Dynamic optimization of a multicast tree hierarchy for a distributed switch

• US 8,958,427 B2
• Filed: 12/07/2012
• Issued: 02/17/2015
• Est. Priority Date: 03/14/2012
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Basso, Claude, Greenfield, Todd A., Walk, Bruce M.
• Primary Examiner(s): Cho, Un C
• Assistant Examiner(s): Lou, Peian
• Application Number:
  US13/707,658
• Publication Number:
  US 20130242990A1
• Time in Patent Office: 802 Days
• Field of Search: 370/252, 370/352, 370/353, 370/389, 370/390, 370/392, 370400-402, 370/428
• US Class Current: 370/400
• CPC Class Codes: H04L 12/18 for broadcast or conference , e.g. multicast
• CPC Class Codes: H04L 12/185 with management of multicast group membership

Abstract

A distributed switch may include a hierarchy with one or more levels of surrogate sub-switches (and surrogate bridge elements) that enable the distributed switch to scale bandwidth based on the size of the membership of a multicast group. Moreover, each surrogate may optimize the hierarchy according to one or more optimization criteria. For example, each surrogate in the hierarchy may have the necessary information to ensure that if the next surrogate in the hierarchy is unavailable, the data may be routed to a backup surrogate. The selected hierarchy may be further optimized by skipping surrogates (or a surrogate level) such that the data intended for a skipped surrogate is sent to a surrogate in a lower-level of the hierarchy. This may better utilize the connection interfaces in the transmitting sub-switches and eliminate any unnecessary surrogate-to-surrogate transfers.

Claims

1. A method of forwarding a multicast data frame in a distributed switch, comprising:

receiving a multicast data frame on a receiving port of an ingress switch in the distributed switch;

determining a first surrogate switch in a first level of a hierarchy, wherein the first surrogate switch is assigned in the hierarchy to forward at least a portion of the multicast data frame received from the ingress switch directly to a second surrogate switch in a second level of the hierarchy,

wherein the ingress switch has a direct physical connection to both the first surrogate switch and the second surrogate switch; and

upon determining that the first surrogate switch is unavailable because of an operational outage, ignoring a part of the assigned hierarchy by forwarding the portion in the distributed switch from the ingress switch such that the portion is received by the second surrogate switch without the portion being forwarded to any surrogate switch in the first level of the hierarchy.

2. The method of claim 1, wherein the ingress switch comprises a plurality of connection interfaces for forwarding the portion, wherein forwarding the portion in the distributed switch such that the portion is not forwarded to any surrogate switch in the first level uses a greater number of the plurality of connection interfaces relative to forwarding the portion in the distributed switch by forwarding the portion to the first surrogate switch in the first level.

3. The method of claim 1, wherein a number of levels in the hierarchy used to forward the portion in the distributed switch is set based on a multicast group associated with the multicast data frame.

4. A method of forwarding a multicast data frame in a distributed switch, comprising:

receiving a multicast data frame on a receiving port of an ingress switch in the distributed switch;

identifying a first surrogate switch in a first level of a hierarchy, wherein the first surrogate switch is assigned in the hierarchy to forward at least a portion of the multicast data frame received from the ingress switch directly to a second surrogate switch in a second level of the hierarchy,

wherein the ingress switch has a direct physical connection to both the first surrogate switch and the second surrogate switch; and

after assigning the first surrogate switch in the hierarchy to forward the portion to the second surrogate switch and upon determining that the first surrogate switch is unavailable because of an operational outage, ignoring a part of the assigned hierarchy by forwarding the portion in the distributed switch from the ingress switch such that the portion is received by the second surrogate switch without the portion being forwarded to any surrogate switch in the first level of the hierarchy.

5. The method of claim 4, wherein the ingress switch comprises a plurality of connection interfaces for forwarding the portion, wherein forwarding the portion in the distributed switch such that the portion is not forwarded to any surrogate switch in the first level uses a greater number of the plurality of connection interfaces relative to forwarding the portion in the distributed switch by forwarding the portion to the first surrogate switch in the first level.

6. The method of claim 4, wherein a number of levels in the hierarchy used to forward the portion in the distributed switch is set based on a multicast group associated with the multicast data frame.