EP1260064A2 - Circuit arrangement for providing a back-up circuit for transmission devices in ring architectures that route mpls packets - Google Patents

Abstract

In prior art, the provision of back-up circuits for ATM cells in ring-type structures is efficiently controlled using linear structures. According to the invention, this function is extended to ring-type MPLS network architectures as follows: linear MPLS structures are formed into a ring-type MPLS structure and two unidirectional MPLS connections which respectively connect the same switching devices and run in opposite directions are logically associated to one another, whereby the operating link and the back-up link are routed via different physical paths.

Description

description

_S chaltungsanordnung to replace switching Übertragungsem- πchtungen m MPLS packets drove annular architectures.

The invention relates to a circuit arrangement according to the preamble of claim 1.

A circuit arrangement for the equivalent switching of transmission devices in ring architectures is already known from German patent application DE 197 039 93.6.

This known circuit arrangement relates to transmission devices via which information is routed according to an asynchronous transfer mode (ATM). In this case, a transmission device for bidirectional transmission of digital signals is provided, in which two switching devices functioning as end points are connected to one another via a plurality of operating lines and a replacement line. The two end stations each contain monitoring devices for detecting transmission faults. A switching device controllable by a monitoring device connects a receiving device in a first switching state to the operating path and in a second switching state to the replacement path.

A disadvantage of this known circuit arrangement is that it relates exclusively to ATM transmission devices. On the Internet, information about a plurality of network nodes, which can be designed as routers, is supplied to the receiving subscriber. MPLS networks can be arranged between the routers. MPLS networks are not addressed at all in the known circuit arrangement.

The invention has for its object to develop a circuit arrangement of the type mentioned in such a way that information transmitted according to an Internet protocol can be transmitted with great certainty over a plurality of network ^nodes .

The invention is achieved on the basis of the features indicated in the preamble of patent claim 1 by its characterizing features ^¬ designating characteristics.

An advantage of the invention is especially that a multi ^¬ MPLS switches li--linear Ubertragungsabschnitten formed are joined together to form a ring system of paying out. A transmission section is formed by an operating route and / or a replacement route. Furthermore, two opposing unidirectional MPLS connections are logically associated with one another, each of which connects the same MPLS switching devices, with the operating link and replacement link being routed via different physical paths. The MPLS switching devices are designed as label switched routers. This has the advantage that MPLS connections can be maintained in an efficient manner in the event of a malfunction of the operating link in ring systems developed in this way.

Advantageous developments of the invention are specified in the subclaims.

The invention is explained in more detail below on the basis of an exemplary embodiment.

Show it:

1 shows an MPLS network integrated into the Internet,

FIG. 2 shows a configuration for the transmission of MPLS packets in a linear 1 + 1 structure,

FIG. 3 shows a configuration for the transmission of MPLS packets in a linear 1: 1 structure, FIG. 4 shows the circuit arrangement according to the invention,

In FIG. 1 is shown an example of how information to a subscriber TLN 2 are leads to ^{¬ ¬} Found _ü from going from a subscriber TLN 1. The sending subscriber TLN1 is connected to the Internet network IP, through which the information is routed according to an Internet protocol, such as the IP protocol. This protocol is not an association-oriented protocol. The Internet network IP has a plurality of routers R, which can be meshed with one another. The receiving subscriber TLN2 is connected to a further Internet network IP. An MPLS network (Multiprotocol Packet Label Switchmg) is inserted between the two Internet networks IP, through which information in the form of MPLS packets is switched through in a connection-oriented manner. This network has a plurality of routers meshed with one another. In an MPLS network, these can be so-called label switched routers (LSR). One of the routers is referred to as the sending device W and another as the receiving device E.

MPLS packages each have a header and an information point. The head part is used to record connection information, while the information part is used to record useful information. IP packets are used as useful information. The connection information contained in the header is designed as an MPLS connection number. However, this is only valid in the MPLS network. If an IP packet from the Internet network IP thus penetrates the MPLS network, the header that is valid in the MPLS network is appended to it. Then all connection information is contained that specify the path of the MPLS packet in the MPLS network. If the MPLS packet leaves the MPLS network, the header is removed again and the IP packet is routed on in the subsequent Internet network IP in accordance with the IP protocol. In FIG. 2, two nodes are by way of example of an MPLS network m a linear configuration shown, each of which is as _V detecting means W, E formed. In present ^¬ the _A usfuhrungsbeispiel is assumed that it is in these switches to MPLS cross-connect switches. However, the use of switching ^devices formed in this way does not imply any restriction of the invention; other switching devices such as ATM switching devices can also be used. In FIG. 2 now are MPLS packets (Multi Protocol La ^¬ bel Switched packets) are transmitted from the designed as label switched routers W switching means to the designed as a Label Switched Router E switch back.

