Server Connection Issue

[7thfleet]

My server(Its hosted) has been lagging more than normal today, and and about every 30 mins or so, it kicks everyone on with this in the server console:


09.10 10:25:06 [Server] INFO at sun.net.www.http.HttpClient.New(Unknown Source)
09.10 10:25:06 [Server] INFO at sun.net.www.http.HttpClient.<init>(Unknown Source)
09.10 10:25:06 [Server] INFO at sun.net.www.http.HttpClient.openServer(Unknown Source)
09.10 10:25:06 [Server] INFO at sun.net.www.http.HttpClient.openServer(Unknown Source)
09.10 10:25:06 [Server] INFO at sun.net.NetworkClient.doConnect(Unknown Source)
09.10 10:25:06 [Server] INFO at java.net.Socket.connect(Unknown Source)
09.10 10:25:06 [Server] INFO at java.net.Socket.connect(Unknown Source)
09.10 10:25:06 [Server] INFO at java.net.SocksSocketImpl.connect(Unknown Source)
09.10 10:25:06 [Server] INFO at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
09.10 10:25:06 [Server] INFO java.net.UnknownHostException: session.minecraft.net
09.10 10:25:06 [Server] INFO at iu.run(SourceFile:130)
09.10 10:25:06 [Server] INFO at java.net.URL.openStream(Unknown Source)
09.10 10:25:06 [Server] INFO at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
09.10 10:25:06 [Server] INFO at sun.net.www.protocol.http.HttpURLConnection.connect(Unknown Source)
09.10 10:25:06 [Server] INFO at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
09.10 10:25:06 [Server] INFO at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(Unknown Source)
09.10 10:25:06 [Server] INFO at sun.net.www.http.HttpClient.New(Unknown Source)
09.10 10:25:06 [Server] INFO at sun.net.www.http.HttpClient.New(Unknown Source)
09.10 10:25:06 [Server] INFO at sun.net.www.http.HttpClient.<init>(Unknown Source)
09.10 10:25:06 [Server] INFO at sun.net.www.http.HttpClient.openServer(Unknown Source)
09.10 10:25:06 [Server] INFO at sun.net.www.http.HttpClient.openServer(Unknown Source)
09.10 10:25:06 [Server] INFO at sun.net.NetworkClient.doConnect(Unknown Source)
09.10 10:25:06 [Server] INFO at java.net.Socket.connect(Unknown Source)
09.10 10:25:06 [Server] INFO at java.net.Socket.connect(Unknown Source)
09.10 10:25:06 [Server] INFO at java.net.SocksSocketImpl.connect(Unknown Source)
09.10 10:25:06 [Server] INFO at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
09.10 10:25:06 [Server] INFO java.net.UnknownHostException: session.minecraft.net
09.10 10:25:06 [Server] INFO Disconnecting tman11233 [*Ip removed*]: Failed to verify username! [internal error java.net.UnknownHostException: session.minecraft.net]
09.10 10:25:06 [Server] INFO Disconnecting tman11233 [*Ip removed*]: Failed to verify username! [internal error java.net.UnknownHostException: session.minecraft.net]
09.10 10:25:05 [Server] INFO tman11233 [*Ip removed*] lost connection
09.10 10:24:38 [Server] INFO tman11233 [/*Ip removed*] lost connection
09.10 10:24:23 [Server] INFO [ClearLag] Removed 10 Entities!
09.10 10:24:18 [Disconnect] User ~Owner___7thfleet___ has disconnected, reason: unknown
09.10 10:24:18 [Disconnect] User ~Moderator_tman11233 has disconnected, reason: unknown
09.10 10:24:18 [Server] INFO Unloading Player: tman11233
09.10 10:24:18 [Disconnect] User tman11233 has disconnected, reason: disconnect.endOfStream
09.10 10:24:18 [Server] INFO Unloading Player: 7thfleet
09.10 10:24:18 [Disconnect] User 7thfleet has disconnected, reason: disconnect.endOfStream
09.10 10:24:18 [Server] INFO Error: Player not found.
09.10 10:24:18 [Server] WARNING Can't keep up! Did the system time change, or is the server overloaded?
09.10 10:23:47 [Server] INFO §r<~§1§o§nOwner___7thfleet___§r> laggg
09.10 10:23:24 [Server] INFO [Metrics] mcstats.org
09.10 10:23:24 [Server] INFO [Metrics] mcstats.org

It has 2 GB RAM, and has about 1-3 players on it when it does this. We all have premium accounts.

 

[GuildMaster]

Failed to verify username! [internal error java.net.UnknownHostException: session.minecraft.net]

That could be it. Even if you have premium accounts, Minecraft will check for them through session.minecraft.net and login.minecraft.net.
Make sure your server doesn't block access to these 2 sites, also check they are not down through https://help.mojang.com/.
Basically, when you log in, Minecraft send the password and username to login.minecraft.net. Then it tells session.minecraft.net you are online.
Each 30 mins or so, session.minecraft.net checks you are still online. That is done to prevent people from stealing your account or playing at the same time on the same account.
Since it's hosted, you should also contact your host or see if they have issues.