CN1878136A - Method for recognizing multiple emulation service flow path - Google Patents

Abstract

A method for identifying multiple simulated service flow paths, comprising: when configuring an attached circuit N TO 1 mode PW binding command, setting an AC-id item for identifying a specific sub-attached circuit (AC) service; sending a notification message The AC-id field and the corresponding forwarding index are added in the AC-id field. When the opposite end receives the notification message, it searches for the matching (corresponding) sub-AC according to the AC-id. , the hardware forwarding entry is issued to forward the service message, otherwise the service message is not forwarded. The present invention can accurately know the information of the simulated service pair through the AC-id, rejects the PW UP caused by the AC UP not belonging to the same simulated service pair, makes the PW state strictly consistent with the real forwarding state, and avoids the service transmission that cannot be finally intercommunicated It wastes processing resources of nodes along the way and precious network bandwidth resources; at the same time, using the forwarding index field of AC-id instead of the VPI/VCI field to specifically identify a PVC for forwarding can improve the forwarding speed.

Description

A Method for Identifying Multiple Simulated Service Flow Paths

technical field

The invention relates to the field of communication technology, in particular to a method for identifying multiple simulated service flow paths based on PWE3 (Pseudo-WireEmulation Edge-to-Edge end-to-end pseudo-wire emulation).

Background technique

At present, when operators provide multiple services, they basically adopt a parallel or "overlapping" approach: build and maintain multiple networks, and use different access devices for each different service at the presentation point. In addition to making network planning more complicated, it is also expensive both in terms of construction costs and operating costs. Therefore, when providing multiple services, in order to reduce construction and operation costs, operators hope to find a method that can provide multiple services on a public packet switching network (PSN).

In order to provide a unified multi-service network platform, the IETF started the standardization work of "X over PSN" for transmitting any service on a packet-switched network, and named it end-to-end pseudo-wire emulation (Pseudo-Wire Emulation Edge-to- Edge, abbreviated as PWE3).

The implementation of emulation services on packet-switched networks can be divided into two types: one PSN carries only one emulation service flow (1 TO 1 mode) and one PSN carries multiple emulation service flows (N TO 1 mode). The benefit of carrying multiple emulation service flows in one PSN is that PW (pseudowire) headers can be used more effectively.

The establishment of a PW is the result of mutual negotiation between the PEs (Provider Equipment) at both ends, so the PEs at both ends need to exchange the local PW forwarding status. The forwarding state of the local PW depends on the state of the AC service that needs to be simulated, the state of the LDP session (LDP session) of the remote PE, and the state of the outer tunnel carrying the pseudowire service. In the N TO 1 mode, the status of the AC (Attachment Circuit) service depends on the sum of the N sub-AC states corresponding to the PW (in the network model of the protocol, multiple sub-ACs of the same PW are simultaneously bound in the N TO 1 mode. A PVC (Permanent Virtual Connect) is collectively referred to as an AC. This invention complies with the terminology in the protocol network model, but for the convenience of explanation, a PVC in an AC under NTO 1 mode is called an "AC" of this AC. Sub-AC"): If among the sub-ACs corresponding to the PW, the last sub-AC whose status is UP (normal working status) goes down (abnormal working status), the status of the AC is DOWN; all sub-ACs corresponding to the PW If the first child AC is UP, the AC status is UP. There are two notification methods: Martini notification and extended Notification notification.

1. Martini notification:

Referring to Figure 1, the status of the AC, the status of the 1dp session of the remote PE, and the status of the outer tunnel are all up at the same time, then the forwarding status of the local PW is forwardable, and a Mapping message is sent; if one of the three is down, Then the forwarding state of the local PW is non-forwarding. At this time, a Withdraw message should be sent to withdraw the inner label. For example: in the case of PW UP, as long as the AC is DOWN, the forwarding state of the local PW is non-forwarding, and a Withdraw message is sent to remove the protocol.

2. Notification notification:

After sending the Mapping interaction inner label, as long as the configuration is not deleted, the protocol will not be removed, and only the Notification message will be sent to exchange the local PW status of both parties. For example: in the case of PW UP, as long as the AC is DOWN, the forwarding status of the local PW is non-forwarding, but at this time, no Withdraw message is sent to remove the protocol, but a Notification message is sent to inform the other party that the forwarding status of the local PW is It cannot be forwarded (realized by notifying the forwarding code of the local PW), and the inner label is reserved. As shown in the figure, the Notification message contains the status code of the local PW.

