NetBIOS
Name Resolution Process
By
default, NetBIOS names do not function over a TCP/IP network.
Windows 2003 enables NetBIOS clients to communicate over TCP/IP by
providing the NetBT protocol. NetBT is an acronym for NetBIOS over
TCP/IP. This protocol allows NetBIOS-based applications to
communicate using TCP/IP by translating the NetBIOS name to an IP
address. If WINS is configured for use, then the procedure for
resolving NetBIOS names is as follows:
1.
Computer A enters a command, such as
net use,
by using the NetBIOS name of Computer B.
2.
Computer A checks to see if the specified name is in its NetBIOS
name cache.
3.
If not, then Computer A queries a WINS server.
4.
If the WINS server cannot locate the name, then Computer A uses a
broadcast on the network.
5.
If a broadcast does not resolve the name, then Computer A checks its
Lmhosts file.
6.
If the above NetBIOS methods do not resolve the name, then Computer
A checks the Hosts file.
7.
Finally, Computer A queries a DNS server.
Examining the Data Transfer Process
TCP/IP transmits data on the network by dividing it into smaller
portions called packets. Packets are often referred to by different
terms based on the protocol with which they are associated. The
division of data into packets is necessary because a large unit of
data takes a long time to move on the network and can clog the
network. While the large unit is being transmitted, no other
computer can transmit data. Also, if an error occurs, the entire
unit of data must be retransmitted.
In
contrast, if small packets are sent on the network, they move
quickly. Because small packets don’t clog the network, other
computers can also transmit data. If any packet becomes corrupted,
only the corrupted packet needs to be retransmitted, instead of the
entire data. When a packet is transmitted in the network interface
layer, it is referred to as a frame. A frame consists of different
components that have specific functions in
the
flow of data in the network interface layer. The data flow process
involves a number of steps, including the organization of data into
small packets at the source computer and their reassembly in the
original form at the destination computer. Each layer of the TCP/IP
protocol stack is involved in these activities at both the source
and destination computers.
Packet
Terminology
As a
packet of data moves from one layer to another in the TCP/IP stack,
each protocol adds its own header information. The packet, along
with the information added to it, is referred to by a different
technical name as it is identified with different protocols. These
names are segment, message, datagram, and frame.
Segment
A
segment is the unit of transmission in TCP. It contains a TCP
header, accompanied by application data.
Message
A
message is the unit of transmission in unreliable protocols, such as
ICMP, UDP, IGMP, and ARP. It consists of a protocol header,
accompanied by application or protocol data.
Datagram
A
datagram is the unit of transmission in IP. It consists of an IP
header, accompanied by transport layer data, and is also considered
unreliable.
Frame
A
frame is the unit of transmission in the network interface layer and
consists of a header added at the network interface layer,
accompanied by IP layer data. As the name for UDP (user datagram
protocol) suggests, it can also be referred to as a datagram.
However, UDP message is the generally accepted term. The term
segment is applied when a physical device is used to divide a
network. In the context of a packet, the term segment is often
referred to as a TCP segment.
