[c-nsp] Entering into MPLS

[Shawn Mesiatowsky]

We current are a smaller company reaching the brink of the enterprise
level. We currently have a data center at our head quarters, and 30
remote sites connecting with either a managed ADSL connection, or
through an VPN tunnel through the Internet. We are currently going to
move to an MPLS network. 5 remote sites have 10 users and are going to
be connected to the MPLS network via an ADSL or T1

15 remote sites only have 10 - 20 users and will have a 10 MB fiber
connection to the MPLS

8 remote sites have 30 users and will have a 10 MB fiber connection to
the MPLS

2 remote sites have 50 and 70 users and will have a 10 MB fiber
connection to the MPLS

1 site has 250 users and will have a 100 MB fiber connection to the MPLS

And HQ will have 250 users and have a 100 MB fiber connection to the
MPLS

 

We are also implementing VoIP in all the offices so we need some form of
QOS

 

We were looking at three options for MPLS

Option 1: layer 3 MPLS and share our routing info with our carrier

Option 2: layer 3 MPLS, and using GRE routes so we do not need to share
routing info

Option 3: layer 2 with QoS support

 

What size of routers do we need in our data center, and other main site?

Does GRE have much performance impact? And if so, do we need to go with
a larger router if we use GRE?

We are going to use integrated services routers in the remote sites to
support SRST, so we were thinking to go with 2801's for smaller shops,
to 2851's for the larger sites.

For the main site and data center, we were thinking of either 3845 or
7204vxr.

Would the 3845 do the trick? Or would we need to move up to the 7204vxr?

How exactly can we size our routers correctly? Do most people just
usually go with experience? Or use some form of specs? And what specs
should I be looking for?

 

Any suggestions or comments?

 

Thanks for your help