Distributed connectivity verification protocol redundancy

Abstract

In one embodiment, a connectivity verification protocol (CVP) session for a particular virtual interface (VI) may operate on a particular group of two or more line cards (LCs) on a network device. The group of LCs may then transmit CVP session packets, at a reduced rate that is sufficient to maintain the CVP session based on a negotiated CVP full rate, onto the particular VI through ingress path processing on the network device. Ingress path processing, in particular, takes transmitted CVP session packets and egresses them onto an appropriate LC of the network device currently responsible for the VI egress. Also, in response to receiving CVP session packets for the VI on an LC of the network device currently responsible for the VI ingress, the receiving LC may forward the received CVP session packets to the particular corresponding group of LCs, which may then process the received CVP session packets.

1 . A method, comprising:
 maintaining state for a connectivity verification protocol session corresponding to a virtual interface via a group of line cards comprising a primary line card and a backup line card;   transmitting, from the primary line card and the backup line card, connectivity verification protocol session packets to the virtual interface, wherein the primary line card actively transmits verification protocol packets at a first reduced rate that is less than a negotiated full rate and the backup line card actively transmits verification protocol packets at a second reduced rate that is less than the negotiated full rate, and wherein a combination of the first rate and the second rate is sufficient to maintain the connectivity verification protocol session at the negotiated full rate;   receiving, by the primary line card and the backup line card, a connectivity verification protocol session packet associated with the connectivity verification protocol session corresponding to the virtual interface; and   processing, via at least one of the primary line card and the backup line card, the connectivity verification protocol session packet received by the primary line card and the backup line card.   
     
     
         2 . The method of  claim 1 , wherein processing the connectivity verification protocol session packet comprises based on the connectivity verification protocol session packet received, determining a state of at least one of a sending device associated with the virtual interface or the connectivity verification protocol session. 
     
     
         3 . The method of  claim 1 , wherein the connectivity verification protocol session comprises bidirectional forwarding and detection protocol session. 
     
     
         4 . The method of  claim 1 , wherein the primary line card establishes the connectivity verification protocol session or tears down the connectivity verification protocol session, and wherein processing the connectivity verification protocol session is performed via the primary line card. 
     
     
         5 . The method of  claim 1 , further comprising:
 in response to a failure associated with one of the primary line card or the backup line card, receiving state of the connectivity verification protocol session via a new line card assigned to the group of line cards.   
     
     
         6 . The method of  claim 1 , further comprising:
 in response to a failure associated with one of the primary line card or the backup line card, transmitting connectivity verification protocol session packets via a remaining line card from the group of line cards, wherein the verification protocol session packets are transmitted at the negotiated full rate.   
     
     
         7 . The method of  claim 6 , further comprising:
 transmitting connectivity verification protocol session packets from the remaining line card and a new line card assigned to the group of line cards after the failure, wherein each of the remaining line card and the new line card transmits connectivity verification protocol session packets at a respective rate that is less than the negotiated full rate, and wherein a combination of the respective rate of the remaining line card and the new line card is sufficient to maintain the connectivity verification protocol session at the negotiated full rate.   
     
     
         8 . The method of  claim 1 , wherein the sending device comprises a second group of line cards associated with the virtual interface, and wherein the virtual interface comprises one of a tunnel or a pseudowire. 
     
     
         9 . The method of  claim 1 , wherein the first reduced rate is different than the second reduced rate. 
     
     
         10 . The method of  claim 1 , further comprising:
 in response to a failure associated with the primary line card, obtaining, via the backup line card, a reassignment designating the backup line card as a new primary line card to replace the primary line card associated with the failure.   
     
     
         11 . The method of  claim 1 , wherein the connectivity verification protocol session packet received comprises a group identifier within a discriminator value of the connectivity verification protocol session packet, the group identifier indicating a particular group of line cards associated with the sending device. 
     
