Ring Topology Token Passing

Ring Topology Token Passing

Step through logical ring token passing, bounded access delay, frame return, and single-link fault behavior

animation
ring-topology
token-passing
mac
networking
intermediate
A guided ring topology workbench for seeing how a token controls transmission, why collisions are avoided, and where ring fault tolerance depends on the design.
Animation Intermediate Logical ring Token passing

Ring topology token passing workbench

Watch a free token circulate around a logical ring. When the selected sender receives the token it is allowed to transmit one frame, the destination copies the frame, and the sender removes the returning frame before releasing the token again.

Free token Current network state
10.4 ms Worst-case access delay
12.5 ms Loaded token cycle
Healthy Fault tolerance result
TryChoose Balanced load, set Nodes in ring to 8 and Token holding time to 2 ms, then press Play.
ObserveThe Token owner and Worst wait readouts advance around all 8 nodes while the Collision count remains 0.
ExplainWith one token and a 2 ms holding limit, only its current owner may transmit, so serialization prevents collisions but adds rotation delay.
Technical boundariesThe timing model assumes one logical token, fixed frames, and reliable links; it excludes token loss recovery, propagation jitter, queue distributions, cabling faults, duplicate tokens, and vendor MAC overhead.
Colour keynetwork topologies identitycurrent / primaryreference / datasuccesscautionerror / failure

What is moving?

The yellow token is permission to transmit. The purple frame is real data that must return to the sender so it can be removed from the ring.

Why no collisions?

Only the node holding the token may send. Other nodes listen and forward, so two stations do not intentionally transmit at the same time.

Try first

Press Step until the token reaches the sender. Then change node count and token holding time to see why the delay bound changes.

Important caveat

This is a logical ring model. Classic IEEE 802.5 was often cabled as a star through a MAU, and IoT token protocols may use a bus while keeping a logical token order.

Stage 1

Free token circulates Each node gets a predictable chance to transmit when the token arrives.

Stage 2

Sender captures token The sender changes the free token into a data frame for one destination.

Stage 3

Frame is copied and returns The destination copies the frame, but the frame continues until the source removes it.

Stage 4

Fault response depends on design A single ring can stop at a break; a protected dual ring can often wrap around one fault.

Control the ring

Use presets for common teaching cases, or adjust the ring manually.

6
2.0 ms
240 B
16 Mbit/s

The timing numbers are simplified classroom estimates. They are useful for seeing relationships, not for certifying a real deployment.

Interactive workbench

A free token is moving clockwise. The sender must wait until it owns the token.

Single ring Clockwise path
Logical ring topology token passing animation Nodes arranged in a ring with a yellow token and a purple data frame moving between selected sender and destination. Logical ring view: physical cabling can be star, ring, or bus depending on the protocol.
Token Data frame Active path Broken link

Token holder

Node 0 Only this node has transmit permission right now.

Frame progress

Waiting The data frame appears only after the sender captures the token.

Access rule

One sender Token ownership serializes access and prevents intentional collisions.

Healthy single ring. The sender is waiting for the token; increasing node count or token holding time increases the access delay bound.

Current packet story

The token is free. Every node forwards it until the selected sender receives it.

Step 0

Event log

Use this like a packet trace. It shows what a learner should notice after each step.

Quick reference

Token

A small control frame that grants send permission to the node that currently holds it.

Logical ring

The order in which nodes pass the token. It may not match the physical cable route.

Bounded delay

With one token and a hold-time limit, a busy node can estimate the latest time it should get access.

Dual ring

A protected design can wrap around a single break. Multiple faults can still partition the network.

Guided practice

Beginner path

  1. Press Step until the sender captures the token.
  2. Watch the destination copy the frame, then watch the frame return to the source.
  3. Raise node count from 6 to 10 and compare the worst-case delay.

Diagnostic path

  1. Choose Single break and notice where the token stops.
  2. Switch to Protected dual ring and compare the diagnosis.
  3. Use the formula trace to explain why this is still not infinite reliability.
Technical accuracy notes

What the model includes

  • One free token, one sender with queued data, one destination, and a finite token holding time.
  • Frame copying by the destination and frame removal by the source after the frame returns.
  • A simple worst-case access delay estimate: (N - 1) x THT + propagation.
  • Single logical ring failure versus protected dual ring wrap-around for one break.

What real standards add

  • IEEE 802.5 includes monitor functions, priority and reservation bits, timers, error handling, and management details not shown here.
  • FDDI used counter-rotating rings with wrapping behavior; this model only shows the concept.
  • BACnet MS/TP and PROFIBUS use token passing in building or industrial networks, but their physical media and timing rules are not identical to IEEE token ring.
  • Propagation delay in short IoT links is usually small compared with hold time, but the model still includes it so the formula is visible.
Primary source links