Tcp And Udp Based Services - D-Link NetDefend DFL-210 User Manual

3.2.2. TCP and UDP Based Services

To view a specific service in the system:
CLI
gw-world:/> show Service ServiceTCPUDP echo
The output will look similar to the following listing:
Property
-----------------
DestinationPorts:
SourcePorts:
PassICMPReturn:
MaxSessions:
Comments:
Web Interface
1. Go to Objects > Services
2. Select the specific service object in the table
3. A listing all services will be presented
3.2.2. TCP and UDP Based Services
Most applications are using TCP and/or UDP as transport protocol for transferring application data
over IP networks.
TCP (Transmission Control Protocol) is a connection-oriented protocol that, among other things,
includes mechanisms for reliable transmission of data. TCP is used by many common applications
where error-free transfers are mandatory, such as HTTP, FTP and SMTP.
Streaming Applications
For other types of applications where, for instance, performance is of great importance, such as
streaming audio and video services, UDP (User Datagram Protocol) is the preferred protocol. UDP
is connection-less, provides very few error recovery services, and give thereby much lower
overhead traffic than when using TCP. For this reason, UDP is used for non-streaming services as
well, and it is common in those cases that the applications themselves provide the error recovery
mechanisms.
TCP and UDP Service Definition
To define a TCP or UDP service in the D-Link Firewall, a TCP/UDP Service object is used. This
type of object contains, apart from a unique name describing the service, also information on what
protocol (TCP, UDP or both) and what source and destination ports are applicable for the service.
Specifying Port Numbers
Port numbers can be specified in a number of ways. These are:
Single Port
Value
----------------
Name: echo
7
Type: TCPUDP (TCP/UDP)
0-65535
No
ALG: (none)
1000
Echo service
For many services, a single destination port is sufficient.
HTTP, for instance, uses destination port 80 in most cases.
SMTP uses port 25 and so on. For these types of Service, the
single port number is simply specified in the TCP/UDP
Service object.
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Chapter 3. Fundamentals