802.1Qbp - Equal Cost Multiple Paths
The full title of this PAR is "IEEE Standard for Local and Metropolitan Area Networks---Virtual Bridged Local Area Networks - Amendment: Equal Cost Multiple Paths (ECMP)".
This standard specifies protocols, procedures and managed objects to support utilizing multiple possible next hop choices for frames within a single service in Shortest Path Bridging MAC Mode (SPBM) networks. This is accomplished by applying one of a set of standard functions per frame at ingress and using the result as an input to all subsequent choices among multiple next hops as the frame transits the SPBM network. These functions are selected to ensure that frames belonging to the same data flow take the same path. Frames belonging to other flows can take other paths. It is anticipated that a new Tag will be defined possibly including a Time to Live (TTL) field. The standard defines Connectivity Fault Management (CFM) enhancements that can be used to proactively monitor and diagnose the paths that data takes through the network.
This standard provides the additional capability to use many more equal cost paths than 802.1aq's current Equal Cost Tree (ECT) mechanism due to improved scaling properties with respect to network diameter. This standard would be used in conjunction with an 802.1aq based control plane and would use specific Base Virtual Local Area Network identifiers (B-VIDs) and new ECT-ALGORITHMs as defined by 802.1aq. This standard may include multipath function information and may use time to live (TTL) loop mitigation. Corresponding new EtherTypes would be used to identify the new Tag formats. It is expected that both the current 802.1aq ECT and ECMP would be used at the same time in the same network (for different traffic/service categories) but differentiated by B-VID. This standard enhances Connectivity Fault Management (CFM) to monitor and diagnose the richer connectivity provided.
As diameter and number of adjacencies grow the number of paths increases exponentially. In such richly connected networks ECMP in addition to ECT allows for better utilization in proportion to the state required. TTL augments loop mitigation in the face of hardware, software and design failures. An augmented SPBM with this capability addresses urgent customer requests to meet the above needs with a single protocol, a single data path and a unified Operations, Administration and Management (OA&M) suite.
| Status | PAR approved May 17th, 2011; Standard approved Mar 27th, 2014 |
| Editor | Ben Mackcrane |
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