Fig. 2 shows a linear 1 + 1 structure. A bidirectional transmission case is also shown here. The transmission of MPLS packets in the MPLS network is defined unidirectionally. Accordingly, in the bidirectional transmission case for the forward and backward transmission of a connection WT associated MPLS packets between the label switched router W and the label switched router E, a total of 2 "connections (one for the execution and one for the reverse direction) must be established. A “connection * in the MPLS network is called a label switched path (LSP).

The label switched routers W, E are connected to one another via an operating link WE (WORKING ENTITY) and a replacement link PE (PROTECTION ENTITY). The operating route WE can optionally also be formed from a plurality of operating routes. Switching devices S (BRIDGE) are also shown, via which the incoming MPLS packets are received and the operating lines WE are transmitted to the label switched router E hm. Fig. 2 can also be found selection devices SN, the task of which is that of the

Operating line WE to transmit MPLS packets transmitted to the output of the label switched router E. According to the present For example, the selection devices SN are designed as a switching matrix. The switching network SN is both assigns the label _S witched router W as being in the label switched router E ^¬.

_W eiterhin are shown in two label switched routers W, E surveil ^¬ monitoring devices UE _o UEi (PROTECTION DOMAIN SINK, PROTECTION DOMAIN SOURCE) that monitor packages the state or the quality of the data transmitted via the service links WE MPLS. For example, the MPLS packets of the connection with the number 1 WTi, before they are transmitted over the operating route WE to the label switched router E hm, are loaded with control information by the monitoring device UEi of the label switched router W which the monitoring device UEi of the receiving one Label Switched Router E removes and checks. This control information can then be used to determine whether the MPLS packet has been transmitted correctly or not. In particular, a total failure (SIGNAL FAIL FOR WORKING ENTITY) of the operating route WE can be determined. However, deteriorations in the transmission quality (SIGNAL DEGRADE) can also be determined using known methods.

The monitoring devices UEi close the operating route WE on both sides. Further monitoring devices UEo are arranged on both ends of the replacement route PE. In the event of a fault, this should serve as a transmission link for the decommissioned operating link WE. Furthermore, substitute switching protocols ES are transmitted, so that the integrity of the substitute route has top priority.

Central control devices ZST are also arranged in each of the label switched routers W, E. These each contain local and global priority tables, in which the state and priority of the local label switched router W (local priority table) as well as the state and priority of the local and be performed of the remaining label switched router E (global Priori ^¬ tätstabelle). Activities by the introduction of Priori ^¬ is achieved that several upon the concurrence ^¬ rer protection switching requests is determined which operating range in case of the presence of several operating stretch is spare switch. The equivalent ^switching requests are also prioritized in the priority tables. For example, there is a high priority requirement from a user. Since this equivalent switching request is assigned a high priority, it is therefore preferably controlled.

An equivalent switching request controlled by one of the operating lines and to which a lower priority is assigned is therefore rejected.

The central control devices ZST of the label switched router W, E exchange information in an equivalent switching protocol ES. This protocol is transmitted over the substitute route PE and taken from the assigned monitoring device ÜE _{0 of} the respective label switched router that is received, and fed to the relevant central control device ZST. Furthermore, care is taken in the central control device ZST that the switching devices S are actuated in a corresponding manner in the event of a fault.

In the protocol ES Information K _are stored K _2nd The first is information relating to the generated equivalent switching request, while the latter is information relating to the current states of the switching devices. The protocol ES is exchanged between the two label switched routers W, E when an equivalent switching request is generated. A special embodiment of the invention provides for the protocol ES to be transmitted cyclically between the two label switched routers W, E.