In the Martini mode, whether to send a Mapping (label mapping) message for exchanging inner labels depends on the status of the AC, the session status of the peer PE, and the status of the outer tunnel. And as long as the state of the AC, the state of the session of the peer PE, and the state of the outer layer tunnel all go down, a Withdraw message is sent to withdraw the inner layer label. However, after configuration in the Notification mode, as long as the session status with the peer PE is Up, regardless of the status of the AC or the status of the outer tunnel, a Mapping message for exchanging the inner label will be sent. When the status of the AC or the status of the outer tunnel is DOWN, only the local PW status code is updated, and the local PW status code is reported to the peer PE through the Notification message. The main difference from the Martini method is that as long as the configuration is not deleted, it The protocol will not be removed to reclaim the inner layer label, but a Notification message will be sent to inform the local PW that the forwarding status is not forwardable. When the next UP occurs, there is no need to redistribute the label, and the Notification message will be sent to inform the local PW that the forwarding status is not forwardable. Forward.

The Notification method in the prior art has a great advantage over the Martini method in that it can reduce the exchange of messages between PEs. However, they have a common shortcoming that they cannot announce the information of a specific AC service pair. As shown in Figure 3, subAC1-subAC3 and subAC2-subAC4 are two service flows respectively, and the pseudo-wire PW1 is multiplexed in N TO 1 mode. subAC1 and subAC2 are respectively connected to different ports of PE1, and the states of the two are combined to form the AC state on PE1. The subAC3 and subAC4 are respectively connected to different ports of PE2, and the states are combined to form the AC state at PE2. At PE1, when the state of the LDP session with the remote PE is UP and the state of the outer tunnel is UP, if the state of subAC1 changes from DOWN to UP, the state of the AC at PE1 is UP, and the forwarding state of the local PW is forwardable. state, or send a Mapping packet, or send a Notification packet to notify the local PW status is UP. At PE2, when the session state with the peer PE and the state of the outer tunnel are both UP, if the state of subAC4 changes from DOWN to UP, the AC state at PE2 is UP, and the forwarding state of the local PW of PE2 is also forwardable. Status, because the forwarding status of the local and remote PWs is forwardable, the status of this PW is UP, and the logical forwarding entry is issued. However, the actual situation is that subAC1 and subAC3 are a service pair. Therefore, after the service information of subAC1 reaches PE2 through PW1, the service packets of subAC1 will still be discarded by PE2 because the state of subAC3 is DOWN. It can be seen that, in this situation, neither the Martini method nor the Notification method can notify the correct service pair information of the AC. After the service information of subAC1 reaches PE2 through PW1, it cannot be finally forwarded to the destination, which unnecessarily increases the number of nodes along the route. processing burden, more importantly, a waste of valuable network bandwidth resources.

In the prior art, for the specific packet encapsulation format of the PW service in the NTO 1 mode, the encapsulation frame format of the NTO 1 packet of ATM is used as an example to make a specific description, and the encapsulation of other services is basically similar. Use the encapsulation formats shown in Figures 4 and 5 to encapsulate the N TO 1 ATM PW message frame, and distinguish the specific AC through the vpi/vci carried in the message. The protocol stipulates that the VPI/VCI values of PVCs from different ports must be different. However, in practical applications, this is difficult to guarantee. Therefore, it is necessary to use outvpi/outvci to convert the VPI/VCI value of the PVC from each port to be globally unique. When receiving the N TO 1 ATM PW message frame, use outvpi/outvci to find the specific PVC, and process different services separately.

The limitations of the existing methods are:

1) In this way, the values of outvpi/outvci and inputvpi/inputvci corresponding to the outbound direction of the PW are not necessarily the same, so the binding commands of PW and PVC need to be configured in both the inbound and outbound directions:

a.PVC+PW+outvpi/outvci

b.inputvpi/inputvci+PW+PVC

This increases the complexity of user configuration.

2) The hardware implementation is relatively complicated, and the search efficiency is low. For the inbound direction, you need to obtain the corresponding PVC according to the inputvpi/inputvci in the packet. The range of vpi/vci is 12 bits/16 bits respectively, but since the number of PVCs supported by general equipment is far less than 2 to the 28th power, HASH is required to complete the mapping on the hardware.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the problem that the PW state is UP when the AC of the non-service pair is UP due to the inability to notify the correct service pair message of the AC in the prior art, but the PW cannot actually forward the message, resulting in that even if the AC information at one end The PE that reaches the other end through the PW pseudowire cannot be forwarded, but is discarded by the PE, thus wasting the processing resources of the nodes along the way and the precious network bandwidth resources. This provides a protocol optimization in N TO 1 mode. The method is to accurately obtain the simulated service pair information, and make the PW state consistent with the real forwarding state.

