Enhanced Services
Active Networks promise a flexible and dynamic way of introducing new services into the network by simply programming the nodes on the network. The Authors of IPAN[6] developed two smart new services called mSMTP (meta SMTP) and mHTTP (meta HTTP) which reduce end-to-end network delays which in turn decrease the level of congestion in an Active Network.
The
sequence of messages traversing the network during mail transfer using
traditional SMTP is shown in Figure 7. The Acknowledgment messages (ACKs) are
time consuming as well as network resources to be routed to the destination. On
the other hand, mSMTP sends back only one Acknowledgment notifying the
user of a successful or failed message delivery.
Figure 7. Multiple End-to-End delays in a Traditional Network.[6]
Operation: A user sending mail using mSMTP embeds the mSMTP code in the body of a SmartPacket. As the SmartPacket traverses the Active Network, the domain of the current node is checked to determine if it is the same as the domain of the destination node. If the domains match then the code in the SmartPacket is executed on the node. The mSMTP code then initiates a normal SMTP service with the receiver and attempts to deliver the mail message to the destination as shown in figure 8.After the interchange is complete, an ACK/NAK is sent all the way back to the sender. If the message has to be sent to more than one user in the same domain, then multiple SMTP connections are spawned at the destination Active Node and only one ACK/NAK message is sent back to the sender. Thus instead of multiple ACK/NAKs going back and forth across the network, only a single reply is sent.[6]
Figure 8. Reducing End-to-End Delays using an Active Network[6]