3 shows a further linear structure with which MPLS packets can be switched in replacement. This is a 1: 1 structure. The difference to that in Fig. 2 shown 1 + 1 structure is that the bridge devices _{S shown} there are designed as switching devices _So , _S i. The selection device SN is also here designed as a coupling box, as shown in Fig. 2. The UE he _b the protection link PE forwarded MPLS packets are supplied to the switching network ^¬ sem. The logical MPLS connection number is now taken from the packet header, evaluated and switched through the switching matrix. The activation of switching devices is therefore not necessary in the receiving switch. . In the two label Swit ^¬ ched routers W, E of Figure 3 are as - did not show up ^¬ - include central control means with local and global priority tables.

The replacement route PE can remain unused during this time. If necessary, special data (EXTRA TRAFFIC) can also be supplied to the label switched routers E during this time.

The protocol ES is designed here in a different way than in the first case. So, in addition to the information already mentioned in the first case, further information is stored here with respect to the generated equivalent switching request. This is information relating to the current states of the switching devices S ₀ , S _ι . In the event of a fault, the switching devices S ₀ , Si must be controlled in a corresponding manner. The protocol is exchanged between the two label switched routers W, E when the equivalent switching request is generated. A special embodiment of the invention provides for the protocol ES to be transmitted cyclically between the two label switched routers W, E.

The circuit arrangement according to the invention is shown in FIG. 4 (dedicated protection). Dedicated protection means that the bandwidth per MPLS switched path is fixed both on the operating route WE and on the replacement route PE. is served. The label switched routers are switched so that there is a closed ring. According to the present exemplary embodiment, this ring is to be made up of linear connecting sections, as shown in FIG. 2 or 3. According to present, in Fig. 4 ^¬ be written exemplary embodiment of the ring is from the m Fig. 2 indicated linear 1 + 1 structure can be formed without this being a preference for this structure is to be indicated.

4 shows label switched routers N _A , N _B , N _c and N _D on ^¬ . Two label switched routers each terminate transmission sections. Using the example of the label switched routers N _A and N _D , these are the connection sections WE _A -D_ SO- and WE _D _ _A. Using the example of the label switched routers N _A and N _B or N _B , N _c or N _c , N _D , these are the connection sections PEA-D and PE _D _ _A.

4, each of these label switched routers has a bridge device S and a selection device SN. The label switched routers should be switched in such a way that the respectively active operating lines WE _A - _D _ and WE _D _ _A are arranged between the label switched routers N _A and N _D. The MPLS packets arriving via the connection WT _A -E_ and WT _D - _A are then routed via these operating routes. The spare routes are, however, directed by the label switched router N _A via further label switched routers N _B, N _c to the label switched router N _D. There the MPLS packets leave the ring for further equipment.

The ring FIG. 4 formed by the label switched router is also bidirectional. The reverse direction of the connection WT _A - _D is formed by the connection WT _D _ _A. For better understanding, it should be noted that both connections are treated separately, even though it is a bidirectional connection. It is essential that exactly one replacement route is assigned to the respective operating route is. _S omit the operating link WE _A _ _D _the standby link PE _A _ _D and functions as a reverse direction operation range _D WE -A is the standby link PE _D - _A assigned. Further, as Ausgestal ^¬ processing disclosed in FIG. 4 configuration, a transmission case unidi- rektionaler possible.

Monitoring means being arranged ^¬ - Furthermore, in each Label Switched Router - 4 not been showed in Fig.. These complete the operating lines WE _A _ _D _ and WE _D - _A as well as the replacement lines PE _A _ _D and PE _D - _A. Furthermore, who the all run on the same physical path MPLS connections * (Label Switched Path) summarized ^¬ logical to a group that are being created bonds 2 Ersatzschaltever- for this group. The first of these substitute switch connections is routed via the operating line WE (MPLS substitute switch LSP; LSP = Label Switched Path), with which it is routed via the same physical path between the label switched routers W and E as all the associated individual connections. The second of these equivalent switching connections is set up via the equivalent route PE.

In the group protection switching process only these two protection switching connections to failures and faults in the monitoring devices UE are _now: UE ₀ monitored. The individual connections are no longer monitored. In the case of an equivalent switching request, the priority-controlled equivalent switching decision is made in the local priority logic as before. In the case of a replacement, however, all the individual connections belonging to a group are switched over together by the switching device SN. In this case, only a single equivalent switching protocol has to be processed via the alternative route PE.

