Download start good to slow very slow, upload perfect

Hi all,
My problem is in edgerouter rb1100 with 6.1

Is connected with vlan/ppp autentication 100Mbps/100Mbps.

My problem is Download start good to slow:
example: 100mbps after 4,5second 20mbps and it’s floting 20/30/15 mbps.
Upload alway 100mbps.

Policy mange change MSS is dynamic but counter work only ppp set in “out interface”,instead policy mange change mss interface ppp set in “in interace”, counter alway 0

Ip fragmentation problem?

It could be a setting with the webserver you are downloading from. It may allow for an initial high burst and then reduce the speed… Does it happens with more than one web server?

did you download frm other site ? download almost 5 site for result . if this still down in all website then have some problem