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New Member

STP/RSTP/MST in a Metro Ethernet ring

We are building a large Metro ethernet Network . The topology consists of BN ( cat 3550 switches ) on a GIG ethernet ring . We intend to use 14 Building node (3550)siwtches in the ring and then aggregate the Gigabit ring onto a 7609 at the Aggregation site .

Can anybody suggest whether I should use RSTP or MST and minimise the convergence/reconvergence period in cases of fiber cut on the ring .

Hrishikesh

  • Metro
5 REPLIES
New Member

Re: STP/RSTP/MST in a Metro Ethernet ring

Also please tell me what are the typical convergence periods on the ethernet rings on which you work ??

To waht level is the Voice and Video traffic affected

New Member

Re: STP/RSTP/MST in a Metro Ethernet ring

Of the two, RSTP is the simpler techonology, while

MST obviously scales better. There are more edge

cases to consider with MST, and we concluded it

needed lots more lab testing before we would be

comfortable with it. RSTP (in Cisco's Rapid-PVST

version) is very simple to deploy.

We are using Rapid-PVST everywhere we can.

New Member

Re: STP/RSTP/MST in a Metro Ethernet ring

Thanks Steinar ,

Does any of the fiber failures affect Voice/ Video services delivered on the Network .

What are the typical convergence times that you have experienced with RSTP

Hrishikesh

New Member

Re: STP/RSTP/MST in a Metro Ethernet ring

The re-convergence time using RSTP could be affected by the number of: nodes, mac addresses, vlans configured and L2 flows.

With 10 nodes, 400 vlans and 950 mac addresses, re-convergence has been measured to be around 1s.

Other scenario's may produce different results.

New Member

Re: STP/RSTP/MST in a Metro Ethernet ring

Then which one is the most important factor to determine the convergence time?

If I have scenario with 30 nodes, but only 1 VLAN and 200 MAC addresses, will the convergence time be dramatically increased or decreased?

Thanks!!

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