructed and replayed. In another example, computer  131  may store a local copy of the VoIP or digitized version of a Plain Old Telephone System (POTS) call. At a certain time, perhaps when network  120  and/or computer  131  is not busy, this local copy is then sent to recording computer  140  via network  120 . 
     Other forms of directing communications to recording computer  140  are also possible. For example, using port mirroring, all of the packets that come from, go to, or pass through, a given network router, switch, or other device may be directed to recording computer  140  by that device. In an example, these mirrored packets may be encapsulated in order to specify the IP address of NIC  102  thus ensuring proper routing of the packet on its way to NIC  102 . In another example, the mirrored packets may be encapsulated and sent as the payload of an RTP packet stream. The destination IP address of these RTP packets may be set to that of the recorder&#39;s dedicated NIC  102 , and the UDP port number field is set to a value representing a specific recorded session. Details of which UDP port number relates to which recording session, such as source and destination IP addresses and ports, may be exchanged separately between recording computer  140  and the device that encapsulates the packets. In this case, depending upon the method chosen, recording computer  140  may or may not need to un-encapsulate and/or forward those packets back to network  120  (or another network, not shown) so they may ultimately be routed to the appropriate destination. In another example, a similar approach may be used with a TCP socket in place of an RTP packet stream. This would allow more reliable transmission of the stream. This increased reliability is particularly important in cases where the occasional loss of a packet is unacceptable. For example, when email is being recorded by recording computer  140 , the occasional loss of a packet as may occur when using RTP is unacceptable. 
     The operative coupling of recording computer  140  and network  120  may be described by a reference model for communications and network protocol design. This description may be referred to as the TCP/IP or Internet reference model and includes five layers. These layers, which are all operatively coupled, may be referred to as the physical layer, the data link layer, the network/internet layer, the transport layer, and the application layer. The physical layer may be implemented by an Application Specific Integrated Circuit (ASIC) or other analog and digital electronics. The elements of the physical layer may reside in network interface  102 . The data link layer may also be implemented on network interface  102  by firmware cooperating with hardware driver software in the operating system of recording computer  140 . The network layer and transport layer may be implemented in the operating system software running on recording computer  140 . 
     After network interface  102  receives a packet and processes the packet through the physical and data link layers into a form suitable for the network layer, it passes the packet to the network subset layer  104 . Network subset layer  104  processes and responds to the packets received from the data link layer to implement at least one of the network layer functions. For example, network subset layer  104  may check the destination address field of the header of a packet in Internet Protocol (IP) form. Examples of IP packet formats are given by IPv4 and IPv6. 
     In another example, the data link layer may determine that the packet is an Address Resolution Protocol (ARP) request. The network subset layer  104  may then respond appropriately. In another example, the data link layer may determine that the packet is an IP packet. In this case, the network subset layer  104  may pass the packet to the transport layer (e.g. packet allocation  106 ) without further checks or processing. In addition, network subset layer  104  may also implement other functions or protocols necessary for recording computer  140  to perform the function of recording packets directed to it via network  120 . 
     Packet allocation  106  receives packets from network subset layer  104 . Packet allocation  106  may be part of a transport layer or may be implemented separately. In an embodiment, packet allocation  106  may accomplish the function of allocating packets passed to it by the network layer by examining a value at a fixed location, or offset, in each packet and using this value as a basis to identify a session. 
     In an embodiment, if the packet is formatted as a User Datagram Packet (UDP), then the value at the fixed location may be, for example, the destination port number of the packet. In an embodiment, packet allocation  106  may allocate packets based upon the destination port number of the packet. For example, packet allocation  106  may allocate a packet to session # 1   111  when the destination port number of the packet is 1. Packet allocation  106  may also allocate a packet to session # 2   112  when the destination port number of the packet is 2. This function may also be used with arbitrary port number-session number pairings such as allocating packets with a destination port number of 73 to session #N  113  where “#N” is an arbitrary identifier of the session these packets are to be associated with such as 99, or “VoIP call between 970-555-1234 and 408-555-9876 from 11:05 to 13:07 on Oct. 9, 2007”, or email “message-ID=14432593.1191958317010.” Once packets are allocated to a session, they are stored in packet storage  110  and associated with the one of sessions  111 - 113  to which they were allocated. 
