How to keep tunnel alive for 24 hours. In my case VPN getting disconnected every 55 min

NEVPNManager how to keep tunnel alive for 24 hours. In my case Tunnel comes down every 55 minutes when connected to a VPN port.I am just trying to keep the tunnel active as long as possible.

This my configiration

NEVPNProtocolIPSec *protocalConfigurationIPSec = [[NEVPNProtocolIPSec alloc] init];

protocalConfigurationIPSec.username = "user name";

protocalConfigurationIPSec.passwordReference = passwordReference;

protocalConfigurationIPSec.serverAddress = @"ipaddress";

protocalConfigurationIPSec.authenticationMethod = NEVPNIKEAuthenticationMethodSharedSecret;

protocalConfigurationIPSec.sharedSecretReference = sharedSecretReference;

protocalConfigurationIPSec.localIdentifier = @"userGroup"

protocalConfigurationIPSec.remoteIdentifier = @"mobile"

protocalConfigurationIPSec.useExtendedAuthentication = YES;

protocalConfigurationIPSec.disconnectOnSleep = NO;

manager.protocolConfiguration=protocalConfigurationIPSec;

[manager setOnDemandEnabled:NO];

[manager setLocalizedDescription:@"VPN"];

manager.enabled = true;

how to pass keeplive to the vpn server.

Thanks