CN101043475A

CN101043475A - Process and system for media flow transverse network address conversion

Info

Publication number: CN101043475A
Application number: CNA2006100944969A
Authority: CN
Inventors: 丁晓强; 简海燕; 孟庆锋; 苏炜; 刘慈; 文楷; 黄福清; 薛莉莉
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2006-06-30
Filing date: 2006-06-30
Publication date: 2007-09-26
Anticipated expiration: 2026-06-30
Also published as: WO2008003214A1; CN100596125C

Abstract

The disclosed address conversion method for media flow crossing network comprises: it transmits user media flow to the BGF entity; the latter matches the media mapping relation binding with media mapping message according to mark and original address in media to determine the port, and transmits the media flow. It also discloses a network system for the address conversion.

Description

A kind of method and system of crossing medium-flow over network address conversion

Technical field

The present invention relates to the NAT technology of the communications field, relate in particular to a kind of method and system thereof of crossing medium-flow over network address conversion.

Background technology

IMS is the subsystem of the support IP multimedia service of 3G (Third Generation) Moblie partnership proposition.IMS uses SIP to call out controlling mechanism various types of multimedia services of creating, manage and terminate.This multimedia communication is not only simple video and audio communication, also comprises instant message, with the business that browse the location, collaborative work, Streaming Media or the like business, particularly new traffic mode and traditional voice merge, and we can say that IMS provides the basis of integrated services.

The important feature of IMS is the extensive adaptability to various access technologies.The IMS of 3GPP proposition at present can support the mobile access way of 2G and 3G, because the independence of IMS and access technology, standardization body such as 3GPP and ITU-T all expands the ability of IMS in research, to adapt to fixed terminal the different of terminal that relatively move aspect call flow and the authentication capability, the ability of enhancing aspect access security and QoS, support comprises the multiple access technology of fixed network, the common core network that structure fixed network and mobile network merge.

Because the scarcity of current public network address, a large number of users that current network is used are to use private net address,, need to solve network address translation NAT problem in order to enlarge the range of application of IMS network.Present widely used NAT switch technology comprises following several:

1, NAT/ALG mode

A common NAT device process IP head and TCP/UDP head are not handled the data of carrying, and the NAT/ALG mode need be handled the IP address information in the message payload, shows as Fig. 1.Significant disadvantages of NAT/ALG mode is the message content that can not discern after the encryption, transmits so must guarantee that message adopts expressly, and this makes message that very big potential safety hazard be arranged when transmitting in public network.

2, MIDCOM mode

As shown in Figure 2, different with NAT/ALG is, the frame structure of MIDCOM is the mechanism that adopts believable third party (MIDCOM Agent) that Middlebox (NAT/FW) is controlled, the intelligence of applied business identification is also transferred on the outside MIDCOM Agent by Middlebox, so application protocol is transparent to Middlebox.

3, STUN mode

Private network inserts the user and obtains the external address of its address correspondence on outlet NAT in advance by certain mechanism, just directly fill in the external address that exports on the NAT in the address information described in the message load then, rather than the interior user's of private network private IP address, content in the message load just need not to be modified through NAT the time like this, only need to get final product by the IP address of common NAT flow process conversion heading, the IP address information in the load is again consistent with the heading address information.

The service that exists a large amount of private users need use the IMS system to provide in the existing network, present scheme comprise that signaling network address transition NAT passes through with medium NAT and pass through two parts that basic networking as shown in Figure 3.

For the signaling passing through NAT, Border Gateway Function BGF (or claims Policy Enforcement Function, be policy enforcement function PEF) simply serve as NAT device, when private user is registered, this user signaling passage is distributed in BGF curing, the Signalling exchange that is used for follow-up terminal use and IMS system, mainly handling process is as shown in Figure 4:

Step 400: private user UE1 initiates registration REGISTER message, and this message arrives BGF by private network.

