Lag on servers

When I open my minecraft on the latest snapshot I can instantly notice that the private server that I have is very laggy.

What I expected to happen was...:
I expected that there wouldn't be that much lag.

What actually happened was...:
There was a lot of lag.
Steps to Reproduce:
1. Open minecraft on 13w42a/b
2. Enter any private server hosted on the computer you play on
3. If recreating the bug is successful you will notice a lot of lag