UDP provides a connectionless, unreliable transport service. It is often used for one-to-many communications, using broadcast or multicast IP datagrams. As delivery of UDP datagrams is not guaranteed, applications using UDP must supply their own mechanisms for reliability if needed. Microsoft networking uses UDP for logon, browsing, and name resolution.
UDP and Name Resolution
UDP is used for NetBIOS name resolution via unicast
to a NetBIOS name server or subnet broadcasts, and for DNS (Domain Name
System) hostname/IP address resolution. NetBIOS name resolution is accomplished
over UDP port 137. DNS queries use UDP port 53. Since UDP itself does not
guarantee delivery of datagrams, both of these services use their own re-transmission
schemes if they receive no answer to queries. Broadcast UDP datagrams are
not usually forwarded over IP routers, so NetBIOS name resolution in a
routed environment requires a nameserver of some type, or the use of static
database files.
Mailslots over UDP
Mailslot messaging is used by many NetBIOS applications.
A 2nd class mailslot is a simple mechanism for sending a message from one
NetBIOS name to another over UDP. Mailslot messages may be broadcast on
a subnet, or may be directed to the remote system. In order to direct a
mailslot message to another system, there must be some method of NetBIOS
name resolution available. Microsoft provides WINS (Windows Internet Name
Server) for this purpose
UNC Universal (Uniform)Name Convention
Short for Universal Naming Convention or Uniform Naming Convention, a PC format for specifying the location of resources on a local-area network (LAN). UNC uses the following format:
\\server-name\shared-resource-pathname
So, for example, to access the file test.txt in the directory examples on the shared server silo, you would write:
\\silo\examples\test.txt
You can also use UNC to identify shared peripheral devices, such as
printers. The idea behind UNC is to provide a format so that each shared
resource can be identified with a unique address.