Step 401:BGF receives REGISTER message, judges that by destination address this message need send to the P-CSCF on the public network, sets up interim mapping channel (distribution network side address and port), gives P-CSCF with the message forward pass.

Step 402:P-CSCF judges that the request registration user is a private user, then by the interface between P-CSCF and the BGF, BGF is distributed to this user signaling passage (network side address and port) temporarily be handed down to BGF, require BGF to solidify this user signaling passage, be used for the Signalling exchange of follow-up this private user and P-CSCF.

After step 403:BGF finishes the signalling path cured, result is sent to P-CSCF by the interface between P-CSCF and the BGF (the same).

After step 404:P-CSCF receives the BGF response, finish follow-up register requirement and handle, REGISTER message forward pass; Finished passing through of signaling NAT this moment.

And, need P-CSCF to be handed down to BGF with carrying medium stream information in the session signaling for the medium passing through NAT, and the medium mapping channel when being used to set up session is an example with the INVITE in the IMS system, idiographic flow is shown in 5 figure:

Step 500: private user UE1 initiation session is set up request INVITE, and this message arrives BGF by private network.

The signalling path that solidifies when step 501:BGF registers by this user is given P-CSCF with the INVITE forward pass.

Step 502:, after P-CSCF receives INVITE, the Media Stream address and the port information that use during with the UE1 user conversation are handed down to BGF, the media channel when requiring BGF to set up user conversation (access side address, port and network side address and port that BGF distributes).

After step 503:BGF receives that request is set up in the medium mapping, Media Stream address and port information allocation medium mapping channel (access side address, port and network side address, the port of the corresponding BGF of each Media Stream) according to UE1 bring P-CSCF with processing response after finishing.

After step 504:P-CSCF received that success response is set up in medium mappings, the Media Stream address and the port information of SDP message body in network side address of distributing with BGF and the port substitute I NVITE request were then with the INVITE forward pass.Finish the initial creation of Calling Side user media mapping this moment.

Such scheme can go wrong when some scene, below is example with virtual LAN VLAN user's basic scene, as shown in Figure 6:

User UE1 belongs to different VLAN users with UE2, and there is the situation of address overlap in two users, different VLAN1 and the different physical interfaces access public networks of VLAN2 by BGF.Different VLAN users, pass through for signaling NAT and not have problems, this is because the network interface difference that different VLAN users insert by BGF, BGF can distribute different network side address or port, when signalling path solidifies, BGF can solidify it according to different network side address and ports, is used for the follow-up Signalling exchange of this user and network.

And pass through for medium NAT, because it is overlapping that the address of different user exists, according to aforementioned schemes, P-CSCF is handed down to the different VLAN users' of BGF medium mapping (enum) data can be identical, when then allocation medium is shone upon, BGF will not know to distribute the medium mapping of which VLAN right.If BGF is by there not being VLAN to determine that the medium mapping is right, although two VLAN user media passages can be with different group of addresses tag slots separately, but when session, the up Media Stream (mailing to network side from the UE side) that arrives BGF but can not determine to use which bar passage that Media Stream is forwarded.For other networks, when the address overlap of different user, also there is same problem.

Summary of the invention

The invention provides the method for a kind of crossing medium-flow over network address conversion, have the problem that correctly to transmit Media Stream when the different user address overlap to solve the medium mapping relations set up in the prior art.

The invention provides following technical scheme:

A kind of foundation is used for the method for the medium mapping relations of convert media stream, comprises the steps:

First network entity obtains the address information of the Media Stream that need to transmit, and sign and the described address information that can discern user place network send to Border Gateway Function BGF entity;

Described BGF entity is set up the medium mapping relations that are used to transmit Media Stream according to described address information, and binds described sign in these mapping relations.

Wherein, first network entity further obtains the service quality QoS information of the Media Stream that needs transmission, and described sign, address information and QoS information sent to second network entity of being responsible for the qos policy decision-making, second network entity generates corresponding qos policy, and described sign, address information and qos policy sent to described BGF entity, the BGF entity is related with the medium mapping relations of foundation with qos policy.

