Thread Links Date Links
Thread Prev Thread Next Thread Index Date Prev Date Next Date Index

[802.3_10SPE] Multidrop topology - understanding check

As promised on the ad hoc call, here is my understanding of Stefan Buntz’s multidrop topologies:


Assume: ‘head node’ is as discussed in EPON – this is the node that controls the multipoint protocol.  All other nodes are clients.


Passive Linear:

                Stub length < 100mm

                Overall length, including < 25m

                Minimum spacing between nodes: 500mm

                Maximum spacing between nodes: 7900mm (8 m including 2 100mm stubs)

                Maximum number of nodes: 8 (including head node)

                No other constraints on node placement (no constraint on granularity)


David Brandt variation for industrial:  45mm shortest between nodes on linear topology.



-          Does minimum spacing include the stub lengths?

-          It appears from slide 4 that there may be minimums on overall length (8m) and stub length (50mm) – is this true?

-          Would a terminator be placed at the far-end, or at the head-node?

-          Is the ‘head node’ always at one end?


Passive Star:

                Head stub length (head node to passive star center) < 100mm

                Maximum star branch length – 7900m (8m including head-node stub)

                Minimum star branch length – 1000mm

                Maximum number of nodes – 8 (including head node)

                One node per branch    

No constraint on the granularity of branch length



                Is the minimum head stub length > 50mm

                Maximum total cable length – is this constrained?  7900 x 7 + 100 = 55400 mm (~55m) – is this correct?

                Placement of termination – at head end, distributed, or on one end of a linear

                What MDI return loss might be assumed at the branch ends? (100BASE-T1?)


George Zimmerman, Ph.D.

President & Principal

CME Consulting, Inc.

Experts in Advanced PHYsical Communications