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

3.2.2. TCP and UDP Based Services

DestinationPorts:
SourcePorts:
PassICMPReturn:
MaxSessions:
Comments:
Web Interface
1. Go to Objects > Services
2. Select the specific service object in the grid control.
3. A grid 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, in-
cludes mechanisms for reliable transmission of data. TCP is used by many common applications,
such as HTTP, FTP and SMTP, where error-free transfers are mandatory.
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 over-
head 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 mechan-
isms.
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.
Port numbers can be specified in several ways:
Single Port
Port Ranges
Multiple Ports and Port Ranges
Name: echo
7
Type: TCPUDP (TCP/UDP)
0-65535
No
ALG: (none)
1000
Echo service
For many services, a single destination port is sufficient. HT-
TP, for instance, uses destination port 80 in most cases,
SMTP uses port 25 and so forth. For this type of services, the
single port number is simply specified in the TCP/UDP Ser-
vice object.
Some services use a range of destination ports. As an ex-
ample, the NetBIOS protocol used by Microsoft Windows
uses destination ports 137 to 139. To define a range of ports
in a TCP/UDP Service object, the format mmm-nnn is used.
A port range is inclusive, meaning that a range specified as
137-139 covers ports 137, 138 and 139.
Multiple ranges or individual ports may also be entered, sep-
arated by commas. This provides the possibility to cover a
wide range of ports using only a single TCP/UDP Service ob-
ject. For instance, all Microsoft Windows networking can be
covered using a port definition specified as 135-139,445. HT-
TP and Secure HTTP (HTTPS) can be covered by stating des-
tination ports 80,443.
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Chapter 3. Fundamentals