Described first network entity is the P-CSCF entity in the IMS network, and described second network entity is the SPDF/PDF entity in the IMS network; Being the Gq ' interface of expansion between P-CSCF entity and the SPDF/PDF entity, is the Ia interface of expansion between SPDF/PDF entity and the BGF entity.

First network entity obtains the relevant information of the Media Stream that needs transmission and sends to second network entity of being responsible for the qos policy decision-making, and described relevant information comprises address information and service quality QoS information;

Second network entity generates corresponding qos policy according to QoS information, and this qos policy and described address information are sent to the BGF entity;

The BGF entity is set up the medium mapping relations that are used to transmit Media Stream according to described address information, and described qos policy is related with these medium mapping relations.

Wherein:

Described relevant information further comprises the sign that can discern user place network, and described second network entity sends to the BGF entity with this sign, and the BGF entity will identify and the medium mapping relations binding of setting up.

By expanding the relevant information that existing interface between first network entity and second network entity transmits described Media Stream; Transmit described address information, qos policy and described sign by the existing interface of expanding between second network entity and the BGF entity.

First network entity is the P-CSCF entity in the IMS network, and described second network entity is the SPDF/PDF entity in the IMS network; Being the Gq ' interface of expansion between P-CSCF entity and the SPDF/PDF entity, is the Ia interface of expansion between SPDF/PDF entity and the BGF entity.

A kind of method of crossing medium-flow over network address conversion comprises the steps:

The Media Stream that the user is sent is sent to the Border Gateway Function BGF entity in the network;

Described BGF entity is according to discerning the sign of described user place network and the source address information in the Media Stream, and coupling is used to transmit Media Stream and port that bind the definite forwarding of the medium mapping relations Media Stream that the sign that can discern user place network is arranged; And

BGF transmits described Media Stream by the port of determining.

Wherein, described BGF entity carries out QoS control further according to the qos policy that is associated with the medium mapping relations to the Media Stream that utilizes these medium mapping relations to transmit.

A kind of network system comprises:

Subscriber equipment is used to receive and dispatch signaling and Media Stream;

First network entity is used to obtain the address information of the Media Stream that described subscriber equipment need transmit and can discerns the sign of user place network, and issues and set up the medium mapping relations that are used to transmit Media Stream;

Border Gateway Function BGF entity, the described address information and the foundation of described sign that are used for providing according to the network control entity are used to transmit the medium mapping relations of Media Stream and bind described sign, and when receiving the Media Stream of subscriber equipment transmission, mate described medium mapping relations with definite port of transmitting Media Stream according to the sign that can discern user place network and source address information, and transmit described Media Stream by this port.

Described network system also comprises:

Second network entity, be used to finish the QoS policy decision-making, receive the QoS information that first network entity obtains, generate corresponding qos policy and send to described BGF entity according to this QoS information, the BGF entity is related with corresponding medium mapping relations with it, and the Media Stream that utilizes these medium mapping relations to transmit is carried out QoS control.

Described first network entity by the expansion interface described address information, sign and QoS information are sent to second network entity, second network entity by the expansion interface with described address information and the sign transparent transmission to the BGF entity.

Beneficial effect of the present invention is as follows:

User bound place network of network sign when the present invention sets up the medium mapping relations be used to transmit Media Stream at border medium gateway function entity, when the Media Stream that follow-up forwarding user side sends, obtain to transmit the port of Media Stream by source address and network identity inquiry medium mapping relations, therefore, even the coupling that user's address overlap in the heterogeneous networks, border medium gateway function entity also can be correct is transmitted the medium mapping relations of Media Stream.

The QoS information of the medium that the present invention transmits as required generates corresponding qos policy and related with the medium mapping relations of setting up, utilize this qos policy that the Media Stream of transmitting by these medium mapping relations is carried out QoS control, thereby can fully guarantee the quality of service requirement of media stream; Simultaneously, the flow process of setting up the medium mapping relations is merged with the flow process that generates qos policy, simplified handling process, improved system effectiveness.