     Packets may be allocated to a particular recording stream and sent to packet storage  110  without further processing by the transport or application layers, thus saving machine cycles or other resources on recording computer  140 . These machine cycles and resources are saved by not subjecting the packets sent to packet allocation  106  to all of the examination normally undertaken by a full network layer. Specifically, the assumption that all IP packets received will be for a single IP address and/or that only UDP packets will be received allow the elimination of at least tests on the IP address and IP protocol type fields respectively. Similarly, recording computer  140  may be configured to rely upon the checksum of the data link layer to ensure the integrity of a transmission. This avoids testing the various checksums within the IP elements of the message. Testing for a valid RTP header may also be skipped as well as confirming that the packet length is consistent with the IP length indication. 
     Packet storage  110  is a storage medium such as a high capacity digital data storage device such as a CD-ROM, magnetic hard drive, DVD drive, DAT cassette, flash memory, or some combination of similar devices. Packet storage  110  may also store other information associated with the stored packets, or sessions  111 - 113 , such as the association between stored packets and sessions  111 - 113  so that the computer communications recorded by recording computer  140  may be reconstructed, replayed, displayed, etc. 
       FIG. 2  is a flow diagram illustrating a method for recording computer communication sessions. In step  202 , an IP packet is received. In step  204 , the received packet is allocated. In an embodiment, a received packet may be allocated by examining the value at a fixed location, or offset, in the packet. 
     In an embodiment, if the packet is formatted as a UDP packet, then the value at the fixed location may be, for example, the destination port number of the packet. In an embodiment, the packet may be allocated based upon the destination port number of the packet. In step  206 , the packet is stored. Accordingly, packets may be allocated by using a very simple method (e.g. based upon a value at a fixed location in the packet) and may then be stored without further processing by the transport or application layers thus saving machine cycles or other resources on the recording computer implementing the method. 
     In an embodiment, the stored packet is associated with other packets that were allocated in the same or similar manner. For example, all packets that were allocated based upon a certain destination port number may be associated with each other. For example, all packets with a destination port number of 2100 would be associated with each other. In an example, if the packets associated with each other were RTP packets, the fields within the stored packet comprising an RTP header allow restoration of the original sequence, detection of missed packets, and removal of duplicate packets as would be done with a standard packet stream such as a VoIP stream. 
     In another example, all packets that arrived between specific events and were allocated based upon a certain destination port number may be associated. For example, all packets received between the “off hook” and “on hook” signals of VoIP calls from 210-555-3210 and with a destination port number of 2300 would be associated with each other. Other examples and associations are possible for reconstructing, replaying, displaying, etc. the packets stored in step  206 . 
       FIG. 3  is a block diagram illustrating a system for recording computer communication sessions. Communication recording system  300  includes computers  330  and  331  operatively coupled to network  320 . Recording computer  340  is also operatively coupled to network  320 . Network  320  may be a LAN or a WAN or some other form of computer communications network. Recording computer  340  includes network interface  302 . Network interface  302  is operatively coupled to network  320 . Network interface  302  is also operatively coupled to network subset layer  304 . Network subset layer  304  is operatively coupled to packet allocation  306 . Network subset layer  304  is also operatively coupled to packet checks  350 . Packet checks  350  is operatively coupled to packet allocation  306  and packet storage  310 . Packet pool  352  is operatively coupled to network subset layer  304 . Packet allocation  306  is operatively coupled to packet storage  310 . 
     Packet storage includes session # 1   311 , session # 2   312 , and session #N  313 . Packet allocation  306  is operatively coupled to each of sessions  311 - 313 . Sessions  311 - 313  may correspond to a group of packets that a recording application desires to group together, such as a voice over IP call (VoIP), or all the packets sent to and from a particular internet phone. 
