Fault tolerant communication in a TRILL network

#1. Technical Field

#The present invention relates in general to data networks, and in particular, to a link aggregation group (LAG) for a Layer 2 data network, such as a Transparent Interconnection of Lots of Links (TRILL) network.

#2. Description of the Related Art

#FIG. 1 is a high level block diagram of an conventional TRILL campus in accordance with the prior art;

#FIG. 2 depicts an exemplary network environment in which a network node external to a TRILL campus can be connected to multiple RBridges (RBs) in the TRILL campus via multiple redundant links forming a LAG;

#FIG. 3 illustrates an exemplary network environment in which a TRILL RB handles ingress and egress traffic for multiple RBs coupled to a TRILL campus via t-LAGs;

#In the drawings, common reference characters are utilized to identify like or corresponding features.

#The present application describes mechanisms and associated methodologies, referred to herein as TRILL LAG or t-LAG, that facilitate the connection of network nodes (e.g., servers and/or switches) external to a TRILL campus in a Link Aggregation Group (LAG) through the use of a virtual routing bridge (virtual-RB). Multiple t-LAGs may additionally be hosted by a set of multiple physical switches, herein referred to as a t-LAG cluster, with all t-LAGs in a given t-LAG cluster preferably (but not necessarily) sharing the same virtual-RB. The use of the virtual-RB for the t-LAGs can resolve load distribution for unicast (UC) traffic. For multidestination (e.g., multicast (MC), broadcast (BC), destination lookup fail (DLF)) traffic, different mechanisms are employed to ensure traffic is properly delivered to a peer RB of a t-LAG cluster; otherwise, either more than one copy of a multidestination frame may be sent to the same destination or a frame may be erroneously returned to an external network node that sourced the frame via the same t-LAG at which the frame ingressed the TRILL campus.

#It is presently preferred to separate the traffic forwarding in a t-LAG cluster into two domains: the TRILL routing domain and the regular L2 switching domain. That is, it is preferred if the data switching in the regular L2 domain in a t-LAG cluster is handled within the virtual-RB itself and does not go through TRILL routing at all, if possible. An interswitch link (ISL) for a t-LAG cluster can advantageously be used for frame redirection in the regular L2 switching domain in the event of a link failure on any t-LAG in the t-LAG cluster.