WO2008104128A1 - Procédé, système et dispositif permettant de réaliser une transmission de traduction d'adresse de réseau - Google Patents

Procédé, système et dispositif permettant de réaliser une transmission de traduction d'adresse de réseau Download PDF

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Publication number
WO2008104128A1
WO2008104128A1 PCT/CN2008/070348 CN2008070348W WO2008104128A1 WO 2008104128 A1 WO2008104128 A1 WO 2008104128A1 CN 2008070348 W CN2008070348 W CN 2008070348W WO 2008104128 A1 WO2008104128 A1 WO 2008104128A1
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WO
WIPO (PCT)
Prior art keywords
mgw
keep
candidate
mgc
candidate information
Prior art date
Application number
PCT/CN2008/070348
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English (en)
French (fr)
Inventor
Ning Zhu
Original Assignee
Huawei Technologies Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Huawei Technologies Co., Ltd. filed Critical Huawei Technologies Co., Ltd.
Priority to EP08715085.0A priority Critical patent/EP2117190B1/en
Priority to ES08715085T priority patent/ES2708089T3/es
Publication of WO2008104128A1 publication Critical patent/WO2008104128A1/zh
Priority to US12/501,266 priority patent/US8325741B2/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L61/00—Network arrangements, protocols or services for addressing or naming
    • H04L61/09—Mapping addresses
    • H04L61/25—Mapping addresses of the same type
    • H04L61/2503—Translation of Internet protocol [IP] addresses
    • H04L61/256—NAT traversal
    • H04L61/2575—NAT traversal using address mapping retrieval, e.g. simple traversal of user datagram protocol through session traversal utilities for NAT [STUN]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L65/00—Network arrangements, protocols or services for supporting real-time applications in data packet communication
    • H04L65/10—Architectures or entities
    • H04L65/102—Gateways
    • H04L65/1023—Media gateways
    • H04L65/1026—Media gateways at the edge

Definitions

  • the present invention relates to next generation network technologies, and more particularly to a method, system and apparatus for implementing network address translation traversal in a next generation network.
  • Next Generation Network is a Public Switched Telephone Network (PSTN) based on Time Division Multiplex (TDM) and Internet Protocol/Asynchronous Transfer Mode (IP, Internet Protocol/ATM).
  • PSTN Public Switched Telephone Network
  • TDM Time Division Multiplex
  • IP Internet Protocol/ATM
  • Asynchronous Transfer Mode is a product of the convergence of packet networks, which makes it possible to realize integrated services of voice, video and data on the same network, marking the arrival of the new generation of telecommunications networks.
  • FIG. 1 is a schematic diagram of the structure of an existing NGN network.
  • the NGN network mainly includes a media gateway (MGW, Media Gateway) and a media gateway controller (MGC).
  • MGW media gateway controller
  • the MGC is configured to implement call state management and control of MGW bearer resources.
  • the MGW is configured to convert the media stream type from one format to another format, for example, to place an E1 time slot in the circuit switched network. It is converted into a real time transport protocol (RTP) media stream in an IP network, and media stream is established, modified, released, and resource managed under the control of the MGC.
  • RTP real time transport protocol
  • the bearer network where the MGW1 and the MGW2 are located is the same private network or the public network, the IP packets of the MGW1 and the MGW2 during the information exchange process can be directly sent to the other party.
  • MGW1 and MGW2 are in different bearer networks, for example, MGW1 is in the public network and MGW2 is in the private network, or both MGW1 and MGW2 are in the private network, but the two networks cannot directly send IP packets.
  • MGW1 and MGW2 are in different bearer networks, for example, MGW1 is in the public network and MGW2 is in the private network, or both MGW1 and MGW2 are in the private network, but the two networks cannot directly send IP packets.
  • the media stream is tuned or not.
  • the same problem may exist in the case where one end of the media stream is an MGW, and the other end is a Session Initiation Protocol (SIP) terminal, an H323 terminal, a circuit domain network terminal, or a packet network terminal.
  • NAT Network Address Translation
  • IP Internet Protocol
  • NAT Network Address Translation
  • IP Internet Protocol
  • NAT allows an organization-specific intranet, that is, a terminal in a private network to transparently connect to a public domain, that is, a terminal in a public network, and the internal terminal does not need to have a registered Internet address.
  • the NAT traversal technology uses a private IP address for the terminal on the private network and accesses the public network through the exported NAT/firewall (FW, Fire Wall).
  • the two commonly used NAT traversal methods are User Datagram Protocol (UDP), Simple Traversal of UDP Through Network Address Translator (STUN), and Trunk Traversal NAT (TURN, Traversal Using). Relay NAT) method.
  • the STUN method is implemented as follows:
  • the STUN client (CLIENT) sends a request STUN message to the STUN server (SERVER) outside the NAT through UDP.
  • the STUN SERVER After receiving the request message, the STUN SERVER generates a response message, and the response message carries the sending request.
  • the source port of the message that is, the external interface information corresponding to the STUN CLIENT on the NAT;
  • the STUN SERVER sends the response message to the STUN CLIENT through the NAT;
  • the STUN CLIENT knows the external address of the NAT through the response message, and fills in the external address.
  • To the UDP payload of the call protocol to inform the receiving end of the RTP receiving address of the local end and the port number is the address and port number outside the NAT.
  • the voice over IP (VoIP) terminal in the private network knows the service address of the public network in advance, and fills the service address into the IP packet payload, that is, the address information of the signaling.
  • VoIP voice over IP
  • the address in the local session description protocol (SDP) of the RTP1 in the private network is the private network address, which is assumed to be the Customer Premises Equipment (CPE).
  • the MGC specifies that the remote address of the RTP endpoint RTP2 of the MGW2 is CPE2 in the H.248 message sent to the MGW2 in the public network.
  • the RTP2 will subsequently send the media stream to the MGW1.
  • the media stream is sent to the address of CPE2.
  • CPE2 is a private network address, and the media stream from RTP2 is unreachable.
  • NAT will convert its address CPE2 to CPE1 and add it to H.248.37.
  • a packet signal carrying the address CPE1 information is sent to the RTP2 to indicate that the RTP2 is NAT traversed.
  • RTP2 replaces the original remote private network address CPE2 with the received address CPE1, and sends the subsequent media stream to CPE1.
  • the NAT sends the media stream received by the CPE1 to the private network address CPE2 of the MGW1 according to the pre-established address mapping relationship.
  • the NAT traversal packet defined in H.248.37 requires the endpoint in the private network to first send the media stream to the endpoint in the public network in order to trigger the NAT to generate the address mapping, and the endpoint on the public network will receive the media stream.
  • the source address is the destination address of the sending media stream.
  • the embodiment of the invention provides a method for implementing network address translation traversal, which can improve the stability of media stream transmission.
  • the embodiment of the invention provides a system for implementing network address translation traversal, which can improve the stability of media stream transmission.
  • the embodiments of the present invention provide a device for implementing network address translation traversal, which can improve the stability of media stream transmission.
  • a method for implementing network address translation traversal comprising:
  • the first media gateway MGW obtains the candidate information of the local end and the opposite end to establish the ICE mechanism support device, and sends the local candidate information to the ICE mechanism support device; the first MGW according to the candidate information and the The ICE mechanism supports the device for conducting detection; the delivery of body fluid.
  • a system for implementing NAT traversal comprising: a first MGW and an ICE mechanism support device;
  • the first MGW is configured to obtain candidate information of the local end and the peer ICE mechanism supporting device, perform conduction detection according to the candidate information and the ICE mechanism supporting device, and perform a conduction detection result according to the ICE mechanism.
  • the ICE mechanism supporting device is configured to acquire candidate information of the first MGW of the local end and the opposite end, perform conduction detection with the first MGW according to the candidate information, and perform a continuity check according to the candidate information.
  • the measurement result is transmitted to the first MGW by the media stream.
  • a device for implementing network address translation NAT traversing comprising: an acquiring unit, a conduction detecting unit, and a transmitting unit;
  • the obtaining unit is configured to obtain candidate information of the local end and the peer ICE mechanism supporting device, and send the local terminal candidate information to the ICE mechanism supporting device;
  • the continuity detecting unit is configured to perform continuity detection with the ICE mechanism supporting device according to the candidate information
  • the transmitting unit is configured to perform media stream transmission with the ICE mechanism supporting device according to the continuity detection result.
  • a device for implementing network address translation traversal comprising: a control unit and a first sending unit;
  • the control unit is configured to control the first MGW to obtain local candidate information
  • the first sending unit is configured to perform signaling interaction with the ICE mechanism supporting device, to obtain candidate information of the ICE mechanism supporting device, and send the candidate information to the first MGW, and send the candidate information of the first MGW to the
  • the ICE mechanism supports the device.
  • the GW mechanism in the MGW and the network support device performs conduction detection according to the obtained candidate information of both parties, and performs NAT traversal of the media stream according to the result of the continuity detection.
  • the solution in the embodiment of the present invention does not need the endpoint in the private network to send the media stream to the NAT in advance to trigger the NAT to generate the mapping address, and solves the NAT traversal problem in the private network at both ends of the media stream.
  • the MGW can not only implement the NAT flow traversal of the media stream NAT with other MGWs supporting the function of the present invention, thereby improving the stability of media stream transmission in the network including the MGC and the MGW such as NGN.
  • FIG. 1 is a schematic structural diagram of an NGN network in the prior art
  • FIG. 2 is a schematic structural diagram of a system embodiment of the present invention.
  • FIG. 3 is a schematic structural view of an embodiment of a system of the present invention.
  • FIG. 4 is a schematic structural view of another embodiment of the system of the present invention.
  • FIG. 5 is a schematic structural diagram of an embodiment of an apparatus according to the present invention.
  • FIG. 6 is a flow chart of an embodiment of a method of the present invention.
  • the NGN network in the prior art implements NAT traversal, there is a defect that the stability of the media stream transmission cannot be ensured. Therefore, in the embodiment of the present invention, it is desirable to propose a NAT traversal mode different from the prior art to improve NGN, etc.
  • the embodiment of the present invention adopts an ICE (Interactive Connectivity Establishment) mechanism, which can better solve the SIP-based NAT traversal problem by implementing the NAT traversal method such as STUN and TURN.
  • a candidate list is generated by STUN or TURN at the transmitting and receiving ends of the media stream, and the candidate lists at both ends are cross-paired to generate a series of candidate pairs, each of which includes a local candidate and a remote candidate; then conduct a Connectivity Check and decision for each candidate pair (Concluding ICE), the candidate pair with the highest priority among the candidate pairs with the successful detection of the continuity detection is selected as the channel for transmitting and receiving the media stream at both ends of the media stream.
  • ICE Interactive Connectivity Establishment
  • the specific implementation process of the ICE mechanism is as follows: Assume that the SIP terminal at the calling end allocates a host (host) address for a certain media stream, assuming that the address is ho. Before sending an offer message, ho obtains a mapped public network address through the STUN method, which is called a server reflexive address in the ICE mechanism, assuming that the address is sro. In addition, ho also obtains a public network address through the TURN method, which is called a relay address in the ICE mechanism, assuming that the address is ro. In this way, three candidate information are obtained at the calling end: a host candidate, a server reflexive candidate, and a relayed candidate. The three candidate information and the ⁇ J address are respectively ho.