     Computers  330  and  331  may direct communications to be recorded to recording computer  340  via network  320 . An example of communications that can be directed to recording computer  340  are VoIP telephone calls. For example, to record the contents of a VoIP call between computers  330  and  331 , a VoIP application running on computer  331  may send packets to recording computer  340  as if it were also a participant in a conference call. Recording computer  340  could then record the VoIP packets (grouped, for example, as a session # 1   311 ) so that the audio contents of the call may be reconstructed and replayed. In another example, computer  331  may store a local copy of the VoIP or digitized version of a POTS call. At a certain time, perhaps when network  320  and/or computer  331  is not busy, this local copy is then sent to recording computer  340  via network  320 . 
     Other forms of directing communications to recording computer  340  are also possible. For example, using port mirroring, all of the packets that come from, go to, or pass through a given network router, switch, or other device may be directed to recording computer  340  by that device. In an example, these mirrored packets may be encapsulated in order to specify the IP address of NIC  102  thus ensuring proper routing of the packet on its way to NIC  102 . 
     In another example, the mirrored packets may be encapsulated and sent as the payload of an RTP packet stream. The destination IP address of these RTP packets may be set to that of the recorder&#39;s dedicated NIC  102 , and the UDP port number field is set to a value representing a specific recorded session. Details of which UDP port number relates to which recording session, such as source and destination IP addresses and ports, may be exchanged separately between recording computer  140  and the device that encapsulates the packets. In this case, depending upon the method chosen, recording computer  340  may or may not need to un-encapsulate and/or forward those packets back to network  320  (or another network, not shown) so they may ultimately be routed to the appropriate destination. 
     In another example, a similar approach may be used with a TCP socket in place of an RTP packet stream. This would allow more reliable transmission of the stream. This increased reliability is particularly important in cases where the occasional loss of a packet is unacceptable. For example, when email is being recorded by recording computer  140 , the occasional loss of a packet as may occur when using RTP is unacceptable. 
     The operative coupling of recording computer  340  and network  320  may be described by a reference model for communications and network protocol design. This description may be referred to as the TCP/IP or Internet reference model and includes five layers. These layers, which are all operatively coupled, may be referred to as the physical layer, the data link layer, the network/internet layer, the transport layer, and the application layer. The physical layer may be implemented by an ASIC or other analog and digital electronics. The elements of the physical layer may reside in network interface  302 . The data link layer may also be implemented on network interface  302  by firmware cooperating with hardware driver software in the operating system of recording computer  340 . The network layer and transport layer may be implemented in the operating system software running on recording computer  340 . 
     After network interface  302  receives a packet and processes the packet through the physical and data link layers into a form suitable for the network layer, it passes the packet to the network subset layer  304 . Network subset layer  304  processes and responds to the packets received from the data link layer to implement at least one of the network layer functions. For example, network subset layer  304  may check the destination address field of the header of a packet in IP form. Examples of IP packet formats are given by IPv4 and IPv6. 
     In another example, the data link layer may determine that the packet is an Address Resolution Protocol (ARP) request. The network subset layer  104  may then respond appropriately. In another example, the data link layer may determine that the packet is an IP packet. In this case, the network subset layer  104  may pass the packet to the transport layer (e.g. packet allocation  106 ) without further checks or processing. In addition, network subset layer  304  may also implement other functions or protocols necessary for recording computer  340  to perform the function of recording packets directed to it via network  320 . 
     Packet checks  350  receives packets from network subset layer  304 . In an embodiment, packet checks  350  receives a copy of a subset of the packets that network subset layer  304  sends to packet allocation  306 . For example, packet checks  350  may only receive a copy of one arbitrarily chosen packet out of a larger number of packets sent to packet allocation  306 . For example, only 1 out of every 128 packets sent to packet allocation  306  may also be sent to packet checks  350  for checking. Packet checks  350  may perform one or more checks that are normally performed by the network, transport and/or application layers. For example, packet checks  350  may perform tests that include, but are not limited to: expected packet length; expected payload type; correct IP protocol; correct UDP protocol; correct IP address; and correct Real-time Transport Protocol (RTP) version in header. 