The advantage of this is that a multiplicity of individual connections can be monitored and switched by a single spare switching connection and a single spare switching protocol, in order to be able to adapt to those in practical operation on to be able to react appropriately to the most common errors. Furthermore, a protection switching protocol is only he entered local priority table in _d. This has the _V orteil that the protection switching protocol in case of failure of a working link is to transmit only once. This assumes _d Avon that a protection switching protocol would otherwise be transmitted per MPLS path number. However, this would result due to the large number of MPLS connections to dy namic ^¬ load of the ring. However, since a plurality of connections to the same MPLS connection number Densel use ^¬ ben transfer portion and potential interference usually affects the entire transmission section, a logical bundling of the MPLS connection number is advantageous to a logical group number.

In the following will be assumed that the compound WT _A - _D requires that the associated MPLS packets over the label switched router N _A ring are supplied via the label switched router N _D leave same. In this case, the compound _A WT thus be - _D supplied to the associated MPLS packets of the label switched router arranged in N _A S bridge means. Since this is permanently set, the MPLS packets are forwarded to the Label Switched Router [both via the operating link WE _A _ _n and via the replacement link PE _A _ _D and leave the ring there.

In the event of a fault, ie if there is no operational malfunction on the active operating path, the MPLS packets are routed directly from the label switched router N _A to the label switched router N _D. However, if an operational fault occurs here, this is determined by the monitoring device arranged in the receiving label switched router. In the present case, this should be the label switched router N _D. Thereupon the equivalent switching protocol is immediately supplied by the latter via the assigned alternative route PE _A - _D to the sending label switched router, that is to say the label switched router N _A. At the same time, the selection device SN controlled in the operating state that accepts MPLS packets over the replacement route PE _A - _D.

The monitoring devices also check the operating condition on the replacement routes. For example, MPLS packets transmitted via the operating link WE _A _ _D and is now on the receiving label switched router, so the label switched router N _π a Storungsfall on the assigned He set distance ^¬ PE _A - determined _D, then it will be in Ersatzschalte- Protocol filed information communicated this to the transmitting label switched routers N _A. This prevents that in the event of an additional fault on the active operating link WE _A - _D, a switchover to a faulty replacement link PE _A - _D takes place.

According to the invention, the equivalent switching protocol ES is only exchanged when faults occur, but a cyclical exchange can also be controlled. Likewise, the replacement switching protocol can be changed individually for each MPLS connection number. However, it must be taken into account that in these cases there is a dynamic additional load on the ring. However, it is advantageous here that connection-specific interference with regard to the MPLS connection number can be dealt with using such a procedure. With the preferred embodiment of the group replacement circuit, only the most frequently occurring fault on the route can be dealt with.

In conclusion, it should be noted that the ring in the present exemplary embodiment is made up of linear 1 + 1 structures. However, the use of a 1: 1 structure according to FIG. 3 brings further advantages. Although the equivalent switching protocol is more complex here, special data can be transmitted over the alternative route during the trouble-free time on the operating route. General tax data can be used as special data. inventions dung in accordance with the special data as special Ver ^¬ traffic data be made.

_{T he S} can onderdaten via the protection link also niederpri- listener traffic to be transmitted, which will only bear the net about ^¬ when resources are plentiful. The low-priority traffic is then in this case by replacing ^¬ turn the high-priority traffic automatically displaced. In this case, the replacement of the special data in the case of a replacement does not take place by switching the switching device S in FIG. 2, but by prioritizing the high-priority traffic over the low-priority special data in each transmission device.

The operating and replacement lines WE and PE must be set up before commissioning. For this purpose, connections between the label switched routers W and E and, if appropriate, at intermediate transmission devices must be set up (configured).

These connections are usually set up using TMN (Telecommunications Network Management), but can also be done using an MPLS signaling protocol. For this purpose, the route of the operating or replacement route is determined by signaling. In addition, bandwidth is reserved in the transmission devices via the signaling protocol, so that the transmission of the information via the operating or replacement route is ensured.