  • the IP version of the address mentioned here may be IP V4 or IP V6.
  • the caller After the caller obtains three candidate information, it sends it to the called end through the offer message. After receiving the three candidate information of the peer, the called end obtains its candidate information in the same way as the peer. Assume that three candidate information are also obtained, which are the host candidate of the called end, server reflexive Candidate and relayed candidate, the corresponding addresses are ha, sra and ra. The called party sends these three candidate information to the calling end through a reply (answer) message.
  • the candidate information at both ends is cross-combined to form 9 candidate pairs (the actual situation may not have so many candidate pairs, for example, there are only two candidates on the calling side and only one candidate on the called side), and each candidate pair may form a valid one. Media stream channel.
  • the calling and called terminals test the nine candidate pairs according to the priority order through the mechanism of continuity detection.
  • the specific test method is that the calling end sends a STUN binding request message to the called end, and after receiving the STUN binding request message, the called end sends a response message to the calling end; for the same candidate pair, the called party
  • the terminal sends a STUN binding request message to the calling end, and the calling end also sends back a response message. In this way, the continuity detection for a candidate pair is completed.
  • the process includes two request messages and two response messages, it can be called It is a 4-message handshake.
  • the calling end and the called end can perform media stream transmission and reception according to the IP address and port represented by the candidate pair.
  • the ICE mechanism is introduced into the functions of the MGC and the MGW, and the implementation manner is: the first MGW and the ICE mechanism Supporting devices (ie, devices capable of supporting the ICE mechanism) acquire candidate information of the local end and the opposite end; the first MGW and ICE mechanism support device performs conduction detection according to the candidate information; the first MGW and the ICE mechanism support device perform according to the continuity detection result The transmission of the media stream.
  • the first MGW and the ICE mechanism Supporting devices ie, devices capable of supporting the ICE mechanism
  • the first MGW and ICE mechanism support device performs conduction detection according to the candidate information
  • the first MGW and the ICE mechanism support device perform according to the continuity detection result The transmission of the media stream.
  • FIG. 2 is a schematic structural diagram of a system embodiment of the present invention.
  • the composition of the system of the present invention includes: a first MGW, an ICE mechanism support device, and a first MGC;
  • the first MGW is configured to obtain the local end candidate information under the control of the first MGC, and receive the candidate information of the peer ICE mechanism supporting device sent by the first MGC, and perform the continuity detection with the peer ICE mechanism supporting device, The continuity detection result is reported to the first MGC, and the media stream is transmitted according to the continuity detection result;
  • the ICE mechanism support device is configured to perform signaling interaction with the first MGC, receive the candidate information of the first MGW sent by the first MGC, obtain the candidate information of the local end, and send the local candidate information to the first MGC, and The first MGW performs the continuity detection, performs the media stream transmission according to the continuity detection result, and notifies the first MGC when the (In-Use) candidate pair is updated;
  • the first MGC is configured to control the first MGW to obtain the local candidate information, and perform signaling interaction with the ICE mechanism support device to obtain candidate information of the ICE mechanism support device and send the information to the first MGW, and select the candidate information of the first MGW.
  • the mechanism support device receives the In-Use candidate pair from the ICE mechanism support device, and the first MGC is further configured to send the keep-alive message type and/or the keep-alive message sending period setting message to the first MGW.
  • the first MGW is further configured to: receive a keep-alive message type and/or a keep-alive message sending period setting message from the first MGC, and further use, according to the keep-alive message, the first MGC, to send to the first MGW
  • the first MGW is further configured to: receive the keep-alive message sending indication from the first MGC, and send the keep-alive message to the ICE mechanism support device after receiving the keep-alive message sending indication .
  • the ICE mechanism supporting device may be a second MGW controlled by the first MGC, or a combination of the second MGW and the second MGC, or a SIP proxy supporting the ICE mechanism, or an IMS network supporting the ICE mechanism. .
  • FIG. 3 is a schematic structural diagram of an embodiment of the system according to the present invention.
  • the ICE mechanism supporting device is a combination of the second MGC 203 and the second MGW 204, where the second MGW 204 is configured to receive the peer end from the second MGC 203.
  • the candidate information of the MGW 202, and the Gathering Candidates indication from the second MGC 203, the local candidate information is obtained by the STUN or the like according to the candidate collection indication, and sent to the second MGC 203;
  • the first MGW 202 performs conduction detection; and performs media stream transmission between the first MGW 202 and the first MGW 202 according to the continuity detection result;
  • the second MGC 203 is configured to receive candidate information of the first MGW 202 from the first MGC 201, send a candidate collection indication to the second MGW 204, send the candidate information of the second MGW 204 to the first MGC 201, and receive the continuity detection from the second MGW 204. result.
  • the candidate collection indication may not be used, but the MGW is automatically collected to report the candidate information when the RTP endpoint is allocated in the media capability negotiation process. If the result of the continuity test is different from the previous In-Use candidate, the MGC can pass The modify (modify) message updates the SDP of the RTP endpoint on the local MGW, and can also notify the peer through the SIP Updated Offer message. After receiving the Updated Offer message sent by the peer end, the MGC can update the SDP of the RTP endpoint on the local MGW through the modify message.
  • the first MGC 201 and the first MGW 202 are respectively represented by MGC1 202 and MGW1 201; the second MGC 203 and the second MGW 204 are respectively represented by MGC 2 203 and MGW 2 204, as shown in FIG. 3, assuming MGW1 202 is in the private network, and MGW2 204 is in the public network.
  • the workflow of the system is:
  • the MGW1 202 initiates a call, and the MGC1 201 establishes an RTP endpoint RTP1 on the MGW1 202.
  • the MGW1 202 acquires candidate information under the control of the MGC1 201, including host candidate information, server reflection candidate information, and broadcast candidate.
  • the information is sent to the MGC 1 201 through the H.248 protocol.
  • the MGC1 201 transmits the candidate information to the MGC 2 203 that controls the MGW 2 204 in the public network through the SIP protocol, and the MGC 2 203 further transmits the candidate information to the MGW 2 204.
  • the MGW2 204 After receiving the candidate information of the MGW1 202, the MGW2 204 obtains its own candidate information in the same manner as the MGW1 202. In this embodiment, the candidate information of the MGW2 204 requires only one host candidate information because it is in the public network. The MGW 2 204 transmits the host candidate information to the MGW 1 202 through the MGC 2 203 and the MGC 1 201. In this way, the MGWs at both ends know the candidate list of the local end and the opposite end. Then, MGW1 202 and MGW2 204 initiate a conduction detection process under the direction of the respective MGCs or automatically. For example, after receiving the candidate information of the MGW2 204, the MGW1 202 can automatically initiate the continuity detection.
  • the specific continuity detection process is the same as the prior art, that is, according to the standard of the ICE mechanism.
  • the MGC1 201 and the MGC2 203 need to indicate whether the corresponding MGW is a control role, and the final candidate pair is selected by the control role.
  • MGC1 201 and MGC2 203 also need to indicate whether the corresponding MGW is a session initiator, and the information is calculated in the candidate pair priority.
  • the indication may be an H.248 attribute, or an H.248 signal, or a parameter of an event, or may be set by a rule, for example: If there is no remote SDP when adding an RTP endpoint, the call is The initiator, otherwise the answerer.
  • the continuity detection is completed.
  • the MGW1 202 and the MGW2 204 report the conduction detection result to the MGC1 201 and/or the MGC2 203.
  • the MGW1 202 and the MGW2 204 can perform media stream transmission according to the continuity detection result.
  • the SDP content needs to be updated.
  • ICE mechanism has the concept of Lite Implementation.
  • the end of lightweight execution does not need to collect candidates. This situation can be understood as only one host candidate.
  • connection mode and the implemented functions of the NAT and the STUN server shown in FIG. 3 are the same as those in the prior art, and are not described again.
  • the MGW2 204 and the MGW1 202 may be controlled by the same MGC, and the function of the MGW2 204 is the same as that of the MGW1 202, that is, for receiving candidate information about the first MGW 202 from the first MGC 201, and acquiring The local end candidate information is sent to the first MGC 201, and performs the continuity detection with the first MGW 202 according to the local end and the peer candidate information.
  • FIG. 4 is a schematic structural view of another embodiment of the system of the present invention. As shown in FIG. 4, the difference between the embodiment and the first embodiment is that the MGW2 204 and the MGC2 203 in the first embodiment are replaced by the SIP terminal 303 in this embodiment. The working mode and implementation of the system in this embodiment There is no essential difference between the first and the second, and will not be repeated.
  • FIG. 5 is a schematic structural diagram of an embodiment of an apparatus according to the present invention.
  • the device includes: an obtaining unit 501, a turn-on detecting unit 502, and a transmitting unit 503;
  • the obtaining unit 501 is configured to obtain candidate information of the local end and the peer ICE mechanism supporting device, and send the local terminal candidate information to the ICE mechanism supporting device.
  • the ping detection unit 502 is configured to perform continuity detection with the ICE mechanism support device according to the candidate information.
  • the transmitting unit 503 is configured to perform media stream transmission with the ICE mechanism supporting device according to the continuity detection result.
  • the device further includes: a receiving unit 504, configured to receive a candidate collection indication or a continuity detection initiation indication from the MGC; the obtaining unit acquires the local candidate information according to the candidate collection indication; and the conduction detection unit initiates the indication according to the continuity detection. Initiating a conduction check with the ICE mechanism support device.
  • the device may further include: a reporting unit 505, configured to report the continuity detection result to the MGC; and a keep-alive message sending unit 506, configured to receive the keep-alive message type and/or the keep-alive message from the MGC.
  • the message sending period setting message sends a keep-alive message to the ICE mechanism supporting device according to the keep-alive message type and/or the keep-alive message sending period; or, receives the keep-alive message sending instruction from the MGC, and follows the indication to the ICE mechanism.
  • the device is enabled to send keep-alive messages.
  • the foregoing MGC may specifically include: a control unit and a first sending unit;
  • control unit configured to control the first MGW to obtain local end candidate information
  • a first sending unit configured to perform signaling interaction with the ICE mechanism supporting device, to obtain candidate information of the ICE mechanism supporting device, and send the information to the first MGW,
  • a candidate information of the MGW is sent to the ICE mechanism support device.
  • the MGC can further include:
  • a second sending unit configured to send a candidate collection indication to the first MGW, to instruct the first MGW to obtain the candidate information of the local end;
  • a third sending unit configured to send a continuity detection initiation indication to the first MGW
  • a fourth sending unit configured to send, to the first MGW, whether the first MGW is the indication information of the control role, or send, to the first MGW, whether the first MGW is the indication information of the session initiator;
  • a fifth sending unit configured to send a keep-alive message type and/or a keep-alive message sending period setting message to the first MGW, to indicate that the first MGW sends the keep-alive message type and/or the keep-alive message according to the keep-alive message type and/or the keep-alive message
  • the period sends a keep-alive message to the ICE mechanism support device, or is configured to send a keep-alive message sending indication to the first MGW, to instruct the first MGW to send the keep-alive message to the ICE mechanism support device according to the indication.