     If packet checks  350  determines there may be a problem, it may indicate that packets being received by a particular session or recording stream need to be rejected. For example, packet checks  350  may determine that session # 2   312  is recording an error condition. In an example, an embodiment may indicate to packet storage  310  that it should stop recording session # 2   312 . In another example, packet tests may determine that a Denial of Service attack (DoS) is being directed against UDP destination port # 2 . In this example, an embodiment may direct one or more of network subset layer  304  and packet allocation  306  to stop processing or allocating packets directed to UDP destination port # 2 . In an embodiment, stopping the processing and/or allocating of packets directed to a UDP port would also stop the recording of a session associated with that UDP port. In another example, an alarm, such as an SNMP trap, may be raised to alert the system administrator and/or automated monitoring tools that packet checks  350  has determined there may be a problem. 
     Packet pool  352  sends packets to network subset layer  304  for transmission on network  320 . Packet pool  352  includes packets that have been preformatted for transmission. These preformatted packets may be complete IP-type packets including header and data portions that are static and not changed over a relatively long period of time. As each packet is prepared for transmission, some number of fields, such as RTP sequence number, timestamp, and any checksum fields, will still have to be set prior to transmission. However, the bulk of the effort, in creating, filling and subsequently destroying the packet object is eliminated by the use and reuse of a pool of pre-prepared packets. These packets may be, for example, IP-type packets further including RTP packets that include VoIP call data for silence, or a beep tone. This way, recording computer  340  may transmit silence, or a beep tone, without doing any extra processing to create those packets. 
     Recording computer  340  may need to transmit silence, or a beep tone, periodically as part of the process of recording computer communications, or to comply with regulatory requirements. For example, if recording computer  340  is participating in a VoIP call as a conference call participant, then recording computer  340  may need to send VoIP packets filled with silence to the conference bridge so that the conference bridge does not drop recording computer  340  from the conference call thereby ending recording computer  340 &#39;s ability to record in spite of the fact that the conference call was not over. 
     Transmit packets may only be formatted once, thus saving machine cycles or other resources on recording computer  340  that would otherwise be spent repeatedly formatting the same transmit packets. For example, for a beep-tone, a set of N (where N is an arbitrary number of packets) packets is typically needed. By repeating these cyclically, a repeating tone is played without the need for continually allocating, filling and releasing packets. In another example, there may still be a need to set the destination address, sequence number and/or timestamp on each packet prior to transmission, but this can be done in place on a small number of pre-filled packets that are reused over and over. This also removes the need for packet objects to be created and destroyed. 
     Packet allocation  306  receives packets from network subset layer  304 . Packet allocation  306  may be part of a transport layer, or may be implemented separately. In an embodiment, packet allocation  306  may accomplish the function of allocating packets passed to it by the network layer by examining the value at a fixed location, or offset, in each packet and using that value as a basis to identify a session. 
     In an embodiment, if the packet is formatted as a User Datagram Packet (UDP), then the value at the fixed location may be, for example, the destination port number of the packet. In an embodiment, packet allocation  306  may allocate packets based upon the destination port number of the packet. For example, packet allocation  306  may allocate a packet to session # 1   311  when the destination port number of the packet is 1. Packet allocation  306  may also allocate a packet to session # 2   312  when the destination port number of the packet is 2. This function may also be used with arbitrary port number-session number pairings such as allocating packets with a destination port number of 73 to session #N  313  where “#N” is an arbitrary identifier of the session these packets are to be associated with such as 99, or “VoIP call between 970-555-3234 and 408-555-9876 from 11:05 to 13:07 on Oct. 9, 2007”, or email “message-ID=14432593.1191958317010.” Once packets are allocated to a session, they are stored in packet storage  310  and associated with the one of sessions  311 - 313  to which they were allocated. 
