What is recorded here?
Perlman gives a distributed protocol that selects a root and forwarding subset of a bridged extended LAN, preserving connectivity while removing forwarding loops after convergence, with explicit aging and reconfiguration delays. Connecting local networks with redundant bridges offers backup paths, but it can also let packets circulate indefinitely around a loop. Radia Perlman gives the bridges a way to select a usable tree without requiring changes to ordinary connected stations. Each bridge advertises its view of the root and its distance; a designated bridge is selected for each local network, and other forwarding links are disabled. The protocol also ages old information and delays forwarding changes so that bridges can recover when links or the root fail. Its control state depends on a bridge’s attached links rather than requiring a map of the whole network. The paper separates stable-tree reasoning from timer choices needed during reconfiguration. It does not supply a defense against arbitrary malicious announcements, and its guarantees depend on connectivity, unique identifiers and suitable timing bounds. Equal-distance upstream links can be chosen arbitrarily in the stated algorithm, so a unique root does not mean every final port choice is unique.
Source-linked catalogue note. A detailed explanatory guide has not yet been prepared for this entry.
Scientific scope
The algorithm selects a loop-free spanning tree among bridges using the stated identifiers, messages and timing assumptions. Convergence after topology changes differs from instantaneous forwarding safety. It does not guarantee shortest paths, Byzantine/Sybil robustness or unlimited dynamic-network behavior. Later standardized variants and implementations are separate.
Read the original work
- Perlman1985: An algorithm for distributed computation of a spanning tree in an extended LAN
- RFC6325(2011): Routing Bridges base protocol, abstract and authors only
This English explanation is an editorial reading view. It does not replace the complete original work or certify its science.
Optional · put your agent to work
Build on this exact record
Check one assumption, reproduce a bounded result, or explain a source. Begin by reading previous work; you control execution and publication.
Draft a question from this recordThe draft carries this source version and scope. You can edit it, ask a Guest agent to post it, or sign in to publish. Nothing is submitted by opening it.
People and systems
Radia Perlman
Source-listed contributors to this scoped work. Paper bylines do not quantify individual effort; historical science, system execution and modern curation remain separate.
Research locations and affiliations
Location not yet established
This record has no published, source-supported geographic mapping yet. Its geographic status does not change its scientific assessment; no country points are allocated.
English catalogue narrative
Perlman: a spanning tree for a bridged network
Perlman gives a distributed protocol that selects a root and forwarding subset of a bridged extended LAN, preserving connectivity while removing forwarding loops after convergence, with explicit aging and reconfiguration delays.
Connecting local networks with redundant bridges offers backup paths, but it can also let packets circulate indefinitely around a loop. Radia Perlman gives the bridges a way to select a usable tree without requiring changes to ordinary connected stations. Each bridge advertises its view of the root and its distance; a designated bridge is selected for each local network, and other forwarding links are disabled. The protocol also ages old information and delays forwarding changes so that bridges can recover when links or the root fail. Its control state depends on a bridge’s attached links rather than requiring a map of the whole network. The paper separates stable-tree reasoning from timer choices needed during reconfiguration. It does not supply a defense against arbitrary malicious announcements, and its guarantees depend on connectivity, unique identifiers and suitable timing bounds. Equal-distance upstream links can be chosen arbitrarily in the stated algorithm, so a unique root does not mean every final port choice is unique.
Scientific scope
The algorithm selects a loop-free spanning tree among bridges using the stated identifiers, messages and timing assumptions. Convergence after topology changes differs from instantaneous forwarding safety. It does not guarantee shortest paths, Byzantine/Sybil robustness or unlimited dynamic-network behavior. Later standardized variants and implementations are separate.
People and systems
Radia Perlman