  • FIG. 6 is a flowchart of an embodiment of a method according to the present invention. As shown in FIG. 6, the method includes the following steps: Step 601: The first MGW and the ICE mechanism support device obtain candidate information of the local end and the opposite end.
  • the first MGW and the ICE support device need to obtain the candidate information of the local end and the peer end.
  • the specific acquisition mode is as follows:
  • the first MGW obtains the local candidate information, and sends the local candidate information to the peer ICE mechanism support device by using the first MGC; the peer ICE mechanism supports the device to obtain the local candidate information, and uses the first MGC to obtain the local candidate information. Sending to the first MGW; or, the peer ICE mechanism supports the device to obtain the local candidate information, and sends the local candidate information to the first MGW through the first MGC; the first MGW obtains the local candidate information, and passes the first MGC.
  • the local candidate information is sent to the peer ICE mechanism support device.
  • This step is included in the media capability negotiation process at both ends of the session.
  • the two methods respectively correspond to the first MGW as the initiator of the session (the offer) and the first MGW as the responder (the answerer) of the session.
  • the execution of the process is not so strict.
  • the first MGC may not First MGW
  • the candidate information is notified to the peer ICE mechanism support device, that is, the offer message does not carry the SDP, but after the peer ICE mechanism supports the device to bring back the candidate information of the peer through the SDP in the answer message, the first MGC re-enters the local end
  • the candidate information is sent to the peer. Therefore, the essence of the step is: in the media capability negotiation phase of the session, the two ends respectively collect the local candidate information and exchange the candidate information with the peer through signaling, such as H.248 or SIP, and the specific implementation process thereof It may be flexible.
  • the first MGW may further include: sending, by the first MGC, a candidate collection indication to the first MGW; and correspondingly, the first MGW, after receiving the candidate collection indication, acquiring the local candidate information.
  • the manner in which the first MGC sends the candidate collection indication to the first MGW is: The first MGC sends the candidate collection indication to the first MGW by using the extended SDP.
  • the manner in which the first MGC and ICE mechanisms support the device to obtain the respective candidate information is the same as the manner in which the SIP terminal acquires the candidate information in the prior art ICE mechanism.
  • the foregoing ICE mechanism supporting device may be a second MGW, a combination of the second MGW and the second MGC, or a SIP agent supporting the ICE mechanism.
  • the manner in which the ICE mechanism supports the device to obtain the local candidate information is: the second MGC receives the candidate information about the first MGW from the first MGC, and the The candidate information is sent to the second MGW; the second MGW creates an RTP endpoint, and obtains the local candidate information under the instruction of the second MGC.
  • the ICE mechanism supports the device as a SIP terminal, the ICE mechanism supports the device to obtain the local candidate information in the following manner: After receiving the candidate information of the first MGW, the SIP terminal automatically obtains the candidate information of the local end.
  • the call flow may not be initiated by the MG mechanism supported by the peer.
  • the first MGW and the ICE mechanism support the device to obtain the local candidate information and acquire the pair.
  • the order of candidate information may also There are multiple arrangements, which are related to the specific process.
  • Step 602 The first MGW and the ICE mechanism support device perform continuity detection according to the candidate information.
  • the first MGW and the ICE mechanism support device can perform the continuity detection to determine the candidate pair finally used for transmitting the media stream.
  • the first MGW and/or the ICE mechanism supporting device may automatically initiate the conduction detection, or may initiate the conduction detection under the control of the first MGC.
  • the .248 protocol sends a continuity detection initiation indication to the first MGW, and/or indication information indicating whether the first MGW is a control role, and/or whether the local end is the indication information of the session initiator.
  • the control role indication information is used to indicate whether the first MGW is a control role, and the final candidate pair selection is performed by the control role.
  • the session initiator indication information is used to indicate that the priority level of the candidate pair is calculated by the local end, and the indication may also be described above. If the H.248 message in the media negotiation process carries a remote SDP, the first MGW distinguishes whether it is the initiator of the session. If it is automatically initiated conduction detection, both ends can initiate the conduction detection process after obtaining the candidate information.
  • the first MGW reports the conduction detection result to the first MGC by means of an event report or a response to the H.248 request message according to the event setting on the first MGC; the reporting timing may be After the completion of the detection, it may also be after the failure of the conduction detection.
  • Step 603 The first MGW and the ICE mechanism support the device to perform media stream transmission according to the continuity detection result.
  • the first MGW and the ICE mechanism support device performs the media stream transmission according to the continuity detection result obtained in step 602.
  • the first MGW and ICE mechanism support device may not continuously send and receive media streams, that is, there may be no media stream transmission in the network for a certain period of time. In this case, to maintain channel validity.
  • the first MGW needs to send a keepalive message to the peer ICE mechanism support device, and may need to respond to the keepalive message sent by the peer ICE mechanism support device.
  • the keep-alive message may be a STUN binding request message that needs to be answered, or a no-operation (No-Op) packet or a mute packet that does not require a response.
  • No-Op no-operation
  • the transmission period of the keep-alive packet is smaller than the time that the address mapping on the NAT is maintained, and the keep-alive packet is transmitted along the path of the media stream.
  • the first MGC may send the keep-alive message type and/or the keep-alive message sending period setting message to the first MGW in advance by using the extended H.248 protocol; correspondingly, when the first MGW needs to send the keep-alive message, Sending a keep-alive message to the ICE mechanism support device according to the set keep-alive message type and/or the keep-alive message sending period; or, the first MGC sends the keep-alive message to the first MGW by using the extended H.248 protocol.
  • the first MGW After receiving the keep-alive message sending instruction of the first MGC, the first MGW sends a keep-alive message to the ICE mechanism supporting device.
  • the keep-alive message sending indication may also carry the keep-alive message type and/or the keep-alive message sending period information.
  • the candidate information mentioned in steps 601-603 is one or more of host candidate information, server reflection candidate information, and relay candidate information.
  • the continuity detection uses the STUN binding request message
  • the response of the message carries a reflexive address (the address in the embodiment of the present invention generally refers to an IP address and a port).
  • the address is different from the existing local candidate address
  • the reflected address is called the peer reflection address.
  • the difference between the address and the server reflection address is that the former is generated by the peer reflection, and the latter is reflected on the STUN server. Generated.
  • the source address of the STUN binding request message received in the continuity detection is different from all existing remote candidates, and the continuity detection is successful, it can be determined that this is a peer reflection far.
  • Peer reflexive remote candidate If the peer reflection candidate is selected as the candidate for media stream transmission, the address needs to be reported to the MGC for use in gating.
  • FIG. 7 is a flowchart of another embodiment of the method according to the present invention.
  • the system structure according to this embodiment is shown in FIG. 3, that is, the ICE mechanism supporting device is a combination of the second MGC and the second MGW.
  • the first MGC and the first MGW are respectively represented by MGC1 and MGW1; the second MGC and the second MGW are respectively represented by MGC2 and MGW2, and the method embodiment includes the following steps:
  • Step 701 MGW1 and MGC2 obtain candidate information of the local end and the opposite end.
  • the MGC1 side initiates a call, and establishes an RTP endpoint RTP1 in the media capability negotiation process.
  • the RTP endpoint has a local network interface address ho, ho may be an IPV4 address plus port, or may be an IPV6 address plus port, which is assumed in this embodiment. Add a port for the IPV4 address.
  • the MGW 1 obtains the server reflection candidate information sro and the relay candidate information ro through the STUN server.
  • the candidate information is obtained by the MGW1 by the MSG1 in the media stream negotiation process.
  • the first two “$” respectively indicate the server reflection address and port that MGW1 needs to report; the last two “$” respectively indicate the host address and port that MGW1 needs to report;
  • UDP means using the UDP protocol
  • port indicates the port that MGW1 needs to fill in.
  • MGW1 answers, it fills in the corresponding server reflection candidate address and port at the corresponding position of the SDP, as follows:
  • MGC1 obtains three candidate information of MGW1, and can specify one of the m/c lines set to the SDP as an in-use candidate; in the subsequent step 702, if the candidate information obtained by the continuity detection is in- If the candidate information stored in the Use candidate does not match, the MGC1 can replace the candidate information in the m/c line In-Use candidate with the candidate information obtained by the continuity detection.
  • MGC1 sends the three candidate information to MGC2 through SIP signaling, and sends it to MGW2 through MGC2. Similar to MGW1, RTP endpoint RTP2 is created on MGW2, and candidate information is obtained.
  • MGW2 Since MGW2 is in the public network, only one candidate information, that is, host candidate information ha, is needed, and the host candidate information is sent to MGW1 through MGC2 and MGC1. Thus, both MGW1 and MGW2 know the candidate information of the local end and the opposite end, that is, the candidate list, and form three candidate pairs, namely (ho, ha), (sro, ha), and (ro, ha).
  • Step 702 The MGW1 initiates the continuity detection, and reports the continuity detection result to the MGC1.
  • the MGC1 instructs the MGW1 to initiate the continuity detection, indicates whether the MGW1 is the control role, and indicates whether the MGW1 is the session initiator through the extended H.248 protocol.
  • the method of extending the H.248 protocol mentioned here may refer to newly defining an ostuncc package on the cornerstone of the original H.248 protocol, and the ostuncc package includes:
  • the signal sec is used to indicate that the MGW1 initiates the continuity detection of the ICE mechanism, and the signal specifically indicates the media stream to be tested for conduction, and further carries the indication parameter, such as the stream ID of the H.248, and the ICE mechanism.
  • the indication parameter such as the stream ID of the H.248, and the ICE mechanism.
  • One or more of the foundation number and the component-id information; or, instead of carrying these parameters, all the media streams within the range of the signal may be turned on.
  • the attribute control is used to indicate whether the MGW1 is a controlling role or a controlled role.
  • the attribute can be placed under a local control descriptor (Local Control Descriptor).
  • MGW1 is assumed to be a control role, that is, , MGW1 determines the candidate pair to be finally selected.
  • Attribute side Used to indicate whether the MGW1 side is the offer side or the answer end. This value is used for the priority calculation of the candidate pair.
  • the information carried by these two attributes can also be passed through the parameters of the sec signal.
  • Conduction detection is performed between the MGW1 and the MGW2, and the conduction detection result is reported to the MGC, and the control role and the controlled role, that is, the MGW1 and the MGW2 can be connected to the detection result, and the ICE mechanism specifies the status of the conduction detection.
  • the reporting time may be the completion of the continuity detection, or may be after the failure of the continuity detection;
  • the reporting manner may be an event reporting manner, or may be reported in the response of the H.248 request message;
  • the reported content may include the following One or more of the content:
  • the current status of each candidate pair such as: Waiting, In-Progress, Succeeded, Failed, or Frozen;
  • the selected candidate pair includes the peer reflection candidate (Peer Reflexive) Candidate), also need to report the type of peer reflection, that is, the local (local) peer reflection or the remote (remote) peer reflection, and the peer end reflection candidate IP address and port, the IP address And the port will be used for subsequent processing, such as gating.
  • the peer reflection candidate peer Reflexive
  • the MGW1 is responsible for reporting the continuity detection result, and the MGW1 also needs to extend the H.248 protocol to transmit the continuity detection result information, which can be implemented by defining an event ccr in the newly defined ostuncc packet.
  • the event can be set to report the continuity detection result of all media streams on an RTP endpoint, or the continuity detection result of all media streams on the specified streamID on the RTP endpoint.
