Smart Spanning Tree Bridging for Carrier Ethernets

Carrier Ethernet WAN transport services are taking off rapidly and the simplicity, ubiquity, and plug-and-play features of Ethernet are some key success factors. Originally, these transport services assumed the use of VLANs and spanning tree protocols within provider bridge (PB) and provider backbone bridge (PBB) networks. Because the existing spanning tree protocols (STP, RSTP, and MSTP) were deemed inadequate for carrier networks, very recently, a new class of shortest path routing solutions have been introduced that avoid the use of spanning tree protocols in the core namely, shortest path bridging (SPB) and shortest path backbone bridging (SPBB). As a proof of concept, this paper aims at illustrating that we can still use spanning trees in carrier Ethernets provided that the tree generation and VLAN-spanning-tree mapping are performed adequately. We call our solution smart spanning tree bridging (SSTB). SSTB can be used to enhance the 802.1s MSTP, without requiring significant changes in the current Ethernet equipment. Using very simple but yet realistic numerical examples, we show that SSTB yield near optimal bandwidth and link usage. We also show that SSTB outperform SPB in terms of service delivery, frame loss and jitter, while being comparable in terms of bandwidth usage and latency.