MCSv6 with NAT and Firewall Traversal Solution

MCSv6 introduces a new Network Address Translator (NAT) traversal solution that allows clients behind NAT to automatically send and receive multimedia data. The solution transientsly detects the user's settings and allows the user to successfully send and receive data.

Researchers:
Assoc. Prof. Sureswaran Ramadass
Dr Omar Amer Abouabdalla
Azlan Osman
Iznan Hasbullah
Tan Chen Wei
Salah Noori Saleh
Ayman Helweh-Hannan
Usman Sarwar
Phang Tze Shu
Arnaud Jean Joseph MARTIN

MCS NAT Traversal Solution

MCSv6 introduces a new Network Address Translator (NAT) traversal solution that allows clients behind NAT to automatically send and receive multimedia data. The solution transientsly detects the user's settings and allows the user to successfully send and receive data.

A NAT maps a private address and a port to a public address and a port. Generally, the public address and the port are dynamically assigned to the client each time the client connects to the Internet. The mapping is kept in a session while the client sends requests to the Internet. When the client becomes inactive, the session will be terminated after a time period defined by the NAT configuration. After the session is ended, if the client sends a new request using the same port and the same IP, the NAT could assign a different port to this client.

Since UDP does not guarantee packet delivery, the solution uses internal acknowledgement technique to ensure that the initialization packetwhich establishes the NAT session is received by the server and that its response is received by the client

UDP is a connectionless protocol; hence the NAT does not know when the session is finished. NAT terminates the session if the server and the client fo not exchange any data for a specific timeout period. The timeout period is typically between 30 seconds to 1 minute. However, the NAT administrator may change the timeout period.

MCS NAT traversal solution solves the timeout problem by sending a “keepalive” packet from the client to the server to keep the session alive. When no data packets are being exchanged, the client sends and empty “keepalive” packet to the server. Since the packet is empty, it will keep the session from being terminated without overloading the network.

MLIC (Multiple LAN IP Converter) maintains a table for the ports opened in NAT for each conference and for each NATed client. This is done during the NAT session initialization of each port.

MCS Firewall Solution/Configuration

MCSv6 utilizes a new firewall solution that automatically works with the default settings of most firewall systems. For most users, MCS will transiently connect through the firewall without any changes. However, if the firewall settings are strict, the user/administrator must open certain ports for MCS.

Contact
Assoc. Prof. Sureswaran Ramadass

Published: 19 Nov 2006

Contact details:

Universiti Sains Malaysia 11800 Minden Penang

++604-6533888 (Main Campus), ++609-7651704/00/11(Health Campus), ++604-5937788 (Engineering Campus)
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