Description of drawings

Fig. 1 is the structural representation of packet in the prior art;

Fig. 2 is the frame structure schematic diagram of MIDCOM in the prior art;

Fig. 3 is the schematic network structure that the user uses the IMS business in the prior art by NAT;

Fig. 4 is a flow chart of realizing the signaling passing through NAT in the prior art;

Fig. 5 is for setting up the flow chart of medium mapping channel by conversation request INVITE in the existing IMS network;

Fig. 6 uses the schematic network structure of IMS business for VLAN user in the prior art;

Fig. 7 A is a binding VLAN tag system structural representation in the medium mapping relations that are implemented in the embodiment of the invention among the BGF;

Fig. 7 B is a flow chart of setting up user ID and the binding of VLAN sign in the embodiment of the invention by registration process;

Fig. 8 is for setting up the flow chart of medium mapping relations when the user sets up session in the embodiment of the invention;

Fig. 9 is the system schematic that quality control was set up and served to the support media mapping relations in the embodiment of the invention;

Figure 10 is for setting up the flow chart that medium shine upon and issue the service quality control strategy in the embodiment of the invention;

Figure 11 is the system schematic of multi-level NAT scene in the embodiment of the invention;

Figure 12 dynamically obtains the system schematic of vlan information for realizing BGF in the embodiment of the invention.

Embodiment

The transmission problem that causes Media Stream in order to solve the different user address overlap, the present invention's binding when foundation is used to transmit the Media Stream mapping relations of Media Stream can be discerned the sign of user place network.Further, when follow-up forwarding Media Stream, the marking matched described Media Stream mapping relations of utilizing the source address in the Media Stream and can discerning user place network determine to transmit the port of medium.

Present embodiment mainly uses the IMS business to be elaborated as example with the virtual LAN VLAN user, and wherein, the sign that can discern user place network adopts the VLAN sign.

Consult shown in Fig. 7 A, the user of different VLAN is linked into border networks function BGF (or title Policy Enforcement Function, i.e. policy enforcement function PEF) by different physical ports, and BGF serves as network address translation device.When VALN user registered, this user signaling passage was distributed in BGF curing, is used for the Signalling exchange of follow-up terminal use and IMS system.

In the present embodiment,, when the user registers, set up the binding relationship of the VLAN sign of user and place vlan network, set up the medium mapping relations binding that BGF identifies VLAN and set up in the process in subsequent session by the interface between expansion P-CSCF and the BGF.Because different VLAN users insert BGF by different physical interfaces, BGF can distinguish user's VLAN sign according to physical interface.BGF mates described medium mapping relations with definite port of transmitting Media Stream according to VLAN sign and source address information, and transmits described Media Stream by this port when receiving the Media Stream of VLAN user's transmission.

Consult shown in Fig. 7 B, when the user registered, the handling process that the Proxy Call Session Control Function P-CSCF in the IMS system sets up user and VLAN ID binding relationship was as follows:

Step 700:VLAN user UE1 initiates registration REGISTER, and this message arrives BGF by VLAN.

Step 701:BGF receives REGISTER message, because different VLAN insert BGF by different physical interfaces, can set up interim signalling path for the IP address and the port of UE1 user's distribution network side by interface message BGF, will register REGISTER request forward pass after finishing and give P-CSCF.

Step 702:P-CSCF judges that the request registration user is a private user, then by the interface between P-CSCF and the BGF, BGF is distributed to this user signaling passage (network side address and port) temporarily be handed down to BGF, require BGF to solidify this user signaling passage, be used for the Signalling exchange of follow-up this private user and P-CSCF.

After step 703:BGF successfully handled and solidifies request, the VLANID that UE1 user place VLAN is netted brought P-CSCF by response message.