  • the information carried in the event report includes the stream ID of the H.248, the group ID, the local foundation number, the peer foundation number, the component-id, the peer reflection type (local or remote), the peer's reflected IP address and port, and the reflection. IP address and port, and whether it is one or more of the selected candidate peer information.
  • the data type of the reported event parameter result is a list of strings in the following format:
  • streamID is the stream ID of H.248
  • Group ID is the group ID of H.248;
  • the foundation-L is the local base number of the candidate pair
  • the foundation-R is the peer base number of the candidate pair
  • the component-id is the component-id of the candidate pair.
  • the local and peer use the same component-id.
  • State is the current state of the selection, and the value is: Waiting, In- Progress, Succeeded, Failed or Frozen;
  • the peer reflexive type and address are types of peer reflection candidates.
  • the two types include local peer reflection candidates and remote peer reflection candidates. There may be only one end of a candidate pair A peer reflection candidate may be generated, or a peer reflection candidate may be generated at both ends.
  • the type of all the peer reflection candidates in the candidate pair and the corresponding peer reflection IP address and port can be reported by the peer Reflexive type and address.
  • Selected is used to identify whether the candidate pair is selected for transmitting the media stream.
  • the ICE mechanism standard stipulates that in a candidate pair, the two candidate component-ids must be the same. If the MGC performs special processing on the component-id, the component-id is not repeated in different groups and streams, for example. : The MGW does not need to report the streamID and groupID, but may need to report two different component-ids.
  • the continuity test fails, it can be represented by returning an error code or returning an empty string.
  • the content reported by the event may include some or all of the content reported by the above event.
  • the elected parameter may not be needed.
  • the reported message in order to prevent the reported message from being too long, it may be considered to report only candidate pairs of certain states, such as a successful detection and a failed candidate pair, and it is not necessary to report the candidate pair that is not detected, and may add a parameter in the event setting. Wait for the purpose.
  • Step 703 The MGW1 and the MGW2 perform media stream transmission according to the continuity detection result.
  • MGC1 and MGC2 update the SDP of MGW1 and MGW2 according to the reported continuity detection result, and ensure that the IP address and port in the m/c line are the selected candidate IP addresses and ports. It should be noted that this operation may be redundant because MGW1 and MGW2 have already obtained the selected candidate pairs during the continuity detection process, and the description here is mainly for alignment with the current ICE mechanism standard.
  • the MGW1 will send a keep-alive message to the MGW2 to maintain the validity of the candidate pair. This requires the MGC1 to pre-set the type of keep-alive message and/or the keep-alive message transmission period for the MGW1 through the extended H.248. After that, the MGW1 will set the keep-alive message when it needs to send the keep-alive message.
  • the MGC1 sends a keep-alive message transmission indication to the MGW1.
  • the MGW1 sends a keep-alive message to the MGW2 every time after receiving the keep-alive message transmission indication.
  • the calculation time of the keep-alive packet transmission period starts from the time when the media stream stops transmitting and receiving. If there is always a media stream, there is no need to send a keep-alive message. To do this, you need to add the following to the ostuncc package:
  • Attribute kaType Indicates the type of the keepalive message, such as the null-operated (No-Op) message, the mute message, and the STUN binding request message.
  • the first two types of packets are considered to not support STUN/.
  • the ICE device is protected by NAT before, so that it is not limited to the candidate pair information, and the live message is sent on the transmission path of the media stream, and the attribute can be placed under the LocalControlDescriptor;
  • Attribute Tr Used to indicate the transmission period of keep-alive text. This attribute can be set to set the Tr value separately for different media streams, or set all media streams. This attribute can be placed under LocalControlDescriptor.
  • the sending of the keep-alive message may also be implemented by means of a signal, which may specify a media stream path that needs to send a keep-alive message, or may indicate that the keep-alive message is sent on all media stream paths; You can also set the keepalive message type and Tr attribute by parameter.
  • the ostuncc package may further include an attribute iuType: a type for indicating the In-Use candidate mentioned in step 701.
  • the types of In-Use candidates include host candidate, server reflexive candidateh, and relayed candidate. These three types can be defined as he ( 0x0001 ), src ( 0x0002 ), and rc ( 0x0003 ), respectively. It can also be placed under LocalControlDescriptor.
  • the MGW puts the corresponding candidate type IP address and port into the SDP according to the attribute value. In the m/c line.
  • This embodiment describes the implementation process of the solution of the present invention when both ends of the media stream are both MGW.
