Backbone interconnections and uplink planning

[Safail Mulkumov]

Hello dear experts.

We are planning backbone network around 6 core router and 40 aggregation router. We plan to migrate 400K user to this network. Each user max speed is 20Mb. My question is that: is there have any formula to calculate the required bandwidth for backbone interconnections and especially for uplinks to support all user traffic? I know its impossible. But anyway i waiting for your valuable feedback.

Many thanks.

[Giuseppe Larosa · Accepted solution]

Hello Sefail,

400K users = 400000 users

6 core routers and 40 aggregation routers.

You will have 10000 users per aggregation router.

Allowing 20 Mbps per user would mean 20 Mbps * 10000 to the core from each aggregation router = 200 Gbps.

Now, accepting some overbooking like a factor 5:1 you finish to have 200/5 40 Gbps from each aggregation node to the core node(s).

40 aggregation routers connected to 6 core routers to two different core nodes means:

40/6  * 2  roughly 14 x 20 Gbps = 28 Ten Gigabit port just to connect the aggregation nodes per core node.

We have to add the links between core nodes now.

Le's suppose again that 20% of the traffic received from the downstream aggreg. nodes is destined to some destination attached to another core node.

You would need 20% of 28 TenGiga to reach the other core nodes, 6 Tengiga to each of the other core. Your core routers needs to support 30+28 = 58 Tengigabit ports.

Hope to help

Giuseppe