Spanning-tree Protocol implementation

Hello

Linux kernel has its own implementation of the spanning tree, it comes along with the bridge functionallity. Many Layer2 switch vendors ship their SDK (full sources, inlcuding Linux kernel), implementing VLAN, ACL etc. functions as well as STP.

What is the point of doing this? Is Linux's STP implementation not entirely

802.1d compliant, or not scalable? Or is it a specifics of the Linux' networking stack architecture? Thanks.
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Mark
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Mark
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ong

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Their STP implementation has to hook in with their hardware acceleration. The Linux STP implementation is designed to bridge network interfaces. A typical switch STP implementation bridges switch ports which normally don't present as network interfaces to the OS.

For example, when a packet arrives on a network interface, typically the network interfaces passes it to the operating system. But a switch will often only present a single network interface to the operating system. So how would the OSes STP implementation know which port an STP packet was received on unless there was some custom logic to interface with the switch ASIC?

So the short answer is that the two implementations are adopted to completely different purposes. However, you can fairly trivially turn one into the other. All you need is a special hook to tell the switch ASIC to pass all STP packets to the OS along with an identifier of which port they were received on and a special hook to allow the OS to control which switch ports are in forwarding states and which are in blocked states (often on a per-VLAN basis on both counts).

DS

Reply to
David Schwartz

[skip] Thanks, it sounds as a clear and straighforward explanation. I think the same reasons apply to vendor-implemented VLAN functionality vs. kernel native VLAN.
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Mark
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Mark

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