  • MGW and other ICE mechanisms support the device to perform media stream interaction, the specific implementation process is similar to that shown in FIG. Those skilled in the art can easily introduce them, and will not be described here.
  • the GW mechanism in the MGW and the network support device performs conduction detection according to the obtained candidate information of both parties, and performs NAT traversal of the media stream according to the result of the continuity detection.
  • the solution in the embodiment of the present invention does not need the endpoint in the private network to send the media stream to the NAT in advance to trigger the NAT to generate the mapping address, and solves the NAT traversal problem in the private network at both ends of the media stream.
  • the MGW can not only implement the NAT flow traversal of the media stream NAT with other MGWs supporting the function of the present invention, thereby improving the stability of media stream transmission in the network including the MGC and the MGW such as NGN.

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Description

实现网络地址转换穿越的方法、 系统和设备
技术领域
本发明涉及下一代网络技术， 特别涉及一种在下一代网络中实现网 络地址转换穿越的方法、 系统和设备。 发明背景
下一代网络 （NGN, Next Generation Network )是基于时分复用 ( TDM, Time Division Multiplex ) 的公共电话交换网 （PSTN, Public Switched Telephone Network ) 与基于因特网协议 /异步传输模式（IP, Internet Protocol/ ATM , Asynchronous Transfer Mode )的分组网络相融合 的产物， 它使得在同一网络上实现语音、 视频以及数据等信息的综合业 务成为了可能， 标志着新一代电信网络时代的到来。
图 1为现有 NGN网络结构示意图。 如图 1所示， NGN网络主要包 括媒体网关（ MGW, Media Gateway )和媒体网关控制器（ MGC, Media Gateway Controller )。 其中， MGC, 用于实现呼叫状态的管理， 以及对 MGW承载资源的控制； MGW, 用于将媒体流类型由一种格式转换为另 一种格式， 例如， 将电路交换网中的 E1时隙转换为 IP网络中的实时传 输协议（ RTP, Real time Transport Protocol )媒体流， 并在 MGC的信令 控制下实现媒体流的建立、 修改、 释放以及资源管理。
如图 1所示，如果 MGW1和 MGW2所处的承载网络为同一个私有 网络或公有网络， 则 MGW1和 MGW2在信息交互过程中的 IP报文均 可直接发送到对方。但是，如果 MGW1和 MGW2处于不同的承载网络， 比如 MGW1 处于公有网络而 MGW2处于私有网络， 或者 MGW1 和 MGW2均处于私有网络， 但是两个网络不能实现 IP报文直接发送， 则 可能会出现媒体流单向导通或者彼此不通的情况。 同样的问题也可能存 在于媒体流一端为 MGW, 而另一端为会话初始协议 （ SIP, Session Initiation Protocol )终端、 H323终端、 电路域网络终端或者分组网络终 端等情况下。
现有技术中， 为实现 IP报文在私有网络和公有网络之间传送， 常采 用网络地址 /端口转换技术。 网络地址转换 （NAT , Network Address Translation )是一种用于将一个地址域， 如专用内联网 （Intranet ) 映射 为另一个地址域， 如互联网 （Internet )的标准技术。 NAT允许一个机构 专用 Intranet, 即私有网络中的终端透明地连接到公共域， 即公有网络中 的终端， 内部终端无需拥有注册的 Internet地址。
根据 NAT技术得到的 NAT穿越技术， 是指对私有网络上的终端采 用私有 IP地址， 通过出口的 NAT/防火墙（ FW, Fire Wall )接入公有网 络。 目前常用的两种 NAT 穿越方式为用户数据报协议 （UDP, User Datagram Protocol )对 NAT的筒单穿越（ STUN, Simple Traversal of UDP Through Network Address Translators ) 方式以及利用中继穿越 NAT ( TURN, Traversal Using Relay NAT )方式。
STUN方式的实现过程为： STUN客户端 （ CLIENT )通过 UDP向 NAT外的 STUN服务器（ SERVER )发送请求 STUN消息； STUN SERVER 接收到该请求消息后， 产生响应消息， 该响应消息中携带有发送请求消 息的源端口， 即 STUN CLIENT在 NAT上对应的外部接口信息； STUN SERVER通过 NAT将该响应消息发送给 STUN CLIENT; STUN CLIENT 通过该响应消息得知 NAT的外部地址，并将该外部地址填入到呼叫协议 的 UDP负载中， 以告知接收端本端的 RTP接收地址以及端口号为 NAT 外部的地址和端口号。 由于事先已经通过 STUN协议在 NAT上建立了 媒体流的 NAT映射表项， 所以媒体流在流经 NAT时可顺利穿越。 TURN方式的实现方法与 STUN类似，私有网络中的语音 IP( VoIP, Voice over IP )终端预先获知公有网络的服务地址，并将该服务地址填写 到 IP包载荷， 即信令的地址信息中。
现有技术中 NGN网络实现 NAT穿越的具体方式为：
私有网络中的 MGW1在能力协商时向 MGC上报的 RTP端点 RTP1 的本地会话描述协议（ SDP, Session Description Protocol)中的地址为私 有网络地址，假设为用户终端设备 ( CPE, Customer Premises Equipment ) 2。 MGC在发送给公有网络中的 MGW2中的 H.248消息中指定 MGW2 的 RTP端点 RTP2的远端地址为 CPE2, 这样， 按照 H.248协议规定， RTP2在随后向 MGW1发送媒体流时，会将媒体流发送到 CPE2的地址。 但是， CPE2是一个私有网络地址， 来自 RTP2的媒体流是无法到达的， 所以， 在端点 RTP1发出的媒体流通过 NAT时， NAT会将其地址 CPE2 转换为 CPE1 , 并在 H.248.37中新增一个携带有地址 CPE1信息的包信 号， 将该包信号下发给 RTP2, 以指示 RTP2作 NAT穿越。 RTP2用接收 到的地址 CPE1代替原有远端私网地址 CPE2,并将随后的媒体流发送到 CPE1。 NAT根据预先建立的地址映射关系，将 CPE1接收到的媒体流发 送到 MGW1的私网地址 CPE2。
该方法的问题在于， H.248.37中定义的 NAT穿越包需要私网中的端 点首先向公有网络中的端点发送媒体流， 才能激发 NAT产生地址映射， 而公网上的端点将接收到的媒体流源地址作为发送媒体流的目的地址。 但是很多情况下， 网络中只存在单向媒体流， 比如， 需要对端播放的回 铃音或者彩铃等， 因为此时被叫还没有摘机， 所以私网中的主叫不会有 媒体流发出。 另外， 当静音检测被激活时， 如果私网中的用户静音， 则 也没有从私网发往公网的媒体流， 相应地， 公网也无法把媒体流发送到 私网。 也就是说， 在 H.248.37定义的规范下， 私网中的端点必须先往公 网上的 IP端点上发送媒体流， 否则就无法实现媒体流的互通，从而影响 了 NGN网络中媒体流传输的稳定性。 发明内容
本发明实施例提供实现网络地址转换穿越的方法， 能够提高媒体流 传输的稳定性。
本发明实施例提供实现网络地址转换穿越的系统， 能够提高媒体流 传输的稳定性。
本发明实施例提供实现网络地址转换穿越的设备， 能够提高媒体流 传输的稳定性。
本发明实施例的技术方案是这样实现的：
一种实现网络地址转换穿越的方法， 该方法包括：
第一媒体网关 MGW获取本端以及对端的交互导通建立 ICE机制支 持设备的候选信息，并将本端的候选信息发送给所述 ICE机制支持设备； 所述第一 MGW根据所述候选信息与所述 ICE机制支持设备进行导 通检测； 体流的传送。
一种实现 NAT穿越的系统， 该系统包括： 第一 MGW以及 ICE机 制支持设备；
所述第一 MGW, 用于获取本端和对端 ICE机制支持设备的候选信 息， 根据所述候选信息与所述 ICE机制支持设备进行导通检测， 并根据 导通检测结果与所述 ICE机制支持设备进行媒体流的传送；
所述 ICE机制支持设备，用于获取本端和对端第一 MGW的候选信 息， 根据所述候选信息与所述第一 MGW进行导通检测， 并根据导通检 测结果与所述第一 MGW进行媒体流的传送。
一种实现网络地址转换 NAT穿越的设备， 该设备包括： 获取单元、 导通检测单元以及传送单元；
所述获取单元，用于获取本端和对端 ICE机制支持设备的候选信息， 并将本端的候选信息发送给所述 ICE机制支持设备；
所述导通检测单元， 用于根据所述候选信息， 与所述 ICE机制支持 设备进行导通检测；
所述传送单元， 用于根据导通检测结果， 与所述 ICE机制支持设备 之间进行媒体流的传送。
一种实现网络地址转换穿越的设备， 该设备包括： 控制单元以及第 一发送单元；
所述控制单元， 用于控制第一 MGW获取本端候选信息；
所述第一发送单元， 用于与 ICE机制支持设备进行信令交互， 以获 取 ICE机制支持设备的候选信息并发送给所述第一 MGW, 将所述第一 MGW的候选信息发送到所述 ICE机制支持设备。
可见， 采用本发明实施例的技术方案， MGW和网络中的 ICE机制 支持设备根据获取到的双方候选信息进行导通检测， 并且根据导通检测 的结果进行媒体流的 NAT穿越。相比于现有技术，本发明实施例所述方 案无需私有网络中的端点预先向 NAT发送媒体流来激发 NAT产生映射 地址，而且，解决了媒体流两端都在私有网络下的 NAT穿越问题；另夕卜， MGW不仅能够实现和其它支持本发明功能的 MGW之间的媒体流 NAT 流 NAT穿越， 从而提高了 NGN等包含 MGC和 MGW的网络中媒体流 传输的稳定性。 附图简要说明
下面将通过参照附图详细描述本发明的示例性实施例， 使本领域的 普通技术人员更清楚本发明的上述及其它特征和优点， 附图中：
图 1为现有技术中 NGN网络结构示意图；
图 2为本发明系统实施例的组成结构示意图；
图 3为本发明系统一个实施例的结构示意图；
图 4为本发明系统另一个实施例的结构示意图；
图 5为本发明设备实施例的组成结构示意图；
图 6为本发明方法实施例的流程图；
图 7为本发明方法另一个实施例的流程图。 实施本发明的方式
为使本发明的目的、 技术方案及优点更加清楚明白， 以下参照附图 并举实施例， 对本发明作进一步地详细说明。
正因为现有技术中 NGN网络在实现 NAT穿越时， 存在媒体流传输 稳定性无法保证的缺陷， 所以， 本发明实施例中希望提出一种不同于现 有技术的 NAT穿越方式， 以提高 NGN等包含 MGC和 MGW的网络中 媒体流传输的稳定性。
本发明实施例采用一种交互导通建立（ ICE, Interactive Connectivity Establishment )机制，该机制能够较好地解决基于 SIP的 NAT穿越问题， 其实现方法为： 将 STUN和 TURN等 NAT穿越方式进行整合， 在媒体 流的收发两端分别通过 STUN或 TURN方式产生一个候选（ candidate ) 列表， 并将两端的候选列表进行交叉配对， 生成一系列的候选对 (candidate pair) , 每一个候选对中均包括了一个本地候选和一个远端候 选； 然后对各候选对进行导通检测 （ Connectivity Check ) 和决策 ( Concluding ICE ), 将导通检测成功的候选对中优先级最高的候选对选 中 （selected ), 作为媒体流收发两端收发媒体流的通道。