Claims

claims 1. _S chaltungsanordnung for protection switching of Ubertragungs- e πchtungen, with at least two switching devices (N _A, N _D), each ^¬ weils one from operating links (WE _{A, D,} WE _{D. A)} and / or He set stretch ^¬ (PE _A - _D , PE _D _ _A ) complete the formed transmission section, and between which information about this transmission section is exchanged, whereby in the event of a fault on the transmission section in question, the information transmitted so far about this, depending on the criteria of criteria and logical connection information, possibly to the replacement route are diverted, characterized in that the information is inserted in MPLS packets, that two opposing unidirectional MPLS connections are logically associated with one another, the two opposing MPLS connections each connecting the same switching devices in such a way that several linear transmission sections are combined in such a way that a ring line system is formed, the operating route and replacement route being carried out via different physical paths. 2. Circuit arrangement according to claim 1, characterized in that a unidirectional loop system is formed by using unidirectional switching devices, whereby the logical association of the two opposite, unidirectional MPLS connections is omitted. 3. Circuit arrangement according to claim 1, 2, characterized in that the operating route (WE _A - _D , E _{D. A} ) is assigned a replacement route (PE _A _ _D , PE _D _ _A ), and both routes are each assigned a priority , 4. _S chaltungsanordnung according to claim 1, 2 or 3, characterized in that _d ate in the protection switching case, a protection switching request is generated ^¬ riert which further priorities are assigned. 5. Circuit arrangement according to claim 1, 2 or 4, characterized in that the logical connection information is the MPLS connection ^¬ number (label value). 6. Circuit arrangement according to one of the preceding claims, characterized in that the logical connection information of an MPLS connection is the number of an MPLS connection group which is formed from a plurality of MPLS connections. 7. Circuit arrangement according to one of the preceding claims, characterized in that local and global priority tables are provided in which the order of priority is fixed. 8. Circuit arrangement according to one of the preceding claims, characterized in that when an equivalent switching request arrives in the receiving switching device, an equivalent switching protocol is generated, which is supplied only once via the replacement link (PE) to the transmitting switching device. 9. Circuit arrangement according to one of the preceding claims, characterized in that total incidence and deterioration of an operating route in the monitoring device of the receiving switching device can be determined. 1 ₀ . _S chaltungsanordnung according to any one of the preceding claims, characterized in that the switching devices as MPLS cross-connect _S chalteinrichtungen are formed. 11. _S chaltungsanordnung according to any one of the preceding claims, characterized in that the equivalent circuit is optionally carried out by driving a contained in the transmitting switching device switching means (S _0, Si) as well as using a arranged in the em ^¬ pfangenden switch selection device (SN) , 12.Circuit arrangement according to one of the preceding claims, characterized in that special data are transmitted over the replacement route (PE) in periods of no malfunction. 13. Circuit arrangement according to one of the preceding claims, characterized in that the special data are designed as low-priority traffic, which is automatically displaced in the event of an equivalent switching of the high-priority traffic. 14. Circuit arrangement according to one of the preceding claims, characterized in that the selection device (SN) is designed as a switching matrix and / or as a simple switching element. 15. Circuit arrangement according to one of the preceding claims, characterized in that the switching device (S) arranged in the transmitting switching device is fixedly adjustable. 16. _S chaltungsanordnung according to any one of the preceding claims, characterized in that _{ß d} as protection switching protocol is exchanged cyclically between the lungsemrichtung send ^¬ the switching device and the receiving intermediary. 17. Circuit arrangement according to one of the preceding claims, characterized in that a group equivalent circuit is provided by logically combining all MPLS connections conducted via the same physical path into a group, and creating at least two equivalent circuit connections for the group formed in this way, one each this equivalent switching connections over an operational route (WE) and another of these equivalent switching connections over the alternative route (PE) is set up. 18. Circuit arrangement according to one of the preceding claims, characterized in that in the case of the provision of a group equivalent circuit, only the at least two equivalent circuit connections are monitored by the monitoring devices (ÜE ₀ ... UE _n ). 19. Circuit arrangement according to one of the preceding claims, characterized in that the establishment of the connections carried over the at least one operating path (WE) and the connections carried over the replacement path (PE) is carried out by means of an MPLS signaling protocol, which also includes bandwidth Reserved in the transmission directions and determines the route of the operating route (s) (WE) and the replacement route (PE).