Patent Application
20080031129
The invention will be better understood from the following description of preferred embodiments together with reference to the accompanying drawings, in which:
a illustrates the management of rules
Given the ability of the VMS to ensure that each direction of the connection uses the same path (as per
Other examples of uses for this path association could be where two uni-directional paths with different characteristics are paired (such as different labels and traffic engineering information in the case of MPLS), or where a single path is the hairpin connection for multiple unidirectional paths
The hairpin allows nodes in the network to send messages (such as port-state) back to their ingress point by sending packets back along the hairpin path without the need to hold additional information about the entire path without the need to consult higher level functions outside of the datapath, or to involve the transit end of the path. If the path is already bidirectional, no hairpin is required for pairing.
Using the hairpin to its full potential requires the use of a new subsystem referred to herein as a “packet treatment rule” or “rules” for short. These rules are assigned to an ingress interface and consist of two parts (
(1) ingress matching criteria 407: this is a check to see if the packet in question is to be acted upon or to simply pass though the rule subsystem with no action.
(2) an action mechanism 408 that is called if a packet does meet the criteria of a packet to be acted upon. An example of an action mechanism is where a rule was placed on an ingress interface looking for a prescribed bit-pattern within the packet. When the system receives a packet that matches the prescribed bit-pattern, the action mechanism is run. This action mechanism may be one that directs the system to send this packet back out the interface at which it was received after altering it in some way. All other packets pass through the system unaffected.
Rules can be placed at each node along a path to use the hairpin to loop-back one or more types of packet, or all packets crossing a port. Rules can also be activated by types of packets or other rules, allowing complicated rules that activate other rules upon receiving an activation packet or and deactivate rules on receiving a deactivation packet.
As exemplified in
The creation of path snakes is also easily implementable using hairpins (see
In the case of
The hairpin is always available at each node for each connection. Rules can be enabled (and later disabled) to look for specific types of control messages (e.g., loop-back) and act on them.
Hairpins can also used for other mechanisms described below such as protection switching, network migration and flow control.
One embodiment provides sub-50msec path protection switching for Ethernet point-to-point path failures in order to meet the reliability requirements of the carriers is without using a large amount of control messages. Furthermore, the back-up path is established and triggered based not only on available resources but also on business policies as described above.
The back-up path is calculated using the VMS, and not via typical signaling mechanisms, which configures the switches' 201 control plane with the protected path. The back-up path is set up by the VMS and does not require use of routing protocols such as OSPF. Once the back-up path is set up, the VMS is not involved in the protection switching. The process is illustrated in FIG. EP-1. When a node 201 detects a link failure 501 (via any well-known method, such as loss of signal), it creates a control message 504 and sends the message back along the system using the hairpin 303 (as described above) to indicate to the source endpoint of each connection using the failed link that they need to switch to the back-up path. The switching is then done instantaneously to the back-up path 505. If the uni-directional paths are MPLS-Label switched paths, the hairpin allows the system to send the message back to the path's origination point without the need to consult a higher-level protocol.
The node can use the same mechanisms to notify the sources that the primary path failure has been restored. Depending on the business policies set up by the carrier, the connection can revert to the primary path.
After a connection has been switched to a back-up path, the VMS is notified via messaging that the failure has occurred. The VMS can be configured to make the current path the primary path and to recalculate a new back-up path for the connection after some predetermined amount of time has elapsed and the primary path was not restored (e.g., after 1 minute). The information about the new back-up path is then sent down to the nodes without impact to the current data flow, and the old configuration (failed path) is removed from the configuration. Alternatively, the VMS can also be configured to find a new primary path and send a notification for switch over. The backup protection path remains as configured previously.
If the a User-Network-Interface (UNI) or Network-Network-Interface (NNI) at an end-point of a path fails, the endpoint can also use hairpins to send a control message to the traffic source to stop the traffic flow until the failure is restored or a new path to the destination can be created by the VMS, which is notified of the failure via messaging.
Leveraging the E-line protection scheme, the Switch 201 can create duplicate packet streams using the active and the backup paths. Sequence numbers are used to re-combine the traffic streams and provide a single copy to the server application. If the application does not provide native sequence numbers, they are added by the system.
One implementation of this behavior is shown in
One example of a packet duplication routine is depicted in
A packet recombination routine 611 listens for the sequenced packets and provides a single copy to the server application 601. It removes the sequence numbers if these are not natively provided by the client application 600 data.
One example of a packet recombination routine is shown in
This system does the duplication at the more relevant packet level as opposed to the bit level of other previous implementations (as data systems transport packets not raw bit-streams) and that both streams are received and examined, with a decision to actively discard the duplicate packet after it has been received at the far end. Thus, a switch or link failure does not result in corrupted packets while the system switches to the other stream, because the system simply stops receiving duplicated packets.
Those skilled in the art will recognize that various modifications and changes could be made to the invention without departing from the spirit and scope thereof. It should therefore be understood that the claims are not to be considered as being limited to the precise embodiments set forth above, in the absence of specific limitations directed to each embodiment.