ICE机制的具体实现过程为： 假设主叫端的 SIP终端为某个媒体流 分配了一个主机（host )地址， 假设该地址为 ho。 在发送呈现（offer ) 消息之前， ho通过 STUN方式获得一个映射公网地址， 该地址在 ICE 机制中被称为服务器反射 ( server reflexive )地址， 假设该地址为 sro。 此外， ho通过 TURN方式也获得一个公网地址， 该地址在 ICE机制中 被称为转播（relay )地址， 假设该地址为 ro。 这样， 在主叫端即获得了 三个候选信息： 主机候选 （host candidate ), 服务器反射候选 （server reflexive candidate )和转播候选 ( relayed candidate ), 这三个候选信息、^ J 地址分别是 ho , sro和 ro。 这里提到的地址的 IP版本可能是 IP V4,也可 能是 IP V6。主叫端获得三个候选信息后，通过 offer消息将其发送到被叫 端。 被叫端在接收到对端 （peer ) 的三个候选信息后， 用与对端同样的 方法获取自身的候选信息， 假设也获得了三个候选信息， 分别是被叫端 的 host candidate, server reflexive candidate和 relayed candidate, 对应的 地址分别为 ha, sra和 ra。 被叫端通过应答 ( answer ) 消息将这三个候 选信息发送到主叫端。 两端的候选信息交叉组合， 形成 9个候选对（实 际情况也可能没有这么多候选对， 例如主叫侧只有两个候选， 被叫侧只 有一个候选）， 每个候选对都可能形成一个有效的媒体流通道。 主叫端 和被叫端通过导通检测的机制， 按照优先级顺序， 对这 9个候选对进行 测试。 具体的测试方式是主叫端向被叫端发送 STUN 绑定（ binding )请 求消息，被叫端在接收到该 STUN binding请求消息后， 向主叫端回送应 答消息； 针对同一候选对， 被叫端向主叫端发送 STUN binding请求消 息， 主叫端同样回送应答消息。 这样， 就完成了对于一个候选对的导通 检测。 由于该过程包括了两个请求消息和两个应答消息， 所以可以筒称 为四步握手机制 (4-message handshake)。在选中优先级最高的导通检测成 功的候选对后，主叫端和被叫端即可根据该候选对所代表的 IP地址和端 口进行媒体流的收发。
本发明实施例中为解决现有技术中 NGN等包含 MGC和 MGW的 网络实现 NAT穿越时存在的问题，将 ICE机制引入到 MGC和 MGW的 功能中， 其实现方法是： 第一 MGW和 ICE机制支持设备 (即能够支持 ICE机制的设备 )获取本端和对端的候选信息； 第一 MGW和 ICE机制 支持设备根据候选信息进行导通检测； 第一 MGW和 ICE机制支持设备 根据导通检测结果进行媒体流的传送。
基于上述方法， 图 2为本发明系统实施例的组成结构示意图。 如图 2所示， 本发明系统的组成包括： 第一 MGW、 ICE机制支持设备以及第 一 MGC;
第一 MGW, 用于在第一 MGC的控制下获取本端候选信息， 并接 收第一 MGC发来的对端 ICE机制支持设备的候选信息， 与对端的 ICE 机制支持设备进行导通检测， 将导通检测结果上报给第一 MGC, 根据 导通检测结果进行媒体流的传送；
ICE机制支持设备，用于与第一 MGC进行信令交互，接收第一 MGC 发来的第一 MGW的候选信息， 并获取本端的候选信息， 将本端候选信 息发送给第一 MGC, 并与第一 MGW进行导通检测， 根据导通检测结 果进行媒体流的传送， 并在使用 （In-Use )候选对被更新时通知第一 MGC;
第一 MGC, 用于控制第一 MGW获取本端候选信息， 并与 ICE机 制支持设备进行信令交互， 以获取 ICE机制支持设备的候选信息并发送 给第一 MGW, 将第一 MGW的候选信息发送到 ICE机制支持设备， 接 收来自第一 MGW的导通检测结果， 在 In-Use候选对被更新时通知 ICE 机制支持设备，接收来自 ICE机制支持设备的 In-Use候选对被更新的消 其中， 第一 MGC进一步用于， 向第一 MGW发送保活报文类型和 / 或保活报文发送周期设置消息； 第一 MGW进一步用于， 接收来自第一 MGC的保活报文类型和 /或保活报文发送周期设置消息， 根据保活报文 或者， 第一 MGC进一步用于， 向第一 MGW发送保活报文发送指 示； 第一 MGW进一步用于，接收来自第一 MGC的保活报文发送指示， 并在接收到该保活报文发送指示后，向 ICE机制支持设备发送保活报文。
ICE机制支持设备可以为被第一 MGC控制的第二 MGW, 也可以 是第二 MGW和第二 MGC的组合， 还可以是支持 ICE机制的 SIP代理 ( agent ) , 或者支持 ICE机制的 IMS网络等。
图 3为本发明系统一个实施例的结构示意图， 本实施例中， ICE机 制支持设备为第二 MGC203 和第二 MGW204 的组合， 其中， 第二 MGW204, 用于接收来自第二 MGC203的对端第一 MGW202的候选信 息， 以及来自第二 MGC203的候选搜集 (Gathering Candidates)指示， 根 据候选搜集指示通过 STUN 等方式示获取本端候选信息并发送给第二 MGC203; 根据本端和对端的候选信息与第一 MGW202进行导通检测； 并根据导通检测结果与第一 MGW202之间进行媒体流的传送；
第二 MGC203 , 用于接收来自第一 MGC201的第一 MGW202的候 选信息， 向第二 MGW204发送候选搜集指示， 将第二 MGW204的候选 信息发送给第一 MGC201 , 接收来自第二 MGW204的导通检测结果。
这里要注意的是， 在实际应用中， 也可以不使用候选搜集指示， 而 是规定 MGW在媒体能力协商过程中分配 RTP端点时自动搜集候选信息 上报。 如果导通检测的结果与之前的 In-Use候选不同， MGC可以通过 修改（modify ) 消息更新本端 MGW上 RTP端点的 SDP, 还可以通过 SIP的更新呈现（Updated Offer ) 消息通知对端。 MGC接收到对端发送 来的 Updated Offer消息后，可以通过 modify消息更新本端 MGW上 RTP 端点的 SDP。
本实施例中， 为便于描述， 将第一 MGC201和第一 MGW202分别 用 MGC1 202和 MGW1 201表示； 第二 MGC203和第二 MGW204分别 用 MGC2 203和 MGW2 204表示， 如图 3所示， 假设 MGW1 202处于 私有网络， MGW2 204处于公有网络， 则该系统的工作流程为：
MGW1 202侧发起呼叫， MGC1 201在 MGW1 202上建立 RTP端点 RTP1 ,在进行媒体能力协商的过程中， MGW1 202在 MGC1 201的控制 下获取候选信息， 包括主机候选信息、 服务器反射候选信息以及转播候 选信息，并将获取的候选信息通过 H.248协议发送给 MGC1 201。 MGC1 201 通过 SIP协议将该候选信息发送给控制处于公有网络中的 MGW2 204的 MGC2 203, MGC2 203将该候选信息进一步发送给 MGW2 204。 MGW2 204在接收到 MGW1 202的候选信息后， 通过与 MGW1 202同 样的方式， 获取自身的候选信息， 本实施例中， 因为处于公有网络中， 所以 MGW2 204的候选信息只需要一个主机候选信息。 MGW2 204将该 主机候选信息通过 MGC2 203和 MGC1 201发送给 MGW1 202。 这样， 两端的 MGW都知道了本端和对端的候选列表。 然后， MGW1 202和 MGW2 204在各自 MGC 的指示下或自动发起导通检测过程。 比如， MGW1 202在接收到 MGW2 204的候选信息后， 即可自动发起导通检 测， 具体导通检测过程与现有技术相同， 即按照 ICE机制的标准的规定 执行。 此处， MGC1 201和 MGC2 203需要指示出对应的 MGW是否为 控制角色， 由控制角色选择最终的候选对。 MGC1 201和 MGC2 203还 需要指示出对应的 MGW是否为会话发起方， 该信息在计算候选对优先 级别的时候有用。 该指示可以是一个 H.248属性， 或者是 H.248信号， 或者是事件的一个参数， 也可以通过规则设定， 例如： 增加 RTP端点时 如果没有远端 （remote ) SDP, 则为呼叫的发起方， 否则就是应答方 ( answerer )。 导通检测完成， 根据 MGC1 201和 MGC2 203进行的事件 设置， MGW1 202和 MGW2 204将导通检测结果上报给 MGC1 201和 / 或 MGC2 203。 后续过程中， MGW1 202和 MGW2 204即可根据导通检 测结果进行媒体流的传送。 参照 ICE机制的规定， 如果 In-Use的候选和 导通检测结果中被选中的候选不同， 则还需要更新 SDP内容。
这里需要注意的是， ICE机制中有轻量执行（ Lite Implementation ) 的概念， 轻量执行的一端不需要搜集候选， 这种情况可以理解为只有一 个 host候选。
图 3中所示的 NAT和 STUN服务器在本实施例中的连接方式以及 实现的功能与现有技术中相同， 不再赘述。 在实际应用中， MGW2 204 和 MGW1 202可以由同一个 MGC控制， 此时 MGW2 204的功能与 MGW1 202相同， 即， 用于接收来自第一 MGC201 的关于对端第一 MGW202的候选信息， 并获取本端候选信息， 将本端候选信息发送给第 一 MGC201 , 并根据本端和对端候选信息与第一 MGW202进行导通检 测。
图 4为本发明系统另一个实施例的结构示意图。 如图 4所示， 本实 施例与实施例一相比，区别仅在于，实施例一中的 MGW2 204和 MGC2 203在本实施例中被 SIP终端 303替代， 本实施例系统的工作方式与实 施例一相比并无本质区别， 不再赘述。
基于上述介绍， 图 5为本发明设备实施例的组成结构示意图。 如图 5所示， 该设备包括： 获取单元 501、 导通检测单元 502以及传送单元 503; 获取单元 501 ,用于获取本端和对端 ICE机制支持设备的候选信息， 并将本端的候选信息发送给 ICE机制支持设备；
导通检测单元 502, 用于根据所述候选信息， 与 ICE机制支持设备 进行导通检测；
传送单元 503, 用于根据导通检测结果， 与 ICE机制支持设备之间 进行媒体流的传送。
该设备中进一步包括： 接收单元 504, 用于接收来自 MGC的候选 搜集指示或导通检测发起指示； 获取单元根据候选搜集指示， 获取本端 的候选信息； 导通检测单元根据导通检测发起指示， 发起与所述 ICE机 制支持设备之间的导通检测。
此外， 该设备中还可进一步包括： 上报单元 505, 用于将导通检测 结果上报给 MGC; 保活报文发送单元 506, 用于接收来自 MGC的保活 报文类型和 /或保活报文发送周期设置消息， 按照保活报文类型和 /或保 活报文发送周期向 ICE机制支持设备发送保活报文； 或者， 接收来自 MGC的保活报文发送指示， 按照指示向 ICE机制支持设备发送保活报 文。
上述 MGC可具体包括： 控制单元以及第一发送单元；
控制单元，用于控制第一 MGW获取本端候选信息；第一发送单元， 用于与 ICE机制支持设备进行信令交互， 以获取 ICE机制支持设备的候 选信息并发送给第一 MGW, 将第一 MGW的候选信息发送到 ICE机制 支持设备。
此外， 该 MGC中还可进一步包括：
第二发送单元， 用于向第一 MGW发送候选搜集指示， 以指示第一 MGW获取本端的候选信息；
第三发送单元， 用于向第一 MGW发送导通检测发起指示； 第四发送单元， 用于向第一 MGW发送第一 MGW是否为控制角色 的指示信息， 或者， 向第一 MGW发送第一 MGW是否为会话发起方的 指示信息；
第五发送单元，用于向第一 MGW发送保活报文类型和 /或保活报文 发送周期设置消息，以指示第一 MGW按照所述保活报文类型和 /或保活 报文发送周期向 ICE机制支持设备发送保活报文； 或者， 用于向第一 MGW发送保活报文发送指示， 以指示第一 MGW按照所述指示向 ICE 机制支持设备发送保活报文。
图 6为本发明方法实施例的流程图， 如图 6所示， 包括以下步骤： 步骤 601: 第一 MGW和 ICE机制支持设备都获得本端和对端的候 选信息。
本步骤中，第一 MGW和 ICE机制支持设备均需要获取本端以及对 端的候选信息， 具体获取方式为：
第一 MGW获取本端候选信息， 并通过第一 MGC将本端的候选信 息发送给对端的 ICE机制支持设备；对端的 ICE机制支持设备获取本端 的候选信息， 并通过第一 MGC将本端的候选信息发送给第一 MGW; 或者， 对端的 ICE机制支持设备获取本端的候选信息， 并通过第一 MGC将本端的候选信息发送给第一 MGW;第一 MGW获取本端的候选 信息， 并通过第一 MGC将本端的候选信息发送给对端的 ICE机制支持 设备。
该步骤包含在会话两端媒体能力协商过程中， 上述两种方式分别对 应第一 MGW作为会话的发起方（ offer ) 以及第一 MGW作为会话的应 答方 （answerer ) 两种情况。 但是， 由于媒体能力协商过程的随意性和 复杂性， 有时候该过程的执行并不那么严格， 例如， 第一 MGW获取本 端候选信息并且上报给第一 MGC后，第一 MGC可能并不将第一 MGW 的候选信息通知到对端的 ICE机制支持设备， 即 offer消息中不带 SDP, 而是等对端 ICE机制支持设备在 answer消息中通过 SDP带回对端的候 选信息后， 第一 MGC再将本端的候选信息发送到对端。 所以， 该步骤 的实质是： 在会话的媒体能力协商阶段， 两端各自搜集本端候选信息并 且将该候选信息通过信令， 如 H.248或者 SIP等与对端进行交换， 其具 体实现过程可能很灵活。