After step 704:P-CSCF receives BGF response, preserve the incidence relation of this user and VLAN ID, be used for the follow-up foundation of medium NAT when setting up session. after finishing follow-up register requirement processing, P-CSCF is with REGISTER message forward pass.Finished passing through of VLAN subscriber signaling NAT this moment.

Consult shown in Figure 8ly, when VLAN user set up session, the binding relationship of this user and VLAN ID was set up the medium mapping relations when using registration, and its handling process is as follows:

UE1 among the step 800:VLAN sends session and sets up request INVITE, and the Media Stream relevant information that needs during user conversation is carried by the SDP message body in the INVITE, and this request arrives BGF by VLAN.

The signalling path that solidifies when step 801:BGF registers by this user is given P-CSCF with the INVITE forward pass.

After step 802:P-CSCF receives INVITE, medium relevant information during with the UE1 session is handed down to BGF, medium mapping when being used for BGF and setting up user conversation, VLAN ID with user binding when simultaneously P-CSCF will register is handed down to BGF, is used for the different VLAN user of BGF differentiation and sets up medium and shine upon.

Medium stream information (IP address and port) with the UE1 related VLAN ID of step 803:BGF during according to the UE1 session, the medium mapping when setting up session is right, gives P-CSCF by response message with this information band.

The Media Stream address and the port of SDP message body forward to callee side with INVITE then in network side address that step 804:P-CSCF distributes with BGF and the port substitute I NVITE request.Finish the initial creation (finish session set up may through repeatedly mutual) of Calling Side user media mapping this moment.

Step 805, UE1 send Media Stream.

Step 806, BGF receive VLAN sign and the source address information of extracting the user behind the Media Stream, and mate determining to transmit port with the medium mapping relations, and the port of determining sends Media Stream.

When session need be done QoS control, this moment, scene saw also shown in Figure 9.In this scene, different VLAN inserts by the different physics mouth of BGF, and P-CSCF and BGF solidify signalling path by internal interface (using the COPS agreement), because this interface does not have standard, may realize cancelling after the Xin Lingdaili function at BGF.The QoS of customer requirements service is by finishing alternately between P-CSCF, SPDF, the BGF, between P-CSCF and the SPDF between interface, SPDF and the BGF interface be standard Gq ' and Ia interface.

Present embodiment merges in the QoS flow process foundation of medium NAT mapping, and promptly by expansion Gq ', Ia interface, support media NAT mapping is set up and QoS control.VLAN user's register flow path is with aforementioned description in this scene, and the foundation of signalling path is finished by BGF oneself, and the curing of signalling path is finished by internal interface between P-CSCF and the BGF.After BGF realized the Xin Lingdaili function, this interface can be cancelled.For the session flow process, to set up the medium mapping of session to unifying, by Gq ' interface between expansion P-CSCF and the SPDF and the Ia interface between SPDF and the BGF, when issuing the QoS control strategy at BGF with two flow processs of enforcement qos policy, also handle medium NAT mapping, thereby simplify flow process.Consult shown in Figure 10ly, the process of setting up the medium mapping relations is as follows:

UE1 among the step 1000:VLAN sends session and sets up request INVITE, and the Media Stream relevant information that needs during user conversation is carried by the SDP message body in the INVITE, and this request arrives BGF by VLAN.

The signalling path that solidifies when step 1001:BGF registers by this user is given P-CSCF with the INVITE forward pass.

The VLAN ID of the address of step 1002:P-CSCF required Media Stream during with the UE1 user conversation and port information, QoS information, the binding when user registers passes through BGF for strategy decisive function SPDF based on service, SPDF by the Gq ' interface of expansion and distinguishes different VLAN users and set up the medium mapping and specify qos policy.

After step 1003:SPDF received request, according to the strategic decision-making that local policy calculates final control QoS resource, Media Stream address during with strategic decision-making information, UE1 user conversation and information such as port information, VLANID were handed down to BGF by the expansion Ia interface.

