Firewall

We access the Citrix Server on Remote network using the Citrix Client. this citrix server is behind the firewall. the firewall allows only the specified IP Address. Since we are accessing through Dial Up account our dial out IP address keeps on changing, each time we dial we get a different IP Address. is there any other way for a firewall, other than verifying the IP address to allow access. i mean i don’t want that firewall to look for IP address to allow OR to deny the access , instead is there any other parameter
that a firewall can look for before giving access.