The technical scheme that the present invention adopts for solving the problems of the technologies described above is:

A method for identifying multiple simulated service flow paths, the method comprising:

A. Configure multiple service flows of the auxiliary circuit to share a pseudo-wire binding command in the form of an artificial line, and set the auxiliary circuit identifier used to identify the service of the auxiliary auxiliary circuit;

B. The first end of the pseudowire sends a notification message with the first attached circuit identifier field;

C. The second end of the pseudowire receives the notification message, and searches for a second sub-attachment circuit having the same identifier field of the first adjunct circuit according to the adjunct circuit identifier;

D. When both the second sub-attachment circuit and the pseudowire are in normal working state, issue a hardware forwarding entry and forward the service message, otherwise, do not forward the service message.

The method described above, wherein the notification message includes: a normal notification message and an abnormal notification message.

The method, wherein, the step B specifically includes:

When the state of the first sub-attachment circuit at the first end of the pseudowire changes from an abnormal working state to a normal working state, the first service provider equipment at the end sends a normal message; the normal message carries a sub-attachment The identifier of the circuit and the corresponding forwarding index.

The method, wherein, the step C specifically includes:

After receiving the normal notification message, the second service provider device at the second end of the pseudowire searches for a second sub-attachment circuit with the same first adjunct circuit identification field according to the adjunct circuit identifier.

The method, wherein, the step D specifically includes:

When the state of the second sub-accessory circuit is a normal working state, judging the state of the pseudo wire;

If the pseudowire is in the normal working state, set the state of the first terminal auxiliary circuit in the data structure of the second service provider's equipment to the normal working state, and issue the hardware forwarding entry, and start forwarding the service message;

If the pseudowire is in an abnormal working state, set the state of the first sub-attachment circuit in the data structure of the second service provider equipment to be in a normal working state.

The method, wherein, the step D also includes:

When the state of the second sub-auxiliary circuit is in the abnormal working state, set the state of the first terminal auxiliary circuit in the data structure of the second service provider equipment to the normal working state.

The method described above, wherein, when the state of the last sub-attached circuit at the first end of the pseudowire changes from a normal working state to an abnormal working state, the first service provider device at the end sends a message notifying the abnormality; the Notify that the abnormal message carries the identifier of the sub-attached circuit.

Described method, wherein, described step C also comprises the step:

When the second service provider device at the second end of the pseudowire receives the abnormal notification message, it searches for a second sub-attachment circuit having the same first sub-attachment circuit identification field according to the adjunct circuit identifier.

The method, wherein, the step D specifically includes:

When the state of the second sub-accessory circuit is a normal working state, it is judged whether the state of the pseudo wire is normal;

When the pseudowire is in the normal working state, the state of the first sub-affiliated circuit in the data structure of the second service provider equipment is set to the abnormal working state and the hardware forwarding entry is deleted;

Otherwise, only the state of the first sub-accessory circuit in the data structure of the second service provider equipment is set as an abnormal working state.

The method described above, wherein the pseudowire encapsulation message format in which multiple service flows share one simulated circuit is adjusted, and the forwarding index field corresponding to the attached circuit identifier is used to replace the virtual path identifier/virtual channel identifier field, and the index identifies a permanent Virtual connection.

The method, wherein: the method also includes:

Determine whether the inner label of the pseudowire has been allocated; if the labels of the pseudowire at both ends of the service provider equipment have been allocated, the status of the pseudowire is the normal working status; otherwise, the status of the pseudowire is the abnormal working status.

The beneficial effects of the present invention are: the simulated service pair information can be accurately obtained through the AC-id, and the PW UP caused by the AC UP not belonging to the same simulated service pair is rejected, so that the PW state is strictly consistent with the real forwarding state, avoiding failure The final intercommunication service transmission wastes the processing resources of nodes along the way and precious network bandwidth resources, and the service configuration command for binding AC and PW in N TO 1 mode is simple, and the configuration amount is only half of the previous one; at the same time, due to the use of AC-id forwarding The index forwarding index field replaces the VPI/VCI field to specifically identify a PVC for forwarding, so the hardware implementation is relatively simple, and the information of the specific PVC can be determined by linearly searching the index corresponding to the AC-id, thereby improving the forwarding speed.

