I`ve been asked to look into Cluster over the WAN for a particular site though I don` recommend it .
From Cisco SRND Set up
ICCS- call traffic
We have 2x server for around say 300 -500 user in two buildings - A & B. Cisco states that for below 10k BCHA then you need 1.544Mbs for ICCS or based upon a formula if you have more then 10KBCHA -
Total BHCA/10000 *(1+0.006*Delay )
A T1 * per server in each remote location i.e Site 1 Publisher, Site 2 Subscriber and a TFTP/MOH so Site 2 requires T1*2 (Sub and TFTP) to the central site
Obviously 10k BHCA is quiet a large through put what if you only have a small number of phones 300-500 which will provide less then the 10K. Is there a different formula for less then 10K for ICSS, is the T1 still a min. requirement
If you configure CUCM so that each site is designed - admittedly not good practice, but to only have the phones to register to the "sites" CUCM server so to restrict call traffic between the two sites again is the T1 a minium again. obvious if you use EM then this effect this set up .
I`m being asked by support these questions purely based upon a SI who has suggested splitting the two server Cluster across two sites which only has a 10 Mbs link between them which is being used by data as well and that the back up link is only 2Mbs, My recommendation is to have the two CUCM servers in Site A and have the necessary SRST router in place in Site 2 and have the phones register to Site A as 1st and 2nd choice with 3rd choice the SRST router. But I would like to understand the requirements a bit more - is there any movement the sizes mentioned above, Cisco SRND
Based on the SRND we would require a min 2x T1 or 3Mbs
ICCS - 1.544Mbs
Databas 1.544Mbs based upon a single remote server