第一 MGW获取本端候选信息之前， 可以进一步包括第一 MGC向 第一 MGW发送候选搜集指示的步骤； 相应地， 第一 MGW在接收到该 候选搜集指示后，获取本端的候选信息。其中， 第一 MGC向第一 MGW 发送候选搜集指示的方式为： 第一 MGC通过扩展的 SDP向第一 MGW 发送候选搜集指示。
第一 MGC和 ICE机制支持设备获取各自候选信息的方式与现有技 术 ICE机制中 SIP终端获取候选信息的方式相同。
上述 ICE机制支持设备可以为第二 MGW , 也可以是第二 MGW和 第二 MGC的组合， 还可以是一个支持 ICE机制的 SIP agent等。 若 ICE 机制支持设备为第二 MGC和第二 MGW的组合， 则 ICE机制支持设备 获取本端候选信息的方式为： 第二 MGC接收来自第一 MGC的关于第 一 MGW的候选信息， 并将该候选信息发送给第二 MGW; 第二 MGW 创建 RTP端点， 并在第二 MGC的指示下获取本端的候选信息。 若 ICE 机制支持设备为 SIP终端， 则 ICE机制支持设备获取本端候选信息的方 式为： SIP终端在接收到第一 MGW的候选信息后， 自动获取本端的候 选信息。
以上仅为举例说明， 在实际应用中， 呼叫流程也可能不是由第一 MGW, 而是由对端的 ICE机制支持设备发起； 而且， 第一 MGW和 ICE 机制支持设备获取本端候选信息以及获取对端候选信息的次序也可能 有多种排列， 这和具体的流程相关。
步骤 602: 第一 MGW和 ICE机制支持设备根据候选信息进行导通 检测。
在获取了本端以及对端的候选信息后，第一 MGW和 ICE机制支持 设备即可进行导通检测， 以确定最终用于传输媒体流的候选对。
本步骤中， 第一 MGW和 /或 ICE机制支持设备可以是自动发起导 通检测， 也可以是在第一 MGC的控制下发起导通检测， 具体的承载层 前， 第一 MGC需要通过扩展 H.248协议向第一 MGW发送导通检测发 起指示， 和 /或指示第一 MGW是否为控制角色的指示信息， 和 /或者本 端是否为会话发起方的指示信息。 控制角色指示信息用于指示第一 MGW是否为控制角色， 由控制角色来完成最终的候选对选择； 会话发 起方指示信息用于指示由本端计算候选对的优先级别， 该指示也可以用 前面描述过的， 第一 MGW通过媒体协商过程中的 H.248消息中是否携 带有远端 (remote) SDP等方法来区分自身是否为会话的发起方。 如果是 自动发起的导通检测， 则两端在获得候选信息后即可发起导通检测过 程。
导通检测完成后， 第一 MGW根据第一 MGC上的事件设置将导通 检测结果通过事件上报或在 H.248请求消息的应答中上报等方式上报给 第一 MGC; 上报时机可以是在导通检测完成后， 也可以是在导通检测 失败后。
步骤 603： 第一 MGW和 ICE机制支持设备根据导通检测结果进行 媒体流的传送。
本步骤中，第一 MGW和 ICE机制支持设备根据步骤 602中得到的 导通检测结果进行媒体流的传送。 在实际应用中， 例如呼叫保持（hold ) 等情况下， 第一 MGW和 ICE机制支持设备可能不会连续收发媒体流， 也就是说， 可能在某一段时间内， 网络中没有媒体流的传送， 这种情况 下， 为维持通道的有效性， 第一 MGW需要向对端 ICE机制支持设备发 送保活 （keepalive )报文， 并且可能需要应答对端 ICE机制支持设备发 送来的保活报文。 该保活报文可能是需要应答的 STUN绑定（binding ) 请求消息， 也可能是不需要应答的无操作 ( No-Op ) 包或者静音包等。 保活报文的发送周期要小于 NAT上地址映射保持的时间，保活报文沿着 媒体流的路径传送。 第一 MGC 可以通过扩展 H.248 协议预先向第一 MGW发送保活报文类型和 /或保活报文发送周期设置消息； 相应地， 第 一 MGW在需要发送保活报文时， 就会按照设置好的保活报文类型和 / 或保活报文发送周期向 ICE机制支持设备发送保活报文； 或者， 第一 MGC通过扩展 H.248协议向第一 MGW发送保活报文发送指示； 第一 MGW在接收到第一 MGC的保活报文发送指示后， 向 ICE机制支持设 备发送保活报文。 该保活报文发送指示中也可以携带有保活报文类型和 /或保活报文发送周期信息。
步骤 601 - 603 中所提到的候选信息为主机候选信息、 服务器反射 候选信息以及转播候选信息中的一个或多个。
另夕卜， 还有一个对端反射 ( peer reflexive )候选的概念。 在进行导 通检测的过程中， 因为导通检测使用了 STUN绑定请求消息， 该消息的 应答中携带了反射 ( reflexive )地址（本发明实施例中的地址通常是指 IP地址和端口）， 如果该地址和已有的本地候选地址不同， 则将该反射 地址称为对端反射地址， 该地址和服务器反射地址的区别在于， 前者是 对端反射生成的， 而后者是在 STUN服务器上反射生成的。 对于对端来 说，如果导通检测中收到的 STUN绑定请求消息的源地址和已有的所有 远端候选不同， 而且该导通检测成功， 则可以确定这是一个对端反射远 端候选 ( peer reflexive remote candidate )。 对端反射候选如果成为选中的 候选， 用于媒体流的传送， 则该地址需要上报给 MGC, 用于门控等用 途。
图 7为本发明方法另一个实施例的流程图， 本实施例所依据的系统 结构如图 3所示， 即 ICE机制支持设备为第二 MGC和第二 MGW的组 合。本实施例中，为便于描述，将第一 MGC和第一 MGW分别用 MGC1 和 MGW1表示；第二 MGC和第二 MGW分别用 MGC2和 MGW2表示， 该方法实施例包括以下步骤：
步骤 701： MGW1和 MGC2获取本端以及对端的候选信息。
MGC1侧发起呼叫， 在媒体能力协商过程中建立 RTP端点 RTP1 , 该 RTP端点有一个本地网络接口地址 ho, ho可能是一个 IPV4地址加端 口， 也可能是一个 IPV6地址加端口， 本实施例中假设为 IPV4地址加端 口。 MGW1通过 STUN服务器获得服务器反射候选信息 sro以及转播候 选信息 ro。 上述候选信息是在媒体流协商过程中， MGC1通过扩展 SDP 要求 MGW1去获取的， 相应地， MGW1通过扩展 SDP将候选信息上报 给 MGC1。 比如， 当前 MGC1 需要 MGW1 上报服务器反射候选， 则 MGC1发送给 MGW1的 SDP用如下一个 "a=" 行形式表示：
a=candidate: 2 1 UDP 1694498562 $ $ typ srflx raddr $ rport $;
前两个 "$" 分别表示需要 MGW1上报的服务器反射地址和端口； 后两个 "$" 分别表示需要 MGW1上报的主机地址和端口；
"a=candidate" 表示本行为的代理属性；
"UDP" 表示使用 UDP协议；
"typ srflx" 表示该候选为服务器反射候选；
"raddr" 表示需要 MGW1填入的 (related)地址；
"rport" 表示需要 MGW1填入的端口。 相应地， MGW1应答时在 SDP的相应位置上填入获取的服务器反 射候选地址和端口， 如下所示：
a=candidate: 2 1 UDP 1694498562 192.0.2.3 45664 typ srflx raddr 10.0.1.1 rport 8998。
也可以是如下形式：
a=candidate:?？? ?？? srflx
来要求 MGW搜集上报服务器反射候选信息。
也可以是如下形式：
a=candidate:? ? ? ? ? ? *
来要求 MGW搜集上报各种候选信息。
总之， 具体的扩展方式不唯一。
MGC1获得 MGW1的三个候选信息， 并可以指定将其中的一个设 置到 SDP的 m/c行作为使用候选（ In-Use candidate ); 后续步骤 702中， 如果导通检测得到的候选信息与 In-Use candidate 中存储的候选信息不 符，则 MGC1可以用导通检测得到的候选信息对 m/c行 In-Use candidate 中的候选信息进行替换。 MGC1将得到的三个候选信息通过 SIP信令送 到 MGC2, 并由 MGC2发送给 MGW2。 与 MGW1类似， MGW2上创 建了 RTP端点 RTP2 , 并获取候选信息， 因为 MGW2处于公有网络中， 所以只需一个候选信息， 即主机候选信息 ha, 该主机候选信息通过 MGC2和 MGC1发送到 MGW1。 这样， MGW1和 MGW2都知道了本 端和对端的候选信息， 即候选列表， 并形成了三个候选对， 即（ho、 ha )、 ( sro、 ha ) 以及 ( ro、 ha )。
步骤 702: MGW1发起导通检测，并将导通检测结果上报给 MGC1。 本实施例中， MGC1通过扩展的 H.248协议指示 MGW1发起导通 检测、指示 MGW1是否为控制角色以及指示 MGW1是否为会话发起方。 这里所提到的扩展 H.248协议的方式可以是指在原有 H.248协议的基石出 上新定义一个 ostuncc包， 该 ostuncc包中包括：
信号 sec:用于指示 MGW1发起 ICE机制的导通检测， 该信号具体 标示要进行导通检测的媒体流， 还可进一步携带指示参数， 如 H.248的 流标识 （stream ID )、 ICE机制的基础 （foundation ) 编号和组成标识 ( component-id )等信息中的一个或多个； 或者， 也可以不携带这些参 数， 而是对该信号作用范围内的所有媒体流进行导通检测。
属性 control: 用于指示 MGW1为控制角色 （controlling role )还是 被控制角色 （controlled role ), 该属性可以放在本地控制描述符 ( Local Control Descriptor ) 下， 本实施例中假设 MGW1 为控制角色， 即， 由 MGW1决定最终选择的候选对。
属性 side: 用于指示 MGW1端为 offer端还是 answer端， 该值用于 候选对的优先级计算。
这两个属性携带的信息也可以通过 sec信号的参数来传递。
MGW1 和 MGW2之间进行导通检测， 并将导通检测结果上报给 MGC,控制角色和被控制角色， 即 MGW1和 MGW2均可上 4艮导通检测 结果， ICE 机制规定导通检测的状态分为进行 （Running ) 和完成 ( Completed )两种。 上报时机可以是在导通检测完成， 也可以是在导通 检测失败后； 上报的方式可以采用事件上报方式， 也可以采用在 H.248 请求消息的应答中上报的方式； 上报内容可以包括以下内容中的一项或 多项：
1、各个候选对的当前状况，如：等待（ Waiting )、处理中（ In-Progress )、 成功 /有效（Succeeded ), 失败（Failed )或冻结 （Frozen );
2、 被选中的候选对， 该候选对将被用于媒体流的传送；
3、 如果被选中的候选对中包括了对端反射候选 （Peer Reflexive Candidate )，则还需要上报对端反射的类型， 即是本地（local )的对端反 射还是对端（remote )的对端反射， 并且上 该对端反射候选的 IP地址 和端口， 该 IP地址和端口将被用于后续处理， 例如门控等。
本实施例中， 假设由 MGW1负责上报导通检测结果， 则 MGW1同 样需要扩展 H.248协议来传送该导通检测结果信息， 这可以通过在新定 义的 ostuncc包中定义一个事件 ccr来实现。该事件可以设置用来上报某 个 RTP端点上所有的媒体流的导通检测结果， 或者该 RTP端点上指定 的 streamID上所有媒体流的导通检测结果。事件上报时携带的信息包括 H.248的 stream ID、 Group ID、 本端 foundation编号、 对端 foundation 编号、 component-id、 对端反射类型 (local还是 remote)、 对端的反射 IP 地址和端口以及反射 IP地址和端口，以及是否为选中候选对等信息中的 一个或多个。
上报事件参数 result的数据类型为如下格式的字符串列表：
Streamed"： "groupID"： "foundation-L"： "foundation-R"： "component-id"： " state [： peer Reflexive type and address] [： selected]；
其中， streamID为 H.248的流 ID;
groupID为 H.248的组 ID;
foundation-L为候选对中的本端 foundation编号；
foundation-R为候选对中的对端 foundation编号；
component-id 为候选对的 component-id , 本端和对端使用相同的 component-id;
state为矣选于的当前^ 态,取值^口： Waiting, In- Progress, Succeeded、 Failed或 Frozen;
