B2B Integration : A Practical Guide to Collaborative E-commerce

304 B2B Integration — A Practical Guide to Collaborative E-commerce
others. These machines have the ability to cope with any threats
posed by outside requests.
2. Check the source of the traffic. For some types of incoming traffic,
it may be necessary to check the source. For example, users coming
in via TELNET may have to provide their username and password
or a personal token for identification.
3. Regulate not just the incoming traffic, but also the traffic going from
the internal LAN to the external Internet. If a network is compromised,
then it may be made to send certain data/packets to the outside
Internet to addresses where it is not supposed to go. Checking where
data is going from the inside to the outside can halt this kind of
activity.
4. Encrypting or checking data integrity for all the traffic to or from a
network. This 'gateway' type of implementation is also called a
virtual private network.
10.7.3. Types of firewalls
Firewalls generally belong to two classes: network level and application
level.
Network level firewalls
Network level firewalls intercept every packet that attempts to go in or
out of your network (see Figure 10.13).
A network level firewall acts at the IP — machine address level. It
uses screening routers or packet filters. Each network packet contains
External
Network
Di rect Tratt ic
Possible
Network
Laval
Bastion
[Optional)
,=t Ne
/ (Subnet)
Figure 10.13. — Network level firewall schematic