Media Stream address and the port information, when VLAN id information set up session medium mapping channel of step 1004:BGF during according to the UE1 user conversation, implement the qos policy that SPDF issues simultaneously, after finishing result is uploaded to SPDF equipment by the expansion Ia interface.

Step 1005:SPDF passes through P-CSCF by expansion Gq ' interface with the medium map information after finishing follow-up QoS processing.

The Media Stream address and the port of SDP message body forward to callee side with INVITE then in network side address that step 1006:P-CSCF distributes with BGF and the port substitute I NVITE request.Finish the initial creation of Calling Side user media mapping this moment.

Step 1007: after callee side returned 183 responses, P-CSCF judges needed previous medium mapping and the QoS information of setting up of change, then passes through Gq ' interface notice SPDF change.As having set up the mapping relations of transmitting audio stream and video flowing earlier, only transmit audio stream after through consultation, then the mapping relations of video flowing are transmitted in the notice deletion.And for example, the QoS information after the negotiation changes with QoS information formerly, need regenerate qos policy this moment and notify BGF change.

Qos policy after step 1008:SPDF then will change and medium map information are handed down to BGF by the expansion Ia interface.

Step 1009:BGF echoes and should give SPDF after finishing change medium map information.

Step 1010:SPDF passes through P-CSCF with the medium map information.

Behind the medium map information, give user UE1 in the step 1011:P-CSCF change INVITE body with the message forward pass.

In step 1007, P-CSCF judges when not needing to change mapping relations and QoS information, then no longer carries out step 1008 to step 1011.

The foundation of above-mentioned medium NAT mapping and the fusion of QoS flow process are equally applicable to the application scenarios that other need finish NAT mapping and QoS control, and are not limited only to can not correctly transmit in the application of medium to prevent the different user address overlap by binding VLAN.

Said method is equally applicable to the scene that has multi-level NAT shown in Figure 11.In this scene, the foundation of VLAN subscriber signaling and media channel is fully with aforementioned scheme, for medium NAT, the

NAT device

1,2 of middle cascade only serves as nat feature, can not change the Media Stream address and the port message of signaling message body, therefore, P-CSCF is handed down to the Media Stream address of BGF and the information that port remains former UE1, and BGF sets up the medium mapping channel in view of the above.

Consult shown in Figure 12, when different VLAN inserts BGF by same physical interface, BGF dynamically obtains vlan information, for example comprise the VLAN sign the IP head of the packet of coming from SWITCH, be used to indicate this bag from which VLAN net, when the same physics mouth of BGF was received the packet that contains different VLAN signs, BGF can set up different NAT mappings in view of the above and distinguish different VLAN.When the packet of network side was dealt into different network side address of BGF or port, BGF can add corresponding VLAN sign back forward pass and give SWITCH in the IP head, and SWITCH can correctly be distributed to the user with bag in view of the above.Therefore, previously described VLAN user's registration and session flow process are suitable for scene shown in Figure 12 equally.

Sign for difference user place network is not limited to network identity, also network segment information etc.

Though present embodiment uses the IMS business to describe as example with VLAN user, but be not limited to this, said method is equally applicable to other Media Streams of the different terminals of address overlap and handles, for example, the address overlap user need do QoS control, the perhaps overlapping user's of inquire address application such as physical location information.

Obviously, those skilled in the art can carry out various changes and modification to the present invention and not break away from the spirit and scope of the present invention.Like this, if of the present invention these are revised and modification belongs within the scope of claim of the present invention and equivalent technologies thereof, then the present invention also is intended to comprise these changes and modification interior.

Claims

1, a kind of foundation is used for the method for the medium mapping relations of convert media stream, it is characterized in that, comprises the steps:

2, the method for claim 1 is characterized in that, obtains the sign that can discern user place network when the user registers.

3, the method for claim 1 is characterized in that, described network identity or the address field information of being designated.