     Packets may be allocated to a recording stream and sent to packet storage  310  without further processing by the transport or application layers, thus saving machine cycles or other resources on recording computer  340 . In an embodiment, the allocated packets may be subsequently ordered, duplicates removed, gaps filled and/or payload extracted prior to storage. This may be done so that what is stored is a better approximation to the payload of the stream of RTP packets. In addition, only a subset of all packets arriving may be checked for errors, thus saving machine cycles or other resources on recording computer  340 . These machine cycles and resources are saved by not subjecting the packets sent to packet allocation  106  to all of the examination normally undertaken by a full network layer. 
     The assumption that all IP packets received will be for a single IP address and/or that only UDP packets will be received allow the elimination of at least tests on the IP address and IP protocol type fields respectively. Similarly, recording computer  140  may be configured to rely upon the checksum of the data link layer to ensure the integrity of a transmission. This avoids testing the various checksums within the IP elements of the message. Testing for a valid RTP header may also be skipped as well as confirming that the packet length is consistent with the IP length indication. 
     Packet storage  310  is a storage medium such as a high capacity digital data storage device such as a CD-ROM, magnetic hard drive, DVD drive, DAT cassette, flash memory, or some combination of similar devices. Packet storage  310  may also store other information associated with the stored packets, or sessions  311 - 313 , such as the associations between stored packets and sessions  311 - 313  so that the computer communications recorded by recording computer  340  may be reconstructed, replayed, displayed, etc. 
       FIG. 4  is an illustration of a value at fixed position within a packet that may be used to allocate packets. The value at the fixed position may be used as a session identifier. A data link layer packet  401  includes frame header  410 , frame data  412 , and frame footer  414 . Frame data  412  may be formatted as network layer packet  402 . Network layer packet  402  may be comprised of fixed length IP header  420  and IP data  422 . IP data  422  may be formatted as transport layer packet  403 . Transport layer packet  403  may be formatted as fixed length UDP header  430  and UDP data  432 . UDP header  430  may be further divided into source port field  432 , destination port field  434 , length field  436 , and checksum field  438 . Each of these fields may be of a fixed length. 
     In this example, since IP header  420 , UDP header  430 , and source port field  432  are all of a fixed length, UDP destination port field  434  may be read directly from any of frame data  412 , IP packet, or UDP packet by examining the data that is at a fixed location, or fixed offset, in frame data  412 , IP packet, or UDP packet, respectively. In other words, if it is assumed that the only type of packet that is being processed is a UDP packet, the UDP destination port number can be read directly from an IP packet by examining a fixed location in the IP packet without further processing. This UDP destination port number can then be used as a session identifier to allocate the packet to a session. Accordingly, this allocation may be accomplished directly from an IP packet without the additional processing that is typically done by the network and transport layers prior to extracting the UDP destination port. 
       FIG. 5  is a flow diagram illustrating a method of resisting packet errors or service disruption attacks. In step  502 , an IP packet is received. In an embodiment, this packet is a subset of the packets received or processed by a network subset layer of a TCP/IP stack. For example, this method may only receive a copy of one arbitrarily chosen packet out of a larger number of packets received. For example, only 1 out of every 128 packets received by a network subset layer of a TCP/IP stack be received for checking. In step  504 , checks are performed on the received packet. These checks may be one or more checks that are normally performed by the network, transport and/or application layers. For example, these tests may include, but are not limited to: expected packet length; expected payload type; correct IP protocol; correct UDP protocol; correct IP address; and correct RTP version in header. 
