Incremental BackUp in sql server

I got a task for backing up my clients data through internet. Client has about 50gb of data there. So I need to back up the data and pass through internet, But it takes about 8 to 9 hours for this process, Because our internet is slow. So I cant resolve client issues in time. So I decide to change my back up strategy. I tried differential backup. It solves some what my problem but not. Because it take back up from previous full back up. So I tried to implement Incremental backup. I know this will solve my problem. But sql server doesn't support incremental backup.

So please help me if there any way to resolve my issue. Also tell me why there is no incremental back up in sql server. But DB2 has.

I am using SQLSERVER 2008 R2 database