We had enable MPLS on IP network. In our network we are having Gibic, Fastethernet and Serial (E1) connectivity. Using MPLS MTU 9196 on the full LSP and ip tcp adjust-mss 1460 between PE-P & P-PE.
Our broswing performance dramatically degrade. Browsing became very slow, it is taking more time to load full web site though we have enough free internet bandwidth. There is no impect on FTP performance, can consume full assigned bandwidth using FTP.
Do not use "ip tcp adjust-mss 1460", it is only good for testing, masking the real issue, or perhaps on edge routers.
On core routers, this command is not a good one, it will reduce troughput of all traffic.
You're path mtu discovery (PMTUD) should be working. If it does not, try to see where the problem is.
With MPLS, the best practice is to configure the MTU on the interface to the real MTU value
and not change the mpls mtu any longer. PMTUD should kick in.
But what is the problem exactly, usually the hosts on the edge are connected through ethernet
and hence have an MTU of 1500. So, there should not be an issue as your core links have a higher MTU.
If the core links also have an MTU of 1500 (e.g. GigabitEthernet), then use PMTUD or lower the MTU
on the edge devices (routers or hosts).