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Cached TCP Mechanism

Since the control messages are critical to the connection management scheme, it is important that these messages do not get lost or corrupted in the network medium. So, it was decided to facilitate the exchange of information over a reliable transport protocol like TCP. But along with the added reliability, there is a tremendous overhead accrued for opening and closing TCP sessions for every message sent. Thus it was decided to implement a caching mechanism, to transmit TCP packets. Caching meant that the daemon process at startup opened a TCP connection to all the hosts it would communicate with and use that connection to send messages throughout the duration of the connection establishment process. Since the HEC only communicates with the SEC of the switch it is connected to, it just opens a TCP socket to that SEC. It uses this socket to send all messages meant for that SEC. An SEC on the other hand, has to maintain a list of active socket connections. An SEC opens TCP socket connections with every neighboring daemon - both SECs and HECs. This mechanism drastically improved the connection establishment times. The experimental results are detailed in Section 6.



Riccardo Bettati
Fri Jul 11 18:14:48 CDT 1997