New MPLS infrastructure - network diagram for FE/BE, multiple sites

thanks for the response giltjr

I will be making a call to AT&T tomorrow, and I will ask those questions. Anything else I should ask?

You should be able to ask for a diagram of what the network will look like.

You need to decide how much bandwidth you need for backup.  Will ISDN do?  Or do you need more that 128 Kbps?

What you may want to look at is something like:

   "AT&T Mananged Router" <----> EVPN Cloud <----> "AT&T Managed Router"
                    /\                                                                               /\
                     |                                                                                 |
              Internet Link                                                              Internet Link
                     |                                                                                 |
                    \/                                                                                \/
          AT&T Managed Firewall   <---- Internet ---->   AT&T Managed Firewall
                                                  <-- VPN Tunnel -->

Your private traffic would flow over the EVPN cloud and normal Internet traffic would flow over the Internet.  If the EVPN link went down the site to site traffic would flow over the VPN tunnle over the Internet.  The only single point of failure is the router at each site.  However I think they even have options where you can have two routers at each site, one for EVPN and one for Internet with VPN over the Internet.  Primary link would be EVPN router and EVPN link, backup for site to site would be Internet and VPN tunnel.

AT&T has a TON of options, they all cost money, but they have tons of options.

thanks for the reply. The backup has to be seamless, so speed will have to the the same. And speed will have to improve over what we currently have, which are T1's from MCI/Verizon.

I will be asked about the single point of failure of having AT&T be the only supplier. Is there any way around that? If money can solve that problem, I'm all ears.

Will we have to add another firewall in front of the managed firewall for the FE/BE of Exchange?

Well technically AT&T could be a failure point, but that would mean their network would have an issue.  What are the chances of AT&T's network having a melt down?  Well not only is it slim to none, most of the biggies actually share backbones and connect to each other at peering points.

AT&T MPLS can get into the multiple T1, Fractional DS3, Full DS3, and so on all the way up to a full OC3.

Well if expense is truly no problem get two "MLPS" type connection at the same speed, one from MCI/Verizon and one from AT&T and do your own private BGP routing across the two.

However, you may still have a single point of failure.  How does the local telco get to your building?  Most likely one conduit with multiple wires/fiber into one telco closet.   What happens if the telco closet looses power, get distroyed, or the one conduit to your building gets cut.

Your best bet may be to just say we are going to use both Verizion Business and AT&T, one link from both at the same exact speed.  Get them both and your local telco in a room and say design it.  No bickering over who is primary and who is backup, infact design it so that traffic can flow over BOTH links at the same time.

They will be delivering two routers as you said, one for the EVPN and one for the Internet. I believe the managed firewall is not the best option if we are building a Front End/Back End for Exchange, as we'll need access to the firewall. They politely laughed when I asked for access to their routers.! So I assume the same for the firewall.

I am wondering what protocols are used on and between the two routers.