4, the method for claim 1, it is characterized in that, first network entity further obtains the service quality QoS information of the Media Stream that needs transmission, and described sign, address information and QoS information sent to second network entity of being responsible for the qos policy decision-making, second network entity generates corresponding qos policy, and described sign, address information and qos policy sent to described BGF entity, the BGF entity is implemented this qos policy.

5, method as claimed in claim 4 is characterized in that, described described address information of the second network entity transparent transmission and sign.

6, as claim 4 or 5 described methods, it is characterized in that, by expanding the relevant information that interface between first network entity and second network entity transmits described Media Stream; Transmit described address information, qos policy and described sign by the interface of expanding between second network entity and the BGF entity.

7, method as claimed in claim 6 is characterized in that, first network entity is the P-CSCF entity in the IMS network, and described second network entity is the SPDF/PDF entity in the IMS network; Being the Gq ' interface of expansion between described P-CSCF entity and the SPDF/PDF entity, is the Ia interface of expansion between described SPDF/PDF entity and the BGF entity.

8, a kind of foundation is used for the method for the medium mapping relations of convert media stream, it is characterized in that, comprises the steps:

The BGF entity is set up according to described address information and is used to transmit the medium mapping relations of Media Stream, and implements described qos policy.

9, method as claimed in claim 8, it is characterized in that, described relevant information further comprises the sign that can discern user place network, and described second network entity sends to the BGF entity with this sign, and the BGF entity will identify and the medium mapping relations binding of setting up.

10, method as claimed in claim 9 is characterized in that, first network entity obtains the sign that can discern user place network in user registration course.

11, method as claimed in claim 9 is characterized in that, described described address information of the second network entity transparent transmission and sign.

12, method as claimed in claim 11 is characterized in that, described network identity or the address field information of being designated.

13, as each described method of claim 8 to 12, it is characterized in that, by expanding the relevant information that existing interface between first network entity and second network entity transmits described Media Stream; Transmit described address information, qos policy and described sign by the existing interface of expanding between second network entity and the BGF entity.

14, method as claimed in claim 13 is characterized in that, first network entity is the P-CSCF entity in the IMS network, and described second network entity is the SPDF/PDF entity in the IMS network; Being the Gq ' interface of expansion between P-CSCF entity and the SPDF/PDF entity, is the Ia interface of expansion between SPDF/PDF entity and the BGF entity.

15, a kind of method of crossing medium-flow over network address conversion is characterized in that, comprises the steps:

Described BGF entity is according to discerning the sign of described user place network and the source address information in the Media Stream, and the coupling binding has the medium mapping relations of the sign that can discern user place network to determine to transmit the port of Media Stream; And

BGF transmits described Media Stream by the port of determining.

16, method as claimed in claim 15 is characterized in that, is sent to BGF after the described Media Stream process multistage network address transition.

17, method as claimed in claim 15 is characterized in that, BGF determines described sign according to the physical port that the user inserts; Perhaps BGF extracts described sign dynamically from Media Stream.

18, as each described method of claim 15 to 17, it is characterized in that described network identity or the address field information of being designated.

19, a kind of network system is characterized in that, comprising:

20, network system as claimed in claim 19 is characterized in that, also comprises:

Second network entity is used to finish the QoS policy decision-making, receives the QoS information that first network entity obtains, and generates corresponding qos policy and sends to described BGF entity according to this QoS information, and the BGF entity is further implemented qos policy.

21, network system as claimed in claim 20, it is characterized in that, first network entity by the expansion interface described address information, sign and QoS information are sent to second network entity, second network entity by the expansion interface with described address information and the sign transparent transmission to the BGF entity.

22, network system as claimed in claim 21 is characterized in that, first network entity is the P-CSCF entity in the IMS network, and described second network entity is the SPDF/PDF entity in the IMS network; Being the Gq ' interface of expansion between P-CSCF entity and the SPDF/PDF entity, is the Ia interface of expansion between SPDF/PDF entity and the BGF entity.