Method and system for providing failure protection in a ring network that utilizes label switching
View Patent ↗A working label switched path (LSP) between neighbor label switched routers (LSRs) in a ring network that utilizes label switching is protected by an LSP that connects the neighbor LSRs of the working LSP in an opposite direction to the working LSP. If the working LSP fails, then packets are switched to the protection LSP. Switched packets traverse the protection LSP until they reach the neighbor LSR that they would have reached had the packets traversed the working LSP. Time-to-live (TTL) values of packets that traverse the protection LSP are adjusted to account for the number of hops on the protection LSP so that the TTL values of the packets are the same after traversing the protection LSP as they would have been had they traversed the working LSP. After traversing the protection LSP packets can be switched back to the working LSP or switched to a next hop LSP.
1. A method for protecting a label switched path (LSP) between two label switch routers (LSRs) in a ring network that utilizes multiprotocol label switching (MPLS) to communicate packets of information, wherein each LSR in said ring network is connected to a right side neighbor LSR and a left side neighbor LSR by respective links, said method comprising:
identifying a working LSP between first and second neighbor LSRs in said ring network, said working LSP having a first direction around said ring network;
establishing a protection LSP between said first and second neighbor LSRs for communicating packets between said first and second neighbor LSRs in the event of a failure of the link that is utilized by said working LSP, said protection LSP utilizing said ring network and having an opposite direction to said first direction;
switching packets from said working LSP to said protection LSP in response to a failure of said link that is utilized by said working LSP, wherein switching packets from said working LSP to said protection LSP includes adjusting time-to-live (TTL) values of said packets to account for the number of LSRs that are along said protection LSP;
switching packets back to said working LSP from said protection LSP after said packets have traversed said protection LSP; and
using TTL values from packets that have traversed said protection LSP to generate TTL values for said packets that are switched back to said working LSP from said protection LSP.
2. The method of claim 1 wherein switching packets from said working LSP to said protection LSP includes switching the label of a packet from a working label to a protection label.
3. The method of claim 1 wherein adjusting said TTL values includes adding N to said TTL values, where N is a function of the number of LSRs along said protection LSP.
4. The method of claim 1 further including establishing at least one protection LSP for each link between neighbor LSRs on said ring network.
5. A system for protecting a label switched path (LSP) between two label switch routers (LSRs) in a ring network that utilizes multiprotocol label switching (MPLS) to communicate packets of information between LSRs in said ring network, wherein each LSR in said ring network is connected to a right side neighbor LSR and a left side neighbor LSR by respective links, each LSR in said ring network comprising:
a label switching module, associated with an LSR, for identifying a working LSP between said LSR and a neighbor LSR, said working LSP having a first direction around said ring network; and
a failure protection module for:
establishing a protection LSP between said LSR and said neighbor LSR that enables packets to be communicated between said LSR and said neighbor LSR in the event of a failure of the link that is utilized by said working LSP, said protection LSP utilizing said ring network and having an opposite direction to said first direction; and
switching packets from said working LSP to said protection LSP in response to a failure of said link that is utilized by said working LSP, wherein switching packets from said working LSP to said protection LSP includes adjusting TTL values of said packets to account for the number of LSRs that are along said protection LSP; and
switching packets back to a working LSP from a protection LSP after said packets have traversed said protection LSP; and
using TTL values from packets that have traversed said protection LSP to generate TTL values for said packets that are switched back to said working LSP from said protection LSP.
6. The system of claim 5 wherein switching packets from said working LSP to said protection LSP includes switching the label of a packet from a working label to a protection label.
7. The system of claim 5 wherein adjusting said TTL values includes adding N to said TTL values, where N is a function of the number of LSRs along said protection LSP.
8. The system of claim 5 wherein said failure protection module includes logic for establishing unique protection LSPs for working LSPs that utilize the link between said LSR and said neighbor LSR.
9. A method for protecting a label switched path (LSP) between two label switch routers (LSRs) in a ring network that utilizes multiprotocol label switching to communicate packets of information, wherein each LSR in said ring network is connected to a right side neighbor LSR and a left side neighbor LSR by respective links, said method comprising:
identifying a working LSP between first and second neighbor LSRs in said ring network, said working LSP having a first direction around said ring network;
establishing a protection LSP between said first and second neighbor LSRs for communicating packets between said first and second neighbor LSRs in the event of a failure of the link that is utilized by said working LSP, said protection LSP utilizing LSRs on said ring network and having an opposite direction to said first direction;
switching packets from said working LSP to said protection LSP in response to a failure of said link that is utilized by said working LSP;
adjusting TTL values of said switched packets by a value that is a function of the number of LSRs along said protection LSP;
switching packets back to said working LSP from said protection LSP after said packets have traversed said protection LSP; and
using TTL values from packets that have traversed said protection LSP to generate TTL values for said packets that are switched back to said working LSP from said protection LSP.
10. The method of claim 9 wherein adjusting said TTL values includes adding N to said TTL values, where N is a function of the number of LSRs along said protection LSP.
11. The method of claim 9 further including establishing at least one protection LSP for each link between neighbor LSRs on said ring network.