CAN Communications | Network Topology

Network Topology

Network Topology refers to the manner in which nodes on a bus are interconnected.

The most common automotive network configurations are:

  • Ring or loop
  • Star
  • Ring-star hybrid
  • Bus
  • Tree

An understanding of the topology of the vehicle network is critical when attempting to diagnose bus communications errors. The topology of the network can provide clues as to how various nodes interact with one another. Topology information is found in vehicle data line wiring schematics.

Ring Configuration

This diagram illustrates a ring network configuration. PC #1 is connected directly to the server. PC #2 connects to PC#1 and so on. PC #8 completes the ring by connecting directly to the server.

Ring Configuration

Ring Configuration Wiring Diagram

This is an example of a GM LAN low speed ring or loop configuration network. The BCM is networked with eight other nodes in two separate ring configurations. The benefit of this topology is signal regeneration. As a signal passes from node to node it is amplified.

Benefits of the ring configuration include:

  • Built-in redundancy

    In this 2-wire network if one wire fails, communication can continue on the second wire.

  • Signal regeneration

    The data transmission is amplified as it passes from node to node

Star Configuration

In a star configuration, all of the nodes are connected to a central point. This can be a node on the bus, a splice pack, a junction block or simply a hard splice in the wiring. A star configuration is typically found ion a single wire bus.

Star Configuration

Star Configuration Wiring Diagram

Here is an example of a GM class 2 star configuration. All of the nodes are connected to the splice pack. The splice pack is connected to the DLC and the BCM (through another connector not shown).

Benefits of the star configuration include:

  • Ease of diagnosis using the spice pack
  • All nodes on the bus are connected at one or more junctions
  • Easily expandable

The star topology is one of the simplest network configurations and is easily expandable, as additional nodes can simply be plugged into the bus.

Disadvantages of the star configuration include:

  • More wiring is necessary to connect each node to the central node
  • The star configuration offers no redundancy
  • If one wire to a node fails, that node drops off the bus
  • If the central node fails, the entire network fails

This post was written by: Martin Hand

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Martin Hand

About Martin Hand

ASE Certified L1 Advanced Mastertech. Martin Hand has over 15 years experience in Asian and European Import Auto Repair. Specializing in electrical diagnosis, engine performance, AT/MT transmission repair/rebuild. Martin is also pursuing a degree in Computers Science & Information Systems starting at Portland Community College while he plans to transfer to OIT. Certified in Java application level programming, experienced with other languages such as PHP, Ruby, JavaScript and Swift. Martin has future plans of automotive diagnostic software development.

5 Comments

  • Darrin Marshall says:

    Hello, I am a GMASEP instructor at the university of Alaska. I have the opportunity to coach Alaskan high school instructors, counselors, and administrators. I will have them for 3 hours where I’d like to promote the automotive world and the need for educated technicians. I will be taking about the advanced world of multiple computers on multiple networks and how one computer on h.s. can talk to a computer on l.s.(along with many other aspects)

    I feel it would be a huge asset to have a visual to illustrate my point. I would greatly interested in any help.

    • Martin Hand Martin Hand says:

      You can use any of our information for your educational use, thank you. Go to contact us to email me if you have any other questions. My comments post are usually delayed because I’m always so busy have hard time maintaining the website

  • would you please send me the communication diagram of control unit in new Nissan cars.
    regards

  • please send me the communication diagram of control unit in new nissan

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