Resiliency using multiple E1's and routing Voice

[dave_miller]

We currently pass voice over a dedicated single E1 link to a remote site, this is backed up by ISDN PRI. The remote site is now expanding and has the potential this year to require at least 6 - 8mb's worth of bandwidth to support the increase in call requirements. Using multiple E1's, likely backed up by some form of satelite connection (1 to 1 basis - so 6 - 8 Mb satelite bandwidth) what is the best option for aggregating the E1's to load balance the bandwidth allowing for single E1 failure (through use of different local loop providers where possible) and cut over to resilient connections maintaining max possible uptime. Ideas so far revolve around use of OSPF/BGP (trying to avoid fragmentation of the voice packet through dual path routing - can do this with destination IP method) or bundling the E1's & the backup circuit into a single link allowing for degraded mode in the event of single E1 failure.

Hardware is currently dual 3745's at either end in an HSRP setup E1 primary & ISDN PRI backup.

Any suggestions welcome.

[nathan.deane]

Ok,

Surely for the price of a 6 - 8Mb connection which will either be an Ethernet circuit or a 34 Mb SDH bearer you may aswell purchase a 2 site MPLS VPN. Obviously this will determine on th edistance between your 2 sites?

what is the current packet size for your Voice ? you may want to think about compressing it down with a codec G.729 ?

[dave_miller]

We currently use G.729a for our codec - giving us approx 140 calls per 2mb (in the 75/25% standard) and using RTP compression. MPLS was considered but with the added overheads and potential instability using RTP the preference is point to point. Problem is that for one region E3 ports are not possible due to the restrictions on the local infrastructure.

Really looking for ideas on best way to provide redundancy for multiple E1 circuits (HSRP, load balanacing using OSPF/BGP/eIGRP, aggregation of the E1's etc etc) and any potential pitfalls we may come across .. basic setup is primary 3745 houses 3+ E1's secondary 3745 houses equivalent bandwidth as backup.