Avocent Cyclades-PR2000 Mail Server Web Server, Port 25 Smtp, Mail Server Web Client

Cyclades-PR2000

An example showing the third type of traffic control is given in Figure 12.8. The network administrator wants to prioritize the access to his web server. He also wants to prioritize e-mail sent by his SMTP server, but the priority should be lower. All other traffic should have the lowest priority. For web server access, the important flow direction is not the user requests, but rather the data requested. The traffic control rule must be placed on link 2. In the case of e-mail, the important flow is the data leaving the e-mail server, and not the acknowledgements back. This is also governed by link 2. (Note: flow control could be placed on the data request packets and the SMTP acknowledgements by associating rules to link 1.)

E-mail Server

Web Server

Port: 80	Requests
	Requested
Data

		Port: Any
	Back	out
ACKs		-mail
		E
Link 2	PR2000
	Link 1
	INTERNET

Port: 25 (SMTP)

Port: Any

E-mail Server

Web Client

FIGURE 12.9 TRAFFIC RULE EXAMPLE 2

Chapter 12 - Filters and Rules 109