     In step  508 , if step  504  determined there may be a problem, then it may indicate that packets being received by a particular session or recording stream need to be rejected. For example, step  504  may determine that session # 2   312  is recording an error condition. In this example, an embodiment of step  508  may indicate to packet storage  310  that it should stop recording session # 2   312 . In another example, step  504  may determine that a DoS attack is being directed against UDP destination port # 2 . In this example, an embodiment of step  508  may direct one or more of network subset layer  304  and packet allocation  306  to stop processing or allocating packets directed to UDP destination port # 2 . In an embodiment, stopping the processing and/or allocating of packets directed to a UDP port would also stop the recording of a session associated with that UDP port. In another example, an alarm, such as an SNMP trap, may be raised to alert the system administrator and/or automated monitoring tools that packet checks  350  has determined there may be a problem. 
       FIG. 6  is a flow diagram illustrating a method of providing packets suitable for transmission by a recording computer. In step  602 , a block of packets is formatted for transmission. These preformatted packets may be complete IP-type packets including header and data portions that are static and not changed over a relatively long period of time. As each packet is prepared for transmission, some number of fields, such as RTP sequence number, timestamp, and any checksum fields, will still have to be set prior to transmission. However, the bulk of the effort, in creating, filling and subsequently destroying the packet object is eliminated by the use and reuse of a pool of pre-prepared packets. These packets may be, for example, IP-type packets further including RTP packets that include VoIP call data for silence, or a beep tone. In step  604 , the method waits for the time to transmit. 
     In step  606 , the preformatted block of transmit packets is transmitted at predetermined intervals. The block of packets is not changed or otherwise processed between predetermined intervals, thus avoiding any steps or processing of the preformatted packets. Using this method, recording computer  340  may transmit silence, or a beep tone, without doing any extra processing to create those packets. Recording computer  340  may need to transmit silence, or a beep tone, periodically as part of the process of recording computer communications or to comply with regulatory requirements. For example, if recording computer  340  is participating in a VoIP call as a conference call participant, then recording computer  340  may need to send VoIP packets filled with silence to the conference bridge so that the conference bridge does not drop recording computer  340  from the conference call thereby ending recording computer&#39;s ability to record in spite of the fact that the conference call was not over. This method allows recording computer  340  to accomplish the transmission of silence or a beep tone with less processing. 
     Computers  130 ,  131 ,  330 ,  331 , and recording computers  140  and  340  may all be computer systems or contain computer systems. These computer systems are illustrated, by way of example, in  FIG. 7 . 
       FIG. 7  illustrates a block diagram of a computer system. Computer system  700  includes communication interface  720 , processing system  730 , and user interface  760 . Processing system  730  includes storage system  740 . Storage system  740  stores software  750 . Processing system  730  is linked to communication interface  720  and user interface  760 . Computer system  700  could be comprised of a programmed general-purpose computer, although those skilled in the art will appreciate that programmable or special purpose circuitry and equipment may be used. Computer system  700  may be distributed among multiple devices that together comprise elements  720 - 760 . 
     Communication interface  720  could comprise a network interface, modem, port, transceiver, or some other communication device. Communication interface  720  may be distributed among multiple communication devices. Processing system  730  could comprise a computer microprocessor, logic circuit, or some other processing device. Processing system  730  may be distributed among multiple processing devices. User interface  760  could comprise a keyboard, mouse, voice recognition interface, microphone and speakers, graphical display, touch screen, or some other type of user device. User interface  760  may be distributed among multiple user devices. Storage system  740  could comprise a disk, tape, integrated circuit, server, or some other memory device. Storage system  740  may be distributed among multiple memory devices. 
     Processing system  730  retrieves and executes software  750  from storage system  740 . Software  750  may comprise an operating system, utilities, drivers, networking software, and other software typically loaded onto a computer system. Software  750  could comprise an application program, firmware, or some other form of machine-readable processing instructions. When executed by processing system  730 , software  750  directs processing system  730  to operate as described herein. 
     The above description and associated figures teach the best mode of the invention. The following claims specify the scope of the invention. Note that some aspects of the best mode may not fall within the scope of the invention as specified by the claims. Those skilled in the art will appreciate that the features described above can be combined in various ways to form multiple variations of the invention. As a result, the invention is not limited to the specific embodiments described above but only by the following claims and their equivalents.