Heavy-route is a set of mechanism for link protection and Node Protection in MPLS fast, and its basic principle is to protect one or more LSP with a LSP who sets up in advance.In the time of protected LSP link or node failure; find the LSR(Label Switching Router of fault; LSR) utilize the LSP setting up in advance to forward the message on protected LSP; flow continues to pass through after can walking around the link of fault or node like this so that transfer of data is unlikely to interrupt.
In prior art, protected main LSP is specified by manual configuration conventionally, and backup LSP can manual configuration, also can be by automatically setting up.For example, can configure IGP(Interior Gateway Protocol, Interior Gateway Protocol) agreement calculates backup down hop automatically, and also can configure IGP agreement and specify backup down hop by routing policy.Then detect to occur the in the situation that protection being switched whether can form loop by sending message.Form loop if testing result is message repeating, such networking can not form FRR, and main LSP cannot utilize LDP FRR technology to obtain protection; If by detecting, main LSP and backup LSP are formed to FRR.
Some specific network configurations or some specific network configuration can cause forming loop in the time that generation protection is switched, and one of them example refers to Fig. 1.Network shown in Fig. 1 comprises LSR10, LSR20 and the LSR30 that annular connects, the wherein Cost(link overhead between LSR10 and LSR20) value Cost_10-20 is 1, Cost value Cost_10-30 between LSR10 and LSR30 is 1, and Cost value Cost_20-30 between LSR20 and LSR30 need to be set to 3 due to actual networking.
In the time of configuration, LSR10 forms main LSP LSR10 → LSR20 to LSR20, and the forward-path of backup LSP is LSR10 → LSR30 → LSR20, after the LSP between LSR10 and LSR20 breaks down, will utilize backup path to forward.And between LSR30 and LSR20, because Cost_20-30 is greater than (Cost_10-20+Cost_10-30), LSR30 is LSR30 → LSR10 → LSR20 to the main LSP of LSR20, backup path is LSR30 → LSR20.
Before the main LSP of above-mentioned configuration and backup LSP are formed to FRR, need to detect the loop that whether can cause occurring on LSP message repeating in the situation that generation protection is switched.While breaking down in path between the above-mentioned LSR10 of being configured in and LSR20, can there is following situation: because LSR10 is to the main path fault of LSR20, can be switched to backup path LSR10 → LSR30 → LSR20, now LSR30 becomes the downstream LSR of LSR10, can be forwarded to LSR30 by LSR10 by the message from LSR10 to LSR20; And sent fault because LSR30 does not also perceive LSR10 → LSR20 link, and the main path of LSR30 arrival LSR20 is still LSR30 → LSR10 → LSR20 like this, to arriving the message of LSR20 on LSR30, LSR10 is downstream LSR; Like this, at LSR10 to forming loop between LSR30.
Visible, above-mentioned configuration can not be switched the loop detection in situation by protection, and the networking of Fig. 1 cannot form LDP FRR, cannot utilize FRR to carry out error protection.
The MPLS network FRR implementation method that the present embodiment proposes on a kind of LSR of being applied in solves the problems referred to above, and its flow process as shown in Figure 2.
At step S210, take a certain LSP as basis, generate at least two replaceable paths.
This step can adopt mode of the prior art to realize.For example, take certain LSP as main LSP, manually arrange after backup LSP, can and back up LSP as two replaceable paths using this main LSP.For another example, be that a certain LSP finds after other one or more other LSP that can arrive same LSR automatically in existing agreement, one or more other LSP that automatically find and this LSP are formed to the replaceable path of two or more pieces.The present embodiment is not restricted the mode of finding and generate replaceable path.
At least two replaceable paths that generate can be configured to, with active/standby mode operation, also can be configured to move with equivalents.
Under active/standby mode, common protected LSP is main LSP, and manually appointment or the automatic LSP finding are backup LSP, and in the time that main LSP state is normal, message forwards by main LSP in the prior art, and after main LSP breaks down, just LSP is backed up in use.
Under equivalents, all replaceable paths are equative route, there is no main and standby relation, in prior art, message forwards by one in the normal LSP of state, when available path is during more than 1, adopt predetermined algorithm (as hash algorithm) to decide by which bar by LSR and forward, any paths all may be used.
At step S220, to the message of the outgoing interface from a replaceable path, forward from the outgoing interface in other replaceable paths.
When LSR receives from the outgoing interface in a replaceable path the message that need to forward along this LSP, if having other replaceable path at least in normal condition, forward from the outgoing interface in normal other the replaceable paths of state; If the equal abnormal state of the outgoing interface in every other replaceable path, is now in fact equivalent to not exist replaceable path, abandon this message, no longer forward.In the present embodiment, replaceable path outgoing interface abnormal state comprises all situations that cannot normally E-Packet by this outgoing interface, and the link occurs fault that for example this interface itself breaks down, this interface connects, the downstream LSR that this interface connects break down etc.
Under active/standby mode, to carrying out the message of autonomous LSP outgoing interface, forward from the outgoing interface of backup LSP; If the outgoing interface abnormal state of backup LSP, abandons this message.To the message from backup LSP outgoing interface, forward from the outgoing interface of main LSP; If the outgoing interface abnormal state of main LSP, abandons this message.Visible, even main LSP can normally work in the present embodiment, also can adopt backup LSP to carry out message repeating.
