IP Networks: Spine leaf topology and where/ when to use Boundary clocks vs Transparent clocks

 

Boundary Clocks (BC) – take the PTP load of the grandmaster clock

  • - Yes, since the BC essentially isolates the Grand Master Clock (GM) from the next layer down. 

Transparent Clocks (TC) – will help with timing and increased network hops

  • - TC and BC both do the same here - both provide the same timing capability.

 BC provides good monitoring capability, They have the info about message rates, the accuracy of the clock that we're receiving, network delays etc. You can use BC to provide security, and to change the message rates to slaves.

 

TC are sometimes used in BIG spine devices or Monolithic architectures because BC's have a software stack (with hardware timestamping). This leads to a finite number of slave loads. Most TC when using one-step mode however use all hardware, so no slave count limit.

*“ TC is sometimes used in BIG spine devices or Monolithic architectures because BC's have a software stack (with hardware timestamping). This leads to a finite number of slave loads.

 Explain: Unless you’re using a really big chassis err towards using Boundary Clocks.

 What does really big mean? If you had more than 350 Slave Clock hosts (end points that are receiving PTP) attached, use TC rather than BC

 Remember that if you use TC, the GM needs to be able to support the number of end points.

 

  1. For large Campus style networks people tend to put the TC in the Spine device / layer and BC in the leaf

 2. For a simple 1 or 2 switch network  with a high slave count (>300) from single switch– use TC

  • only limitation is the amount of slaves the PTP GM can handle