Cisco − Understanding Multiple Spanning−Tree Protocol (802.1s)
Switched networks must fulfill stringent robustness, resiliency, and high−availability requirements. With growing technologies such as voice and video over IP, fast convergence around link or components failures is no longer a desirable characteristic, it is a must. However, until recently, redundant switched networks had to rely on the relatively sluggish 802.1d STP to achieve those goals. This often turned out to be the network administrator's most challenging task, as tuning the protocol timers was the only way to get a few seconds of the protocol, but often at the detriment of the network's health. Cisco has released many 802.1d STP augmentations such as uplink fast, backbone fast and portfast, features that paved the way toward faster spanning−tree convergence. Cisco also answered large Layer 2−based networks' scalability issues by developing the MISTP. The IEEE recently decided to incorporate most of these concepts into two standards:
- 802.1w (RSTP)
- and 802.1s (MST).
Using these new protocols, convergence times in the low hundreds of milliseconds can be expected while scaling to thousands of VLANs. Cisco remains the leader in the industry by offering the two protocols along with proprietary augmentations in order to facilitate the migration and interoperability with legacy bridges.
From svetulcho.org