     
         12 . A system, comprising:
 a processor; and   a computer-readable storage medium having stored therein instructions which, when executed by the processor, perform operations comprising:
 maintaining state for a connectivity verification protocol session corresponding to a virtual interface via a group of line cards comprising a primary line card and a backup line card; 
 transmitting, from the primary line card and the backup line card, connectivity verification protocol session packets to the virtual interface, wherein the primary line card actively transmits verification protocol packets at a first reduced rate that is less than a negotiated full rate and the backup line card actively transmits verification protocol packets at a second reduced rate that is less than the negotiated full rate, and wherein a combination of the first rate and the second rate is sufficient to maintain the connectivity verification protocol session at the negotiated full rate; 
 receiving, by the primary line card and the backup line card, a connectivity verification protocol session packet associated with the connectivity verification protocol session corresponding to the virtual interface; and 
 processing, via at least one of the primary line card and the backup line card, the connectivity verification protocol session packet received by the primary line card and the backup line card. 
   
     
     
         13 . The system of  claim 12 , wherein processing the connectivity verification protocol session packet comprises based on the connectivity verification protocol session packet received, determining a state of at least one of a sending device associated with the virtual interface or the connectivity verification protocol session. 
     
     
         14 . The system of  claim 12 , the computer-readable storage medium storing additional instructions which, when executed by the processor, perform an operation comprising processing, via the backup line card, at least one of the connectivity verification protocol session or the connectivity verification protocol session packet received as a new primary line card after being assigned as the new primary line card to replace the primary line card associated with the failure. 
     
     
         15 . The system of  claim 12 , wherein the first reduced rate is equivalent to the second reduced rate, and wherein the connectivity verification protocol session packet received comprises a group identifier within a discriminator value of the connectivity verification protocol session packet, the group identifier comprising an identifier corresponding to the group of line cards. 
     
     
         16 . The system of  claim 12 , wherein the sending device comprises a second group of line cards associated with the virtual interface, wherein the virtual interface comprises one of a tunnel or a pseudowire, and wherein the connectivity verification protocol session packets are encapsulated according to a particular type of encapsulation. 
     
     
         17 . A non-transitory computer-readable storage medium having stored therein instructions which, when executed by a processor, perform operations comprising:
 maintaining state for a connectivity verification protocol session corresponding to a virtual interface via a group of line cards comprising a primary line card and a backup line card;   transmitting, from the primary line card and the backup line card, connectivity verification protocol session packets to the virtual interface, wherein the primary line card actively transmits verification protocol packets at a first reduced rate that is less than a negotiated full rate and the backup line card actively transmits verification protocol packets at a second reduced rate that is less than the negotiated full rate, and wherein a combination of the first rate and the second rate is sufficient to maintain the connectivity verification protocol session at the negotiated full rate;   receiving, by the primary line card and the backup line card, a connectivity verification protocol session packet associated with the connectivity verification protocol session corresponding to the virtual interface; and   processing, via at least one of the primary line card and the backup line card, the connectivity verification protocol session packet received by the primary line card and the backup line card.   
     
     
         18 . The non-transitory computer-readable storage medium of  claim 17 , wherein processing the connectivity verification protocol session packet comprises based on the connectivity verification protocol session packet received, determining a state of at least one of a sending device associated with the virtual interface or the connectivity verification protocol session. 
     
     
         19 . The non-transitory computer-readable storage medium of  claim 17 , storing additional instructions which, when executed by the processor, perform an operation comprising changing a role of the backup line card from backup to primary, wherein changing the role is performed by the backup line card after being assigned as a new primary line card to replace the primary line card associated with the failure. 
     
     
         20 . The non-transitory computer-readable storage medium of  claim 17 , storing additional instructions which, when executed by the processor, perform operations comprising:
 synchronizing a first clock of the backup line card with a second clock of the primary line card; and   negotiating a detection multiplier for allowing a number of missed connectivity verification protocol session packets to be missed prior to declaring the connectivity verification protocol session down.