Question : How to do that with SQL ?

Hello Gurus,
We are in the process of installing a new ERP that is under SQL 2005.

I need to have high availability concerning that ERP and I was considering of having a mirror/failover/cluster/replica of my SQL Box on a remote off-site location.

But I need to be online with both Boxes , meaning that all Transactions are commited to SQL1 are then replicated to SQL2.
SQL2 will not be active unless SQL1 dies.

Which version of SQL does that ? and how it is done ?
How much bandwidth do I need ? a 512KB connection is enough ? or I need more ? How do I calculate how much I need ?
thanks gurus.

Answer : How to do that with SQL ?

what is miroring ?
what is clustering ?
what is replication ?
Check out microsoft documentaion on all those topics; there well explained on MS website or technet.
Mirroring:
http://technet.microsoft.com/en-us/library/cc917680.aspx
http://msdn.microsoft.com/en-us/library/ms188712.aspx
Clustering:
http://msdn.microsoft.com/en-us/library/ms179530.aspx
Replication:
http://technet.microsoft.com/en-us/library/ms151198.aspx

Mirroring is the easiest and less cost solution to implement;on top of that, it is the suitable solution for you according to what you described in your first post.