Description of drawings

Figure 1 is a schematic diagram of a network notified in Martini mode;

Fig. 2 is a schematic diagram of a network notified in the Notification mode; Fig. 3 is a schematic diagram of a PW network in the prior art NTO1 mode;

Fig. 4 is a schematic diagram of the prior art N TO 1 ATM PW message frame encapsulation format;

FIG. 5 is a schematic diagram of a specific encapsulation format of an N TO 1 ATM PW message frame in the prior art;

Fig. 6 is a schematic diagram of the PW network under the NTO 1 mode of the present invention;

Fig. 7 is a network reference model diagram under the NTO1 mode of the present invention;

Fig. 8 is a schematic diagram of the specific encapsulation format of the N TO 1 ATM PW message frame of the present invention.

Detailed ways

Below according to accompanying drawing and embodiment the present invention will be described in further detail:

The present invention mainly relates to the protocol realization of the NTO 1 mode of emulation business on the packet switching network, including the following content: when configuring the PW binding command of the ACNTO 1 mode, setting the AC-id (attached to identify the specific sub-AC business) circuit identifier) configuration item; add the AC-id field and the corresponding forwarding index in the sending Notification (notification) message, when the peer end receives the Notification message and searches for the matching (corresponding) sub-AC according to the AC-id, only When both ACs and PWs in a service flow pair are UP, the hardware forwarding entry is issued and service packets are forwarded; otherwise, the service packets are not forwarded. The specific method is as follows:

1. When configuring the NTO 1 PW binding command of the AC, add the AC-id configuration item to identify the specific sub-AC service pair. As shown in FIG. 6 , for example, an AC-id equal to 1 is allocated to the subAC1-subAC3 service pair, and an AC-id equal to 2 is allocated to the subAC2-subAC4 service pair.

2. Add the AC-id field and the corresponding forwarding index in the Notification message sent, and notify the peer PE of the status of the specific sub-AC at the local end through the AC-id. .

Referring to Figure 6 and Figure 7, when the state of the first sub-AC (assumed to be subAC1) of all sub-ACs at the PW end (such as PE1 end) changes from DOWN to UP, PE1 sends a NotificationUP message, which carries the sub-AC The AC-id of the AC and the corresponding forwarding index. After receiving the Notification UP message, the peer PE2 searches for the matching sub-AC service (subAC3). If the service status of the PE2 terminal AC (subAC3) is DOWN, set the status of the peer terminal AC (subAC1) in the PE2 data structure to UP. If the service status of the terminal AC (subAC3) on PE2 is also UP, and the status of the PW is UP, then set the status of the terminal AC (subAC1) in the PE2 data structure to UP and issue a hardware forwarding entry to start forwarding service packets; if If the status of PW is DOWN, only the status of terminal AC (subAC1) in the PE2 data structure is set to UP. When the state of the last sub-AC (assumed to be subAC1) of all sub-ACs on the PW side (such as PE1 side) changes from UP to DOWN, a Notification DOWN message is sent, and the message carries the AC-id of the sub-AC. After receiving the Notification DOWN message, the peer PE2 searches for the matching sub-AC service (subAC3). If the service status of the terminal AC (subAC3) on PE2 is UP and the status of the PW is UP, the peer terminal AC (subAC1) in the PE2 data structure The state of the terminal AC (subAC1) in the PE2 data structure is set to DOWN and the hardware forwarding entry is deleted. In this way, the PE can also clearly know the PW status, the AC status of the local terminal and the AC status of the opposite terminal in a service flow pair.

In the present invention, the state of the PW is strictly distinguished from the state of the sub-AC service. It is agreed that if the labels of the PWs at both ends of the PE have been allocated (both the label mapping message is sent to the peer and the label mapping message is received from the peer), the state of the PW is UP; otherwise, the state of the PW is DOWN. In this way, the state of the PW is independent of the state of the AC, the state is more clearly distinguished, the understanding and implementation of the protocol are clearer, and it is more in line with the protocol "(draft-ietf-pwe3-control-protocol-14.txt") The understanding of PW in the specified PWE3Reference Model, that is, the state of PW should be independent of the state of AC.

3. Adjust the encapsulation format of PW message frame in N TO 1 mode

Referring to Fig. 8, take the adjustment of the PW message frame encapsulation format of the N TO 1 mode of ATM as an example to illustrate our adjustment scheme for the N TO 1 mode PW encapsulation message format. Remove the VPI and VCI fields in the encapsulation format of the N TO 1 ATM PW message frame, and use the forwarding index field corresponding to the AC-id to specifically index a PVC. After receiving the N TO 1 ATM PW message frame, search for the corresponding PVC according to the forwarding index corresponding to the AC-id, which can not only make the search reach a linear speed, but also reduce the complexity of hardware implementation. The same is true for the adjustment of the NTO 1 encapsulation format of other pseudowire services. For example, for FR emulation services, the forwarding index field corresponding to the AC-id is also used to index a specific FR service flow.