Under equivalents, to the message of the outgoing interface from an equative route, from other equative routes, the outgoing interface of a certain forwards; In the time of the outgoing interface abnormal state of every other equative route, abandon this message and no longer forward.Exceed 1 other equative route state when normal when having, can adopt wherein any one to forward, also can determine therein a forward-path with certain algorithm (as hash algorithm), the present embodiment is not restricted this.
In step S220, the forwarding of the upper message of LSR is limited.One skilled in the art will appreciate that LSP is a unidirectional path from entrance LSR to egress LSR in MPLS network, that is to say, active and standby LSR and each LSR of equal value carry out message repeating towards same direction.Therefore,, under most of situation, the reason that forms loop is that of upstream and downstream sends the message of receiving from LSP outgoing interface again to multiple LSR from same outgoing interface.Therefore, in the present embodiment, restriction adopts this pass-through mode, thereby greatly reduces the possibility that forms loop, makes more networking modes to use LDP FRR technology to obtain protection by loop detection.
Switching by protection after the loop detection in situation, forming FRR based on the replaceable path of above-mentioned two or more pieces, thereby can utilize the mechanism of LDP FRR in the time that fault occurs, to carry out the quick switching of replaceable link, reducing flow interrupt.
Still take the MPLS network shown in Fig. 1 as example, after application the present embodiment, in the time carrying out loop detection, under the situation breaking down in the path between LSR10 and LSR20, can there is following situation: because LSR10 is to the main path fault of LSR20, can be switched to backup path LSR10 → LSR30 → LSR20, now LSR30 becomes the downstream LSR of LSR10, can be forwarded to LSR30 by LSR10 by the message from LSR10 to LSR20; And on LSR30, the link that LSR30 does not temporarily also perceive LSR10 → LSR20 has sent fault, its main path that arrives LSR20 is still LSR30 → LSR10 → LSR20, to receive from the outgoing interface of its main path from the message of LSR10, should forward from the outgoing interface of backup path LSR30 → LSR20, therefore message is forwarded to LSR20.Visible, the method for application the present embodiment can avoid forming loop, can meet the requirement of FRR agreement.
In the network shown in fig. 1, if Cost_20-30=2, between LSR30 and LSR20, because Cost_20-30 equals (Cost_10-20+Cost_10-30), LSR30 is to two LSP:LSR30 → LSR10 → LSR20 of LSR20, form equative route with LSR30 → LSR20.LSR10 is LSR10 → LSR20 to the main LSP of LSR20, and backup LSP is LSR10 → LSR30 → LSR20.In the time breaking down in the path between LSR10 and LSR20, LSR10 will forward by backup path LSR10 → LSR30 → LSR20 to the message between LSR20, can be forwarded to LSR30 by LSR10 by the message from LSR10 to LSR20; To LSR30, be to receive from the outgoing interface of path LSR30 → LSR10 → LSR20 from the message of LSR10, therefore should forward from the outgoing interface of another equative route LSR30 → LSR20, thereby can not form loop equally.
Corresponding with above-mentioned flow process realization, the present embodiment provides a kind of FRR implement device of MPLS network, operates in LSR upper, and this device can be realized by software, also can realize by the mode of hardware or software and hardware combining.Be embodied as example with software, as the device on a logical meaning, the present embodiment be CPU by LSR by non-volatile memories wherein corresponding computer program instructions read operation in internal memory and form.Say from hardware view, except the CPU shown in Fig. 3, internal memory and nonvolatile memory, LSR also comprises other hardware conventionally, as being responsible for forwarding chip of processing message processing etc.; May be also distributed equipment from this equipment of hardware configuration, may comprise that multiple interface cards are to carry out the expansion of message processing at hardware view.
Figure 4 shows that the FRR implement device of a kind of MPLS network that the present embodiment provides, be applied on LSR, comprise replaceable path generation unit and message repeating unit, wherein: replaceable path generation unit, for take a certain label switching path LSP as basis, generates at least two replaceable paths; Message repeating unit, for the message to the outgoing interface from a replaceable path, forwards from the outgoing interface in other replaceable paths.
In the optional execution mode of one, described at least two replaceable paths comprise main LSP and backup LSP; Described message repeating unit specifically for: to carrying out the message of autonomous LSP outgoing interface, forward from the outgoing interface of backup LSP; To the message from backup LSP outgoing interface, forward from the outgoing interface of main LSP.
In the optional execution mode of another kind, described at least two replaceable paths comprise at least two equative routes; Described retransmission unit specifically for: to the message of the outgoing interface from an equative route, forward from the outgoing interface of other equative routes.
Described device can also comprise packet loss unit, if for when the outgoing interface abnormal state in every other replaceable path, abandon described message.
Described device can also comprise: FRR forming unit, for by after loop detection, forms FRR with described at least two replaceable paths.
From the execution mode of above the whole bag of tricks and device, can find out; the present invention has adopted new message repeating mode on the LSR with at least two replaceable paths; restriction sends the message receiving from an interface from same interface again; make more networking structure can both avoid forming loop in the time of failover; thereby expanded the range of application of LDP FRR technology, more networking is utilized LDP FRR technology to realize error protection.
The foregoing is only preferred embodiment of the present invention, in order to limit the present invention, within the spirit and principles in the present invention not all, any modification of making, be equal to replacement, improvement etc., within all should being included in the scope of protection of the invention.