peer Reflexive type and address为对端反射候选的类型， 两种类型包 括本地对端反射候选和远端对端反射候选。 一个候选对中可能只有一端 产生对端反射候选， 也可能是两端都产生了对端反射候选。 该候选对中 的所有对端反射候选的类型以及各自对应的对端反射 IP地址和端口都 可以通过 peer Reflexive type and address上报。
Selected用于标识本候选对是否被选中用来传送媒体流。
ICE机制的标准中规定，在一个候选对中，两个候选的 component-id 必须相同，如果 MGC对 component-id进行特殊处理，保证在不同的 group 和 stream 中， component-id 不会重复， 例如： 对 MGW 进行内部的 component-id重分配， 或者采取了其它方式达到相同目的， 则 MGW不 需要上报 streamID 和 groupID,但是可能需要上报两个不同的 component-id
如果导通检测失败， 则可以通过返回错误码或者返回空串来表示。 最终的实施方案中， 事件上报的内容可以包括上述事件上报内容中 的部分或者全部。
另外， 如果上报的导通检测结果被排序， 例如按照候选对的优先级 别排序后上报， 则 elected参数也可以不需要。
另外， 为了避免上报的消息过长， 可以考虑只上报某些状态的候选 对， 例如导通检测成功以及失败的候选对， 对没有检测的候选对没有必 要上报， 可以通过在事件设置中增加参数等方式达到该目的。
步骤 703: MGW1和 MGW2根据导通检测结果进行媒体流传送。
MGC1和 MGC2根据上报的导通检测结果对 MGW1和 MGW2的 SDP进行更新， 保证 m/c行中的 IP地址和端口为被选中 （ selected ) 的 候选的 IP地址和端口。需要说明的是，该操作可能是多余的，因为 MGW1 和 MGW2在导通检测的过程中已经获得了选中的候选对， 这里作出说 明主要是为了和当前的 ICE机制标准对齐。
本步骤中， 若选中的候选对中较长时间没有媒体流的传送， 则 MGWl将向 MGW2发送保活报文， 以便维持该候选对的有效。 这需要 MGC1通过扩展的 H.248预先为 MGW1设置好保活报文的类型和 /或保 活报文的发送周期； 之后， MGW1在需要发送保活报文的时候， 就会按 照设置好的类型和 /或周期进行保活报文发送； 或者， MGC1 向 MGW1 发送保活报文发送指示， MGW1在每次接收到该保活报文发送指示后， 即向 MGW2发送保活报文。 保活报文发送周期的计算时间从媒体流停 止收发开始， 如果一直有媒体流， 则不需要发送保活报文。 为此， 在 ostuncc包中需要加入以下内容：
属性 kaType: 用于指示保活报文的类型， 如空操作 ( No-Op )报文， 静音报文和 STUN 绑定请求报文等；前两种类型的报文是考虑在不支持 STUN/ICE的设备之前的 NAT保活， 这样就不限于要候选对信息， 报活 报文在媒体流的传送路径上发送 ， 该属性可 以 放在 LocalControlDescriptor下；
属性 Tr: 用于指示保活保文的发送周期， 该属性可以考虑对不同的 媒体流单独设置 Tr值，也可以对所有媒体流进行设置，该属性可以放在 LocalControlDescriptor下；
保活报文的发送也可以通过信号的方式来实现， 该信号可以具体指 定需要发送保活报文的媒体流路径， 也可以指示在所有的媒体流路径上 发送保活报文； 该信号中还可以通过参数设置保活报文类型和 Tr属性。
除了上述介绍的内容以外， ostuncc 包中还可进一步包括属性 iuType: 用于指示步骤 701中提到的 In-Use candidate的类型。 本实施例 中 , In-Use candidate的类型包括 host candidate, server reflexive candidateh 和 relayed candidate三种，这三种类型可分别被定义成 he ( 0x0001 ), src ( 0x0002 )和 rc ( 0x0003 ), 该属性同样可以放在 LocalControlDescriptor 下。 MGW根据该属性值将相应的候选类型的 IP地址和端口放到 SDP 的 m/c行中。
本实施例介绍的是当媒体流收发两端均为 MGW时本发明所述方案 的实现流程， 当 MGW和其它 ICE机制支持设备进行媒体流交互时， 具 体实现流程与图 7所示类似， 本领域技术人员可以较为容易的推出， 此 处不再赘述。
可见， 采用本发明实施例的技术方案， MGW和网络中的 ICE机制 支持设备根据获取到的双方候选信息进行导通检测， 并且根据导通检测 的结果进行媒体流的 NAT穿越。相比于现有技术，本发明实施例所述方 案无需私有网络中的端点预先向 NAT发送媒体流来激发 NAT产生映射 地址，而且，解决了媒体流两端都在私有网络下的 NAT穿越问题；另夕卜， MGW不仅能够实现和其它支持本发明功能的 MGW之间的媒体流 NAT 流 NAT穿越， 从而提高了 NGN等包含 MGC和 MGW的网络中媒体流 传输的稳定性。
综上所述， 以上仅为本发明的较佳实施例而已， 并非用于限定本发 明的保护范围。 凡在本发明的精神和原则之内， 所作的任何修改、 等同 替换、 改进等， 均应包含在本发明的保护范围之内。

Claims

权利要求书
1、 一种实现网络地址转换穿越的方法， 其特征在于， 该方法包括： 第一媒体网关 MGW获取本端以及对端的交互导通建立 ICE机制支 持设备的候选信息，并将本端的候选信息发送给所述 ICE机制支持设备； 所述第一 MGW根据所述候选信息与所述 ICE机制支持设备进行导 通检测； 体流的传送。
2、 根据权利要求 1所述的方法， 其特征在于， 第一 MGW获取本 端以及对端的 ICE机制支持设备的候选信息， 并将本端的候选信息发送 给所述 ICE机制支持设备的方式为：
所述第一 MGW 获取本端的候选信息， 通过第一媒体网关控制器 MGC与所述 ICE机制支持设备进行交互， 将本端的候选信息发送给所
3、 根据权利要求 1所述的方法， 其特征在于， 所述第一 MGW获 取本端候选信息之前， 进一步包括：
所述第一 MGW接收第一 MGC通过会话描述协议 SDP发来的候选 搜集指示， 根据所述候选搜集指示获取本端的候选信息。
4、 根据权利要求 1 所述的方法， 其特征在于， 所述进行导通检测 之前， 进一步包括：
所述第一 MGW接收第一 MGC发来的导通检测发起指示。
5、 根据权利要求 1 所述的方法， 其特征在于， 所述进行导通检测 之前， 进一步包括：
所述第一 MGW接收第一 MGC通过扩展 H.248协议发来的第一 MGW是否为控制角色的指示信息， 按照该指示信息在随后的导通检测 过程中担任控制或者被控制角色。
6、 根据权利要求 1 所述的方法， 其特征在于， 所述进行导通检测 之前， 进一步包括：
所述第一 MGW接收第一 MGC通过扩展 H.248协议发来的第一 MGW是否为会话发起方的指示信息， 按照该指示信息在随后的导通检 测过程中计算根据本端和对端的候选信息所生成的候选对的优先级。
7、 根据权要求 1所述的方法， 其特征在于， 所述进行导通检测后， 进一步包括： 由所述第一 MGW将导通检测结果上报给第一 MGC, 所 述上报的方式为：
所述第一 MGW通过扩展的 H.248协议采用事件上报方式， 或在 一 MGC。
8、 根据权利要求 7所述的方法， 其特征在于， 所述导通检测结果 中携带有各候选对的检测结果信息， 包括： 流标识 stream ID、 组标识 Group ID、 本端的基础 foundation编号、 对端的 foundation编号、 组成 标识 component-id、 对端反射 peer reflexive类型、 对端反射 IP地址和端 口， 以及本候选对是否为选中候选对中的一种或任意组合。
9、 根据权利要求 1 所述的方法， 其特征在于， 所述进行媒体流传 送过程中进一步包括：
所述第一 MGW接收第一 MGC通过扩展 H.248协议发来的保活报 文类型和 /或保活报文发送周期设置消息，根据所述接收到的保活报文类 或者， 所述第一 MGW接收第一 MGC通过扩展 H.248协议发来的 保活报文发送指示， 根据所述保活报文发送指示向所述 ICE机制支持设 备发送保活报文； 文。
10、 根据权利要求 1所述的方法， 其特征在于， 所述候选信息为主 机候选信息、 服务器反射候选信息、 转播候选信息以及对端反射候选信 息中的一个或任意组合。
11、 根据权利要求 1所述的方法， 其特征在于， 所述 ICE机制支持 设备为：被第一 MGC控制的第二 MGW、第二 MGC和第二 MGW的组 合， 或 SIP代理。
12、一种实现网络地址转换穿越的系统， 其特征在于， 该系统包括： 第一 MGW以及 ICE机制支持设备；
所述第一 MGW, 用于获取本端和对端 ICE机制支持设备的候选信 息， 根据所述候选信息与所述 ICE机制支持设备进行导通检测， 并根据 导通检测结果与所述 ICE机制支持设备进行媒体流的传送；
所述 ICE机制支持设备，用于获取本端和对端第一 MGW的候选信 息， 根据所述候选信息与所述第一 MGW进行导通检测， 并根据导通检 测结果与所述第一 MGW进行媒体流的传送。
13、 根据权利要求 12所述的系统， 其特征在于， 该系统中进一步 包括： 第一 MGC, 用于控制所述第一 MGW获取本端候选信息， 并与 所述 ICE机制支持设备进行信令交互，以获取 ICE机制支持设备的候选 信息并发送给所述第一 MGW, 将所述第一 MGW的候选信息发送到所 述 ICE机制支持设备。
14、 根据权利要求 12或 13所述的系统， 其特征在于， 所述 ICE机 制支持设备为：被第一 MGC控制的第二 MGW、第二 MGC和第二 MGW 的组合或 SIP代理。
15、 根据权利要求 13所述的系统， 其特征在于，
所述第一 MGC进一步用于向所述第一 MGW发送保活报文类型和 / 或保活报文发送周期设置消息；
所述第一 MGW进一步用于接收来自所述第一 MGC的保活报文类 型和 /或保活报文发送周期设置消息， 根据所述保活报文类型和 /或保活
16、 根据权利要求 13所述的系统， 其特征在于，
所述第一 MGC进一步用于向所述第一 MGW发送保活报文发送指 示；
所述第一 MGW进一步用于接收来自所述第一 MGC的保活报文发 送指示， 并在接收到所述保活报文发送指示后， 向所述 ICE机制支持设 备发送保活报文。
17、一种实现网络地址转换穿越的设备， 其特征在于， 该设备包括： 获取单元、 导通检测单元以及传送单元；
所述获取单元，用于获取本端和对端 ICE机制支持设备的候选信息， 并将本端的候选信息发送给所述 ICE机制支持设备；
所述导通检测单元， 用于根据所述候选信息， 与所述 ICE机制支持 设备进行导通检测；
所述传送单元， 用于根据导通检测结果， 与所述 ICE机制支持设备 进行媒体流的传送。
18、 根据权利要求 17 所述的设备， 其特征在于， 该设备中进一步 包括： 接收单元， 用于接收来自 MGC的候选搜集指示或导通检测发起 指示；
所述获取单元根据所述候选搜集指示， 获取本端的候选信息； 所述导通检测单元根据所述导通检测发起指示，发起与所述 ICE机 制支持设备之间的导通检测。
19、 根据权利要求 17 所述的设备， 其特征在于， 该设备中进一步 包括： 上报单元， 用于将导通检测结果上报给 MGC。
20、 根据权利要求 17 所述的设备， 其特征在于， 该设备中进一步 包括： 保活报文发送单元， 用于接收来自 MGC的保活报文类型和 /或保 活报文发送周期设置消息，按照所述保活报文类型和 /或保活报文发送周 期向所述 ICE机制支持设备发送保活报文；
或者， 接收来自所述 MGC的保活报文发送指示， 按照所述指示向 所述 ICE机制支持设备发送保活报文。
21、一种实现网络地址转换穿越的设备， 其特征在于， 该设备包括： 控制单元以及第一发送单元；
所述控制单元， 用于控制第一 MGW获取本端候选信息；
所述第一发送单元， 用于与 ICE机制支持设备进行信令交互， 以获 取 ICE机制支持设备的候选信息并发送给所述第一 MGW, 将所述第一
MGW的候选信息发送到所述 ICE机制支持设备。
22、 根据权利要求 21 所述的设备， 其特征在于， 该设备中进一步 包括： 第二发送单元， 用于向所述第一 MGW发送候选搜集指示， 以指 示所述第一 MGW获取本端的候选信息。
23、 根据权利要求 21 所述的设备， 其特征在于， 该设备中进一步 包括： 第三发送单元， 用于向所述第一 MGW发送导通检测发起指示。
24、 根据权利要求 21 所述的设备， 其特征在于， 该设备中进一步 包括： 第四发送单元， 用于向所述第一 MGW发送第一 MGW是否为控 制角色的指示信息， 或者， 向所述第一 MGW发送第一 MGW是否为会 话发起方的指示信息。
25、 根据权利要求 21 所述的设备， 其特征在于， 该设备中进一步 包括： 第五发送单元， 用于向所述第一 MGW发送保活报文类型和 /或保 活报文发送周期设置消息， 以指示所述第一 MGW按照所述保活报文类 型和 /或保活报文发送周期向所述 ICE机制支持设备发送保活报文； 或 者， 用于向所述第一 MGW发送保活报文发送指示， 以指示所述第一 MGW按照所述指示向所述 ICE机制支持设备发送保活报文。
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