It can be seen from the above that the present invention introduces the mechanism of the sub-service number, so that the PE device can distinguish the specific AC service pair, without causing the PW state UP caused by the AC UP of the non-service pair, but it cannot really forward The status of the message. Moreover, through this mechanism, it is also possible to avoid the problem that the efficiency of finding the corresponding PVC through the inputvpi/inputvci hardware is not high.

It can be understood that those skilled in the art can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention, and all these changes or replacements should belong to the protection scope of the appended claims of the present invention.

Claims (11)

1. A method for identifying multiple simulated service flow paths, the method comprising: A. Configure multiple service flows of the auxiliary circuit to share a pseudo-wire binding command in the form of an artificial line, and set the auxiliary circuit identifier used to identify the service of the auxiliary auxiliary circuit; B. The first end of the pseudowire sends a notification message with the first attached circuit identifier field; C. The second end of the pseudowire receives the notification message, and searches for a second sub-attachment circuit having the same identifier field of the first adjunct circuit according to the adjunct circuit identifier; D. When both the second sub-attachment circuit and the pseudowire are in normal working state, issue a hardware forwarding entry and forward the service message, otherwise, do not forward the service message. 2. The method according to claim 1, wherein the notification message includes: a normal notification message and an abnormal notification message. 3. The method according to claim 2, wherein the step B specifically comprises: When the state of the first sub-attachment circuit at the first end of the pseudowire changes from an abnormal working state to a normal working state, the first service provider equipment at the end sends a normal message; the normal message carries a sub-attachment The identifier of the circuit and the corresponding forwarding index. 4. The method according to claim 3, wherein the step C specifically comprises: After receiving the normal notification message, the second service provider device at the second end of the pseudowire searches for a second sub-attachment circuit with the same first adjunct circuit identification field according to the adjunct circuit identifier. 5. The method according to claim 4, wherein said step D specifically comprises: When the state of the second sub-accessory circuit is a normal working state, judging the state of the pseudo wire; If the pseudowire is in the normal working state, set the state of the first terminal auxiliary circuit in the data structure of the second service provider's equipment to the normal working state, and issue the hardware forwarding entry, and start forwarding the service message; If the pseudowire is in an abnormal working state, set the state of the first sub-attachment circuit in the data structure of the second service provider equipment to be in a normal working state. 6. The method according to claim 4, wherein said step D further comprises: When the state of the second sub-auxiliary circuit is in the abnormal working state, set the state of the first terminal auxiliary circuit in the data structure of the second service provider equipment to the normal working state. 7. The method according to claim 2, characterized in that when the state of the last sub-attached circuit at the first end of the pseudowire changes from a normal working state to an abnormal working state, the first service provider device at the end sends a notification An abnormal message; the abnormal notification message carries the identifier of the sub-attachment circuit. 8. The method according to claim 7, wherein said step C further comprises the steps of: When the second service provider device at the second end of the pseudowire receives the abnormal notification message, it searches for a second sub-attachment circuit having the same first sub-attachment circuit identification field according to the adjunct circuit identifier. 9. The method according to claim 8, wherein the step D specifically comprises: When the state of the second sub-accessory circuit is a normal working state, it is judged whether the state of the pseudo wire is normal; When the pseudowire is in the normal working state, the state of the first sub-attached circuit in the data structure of the second service provider equipment is set to the abnormal working state and the hardware forwarding entry is deleted; Otherwise, only the state of the first sub-accessory circuit in the data structure of the second service provider equipment is set as an abnormal working state. 10. The method according to claim 2, characterized in that the pseudowire encapsulation message format in which multiple service flows share one simulated circuit is adjusted, and the virtual path identifier/virtual channel is replaced by the forwarding index field corresponding to the attached circuit identifier Identifier field, the index identifies a permanent virtual connection. 11. The method according to any one of claims 1 to 10, characterized in that the method further comprises: Determine whether the inner label of the pseudowire has been assigned; If the labels of the pseudowires at both ends of the service provider equipment have been allocated, the state of the pseudowire is the normal working state; otherwise, The state of the pseudowire is the abnormal working state.

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