Although Windows 7 has the capability of using several
networking protocols, the primary protocols used are TCP and IP. Windows 7
uses the TCP/IP protocol for networking among peer-to-peer networks,
domain-controlled networks, and the Internet. TCP/IP is a vital protocol
set for using your operating system fully.Windows 7 contains a new TCP/IP stack, referred to as a dual stack,
that works with IP version 4 (IPv4) and IP version 6 (IPv6). IPv4 uses a
limited 32-bit address space, defined by four octets and a subnet mask
composed of four octets. IPv6 uses a 128-bit addressing scheme, allowing
for the needed IP growth of the Internet.
1. Understanding IPv4
IP addresses used with IPv4 can be divided into two parts:
the network ID and the host ID. The network ID identifies the network on
which a computer or device is located and the host ID identifies the
computer or device.
An example of an IPv4 address is 192.168.1.1, which shows the four
distinct sets of numbers divided by a period, or dot. Each section
separated by a dot is referred to as an octet,
which correlates to an eight-bit number in binary form.
The second set of numbers associated with an IPv4 address is the
subnet mask. The subnet mask identifies which parts of the IP address
belong to the network ID and which parts belong to the host ID.
Subnet masks use four distinct octets separated by a period, or
dot, just like the IP address. Subnet masking correlates to the network
ID and the actual host ID of the computer by giving binary values of
either a 1, for a bit that belongs to the network ID, or 0, for a bit
that belongs to the host ID. An example of a subnet mask is 255.0.0.0,
which is read in binary as 11111111.00000000.00000000.00000000. Thus,
the first 8 bits of the IP address belong to the network ID and the
final 24 bits belong to the host ID.
When you use standard subnet masks, you are said to be using a
classful network.
Classful networks are defined in three different classes: Class A, Class
B, and Class C. Table 1 shows examples of
the different classful networks. Table 2
shows network ID examples, and Table 3 gives some examples of
subnet forms translated into binary to help you understand the
differences in their formats and to differentiate the network ID portion
of the subnet from the host ID portion of the subnet.
Table 1. IPv4 subnet example
| Subnet
class | Example | Maximum
nodes |
|---|
| Class A | 255.0.0.0 | 16,777,214 |
| Class B | 255.255.0.0 | 65,534 |
| Class C | 255.255.255.0 | 254 |
Table 2. IPv4 network example
| Network
ID | Subnet
mask | Host IP
range | Broadcast
address |
|---|
| 10.0.0.0 | 255.0.0.0 | 10.0.0.1–10.255.255.254 | 10.255.255.255 |
| 169.254.0.0 | 255.255.0.0 | 169.254.0.1–169.254.255.254 | 169.254.255.255 |
| 192.168.1.0 | 255.255.255.0 | 192.168.1.1–192.168.1.254 | 192.168.1.255 |
Table 3. IPv4 subnet to binary form example
| Decimal subnet
form | Binary subnet
form |
|---|
| 255.0.0.0 | 11111111.00000000.00000000.00000000 |
| 255.255.0.0 | 11111111.11111111.00000000.00000000 |
| 255.255.255.0 | 11111111.11111111.11111111.00000000 |
For every network, two host addresses are reserved: the network
address and the broadcast address. The network address is used to
identify the unique network. The broadcast address is used to broadcast
a message to all hosts on a network. On a classful network, address 0 is
reserved to indicate the network number, and address 255 is reserved for
the broadcast address.
Class A networks use the first octet in the range of 1–126. The
remaining three octets define unique host IDs. Each Class A network may
contain up to 16,777,214 nodes.
Class B networks use the first two octets in the range of 128–191.
The remaining two octets define the unique host IDs. Each Class B
network may contain up to 65,534 nodes.
Class C networks use the first three octets in the range of
192–223. The remaining octet is for unique host IDs. Each Class C
network may contain up to 254 hosts.
NOTE
Out of these IP address ranges, you may note that some ranges
are missing. The 127 network is reserved for local loopback. Your
computer typically uses the address 127.0.0.1 to send messages to
itself. The network addresses from 224 to 239 are used for multicast
IPv4 addresses.
When you are working with IPv4, data is sent in discrete packets
of information with a header and a payload. IPv4 headers are variable in
size, between 20 and 60 bytes, in 4-byte increments. Each bit range is
broken into different sections, which correspond to the range of a
related field in a packet. Bit ranges consist of 0–3, 4–7, 8–15, 16–18,
and 19–31. These correspond to the values 0, 32, 64, 96, 128, 160, and
160/192+ for data. See Table 4 for
examples of the ranges and their use. The IP payload is of variable size
as well, ranging from 8 bytes to 65,515 bytes (with sizing primarily
depending on network protocols and other options). Although most people
will never use this information on a regular basis, it is very useful
for understanding how to troubleshoot network problems.
Table 4. IPv4 packet information
| + | Bits
0–3 | 4–7 | 8–15 | 16–18 | 19–31 |
|---|
| 0 | Version | Header
length | Type of
service | Total
length |
|
| 32 | Identification |
|
| Flags | Fragment offset |
| 64 | Time to Live
(TTL) |
| Protocol | Header
checksum |
|
| 96 | Source address
information |
|
|
|
|
| 128 | Destination address
information |
|
|
|
|
| 160 | Optional
information |
|
|
|
|
| 160/192+ | Data
transmitted |
|
|
|
|
2. Using Private IPv4 Addresses and Networking Protocols
Some IP addresses designated for Class A, B, and C
networks are defined as public and others are defined as private.
Public IP addresses are assigned by ISPs. ISPs obtain
their IP addresses from a regional Internet registry. When you connect
directly to the Internet through dial-up or by connecting an ISP’s
cable/DSL modem directly to your computer, your computer uses a public
IP address assigned by your ISP. Not every computer that connects to the
Internet needs its own IP address, however. If it did, the IPv4
addressing scheme would have run out of new addresses a long time ago.
This is where private IP addresses come into the picture.
When you set up a network, you assign the computers on the network
private IP addresses. Private IP addresses are defined as follows:
Class A private IP addresses include the addresses from
10.0.0.0 through 10.255.255.255.
Class B private IP addresses include the addresses from
172.16.0.0 through 172.31.255.255.
Class C private IP addresses include the addresses from
192.168.0.0 through 192.168.255.255.
Because private IP addresses are not routable to the Internet,
your network can use the same private IP addresses that other people are
using with their networks. When a computer is connected to a network
that in turn connects to an ISP, your broadband router is the device
that is assigned a public IP address. Your broadband router uses some
tricks to allow computers with private addresses to access the Internet,
despite the fact that private addresses are not routable to the
Internet. Generally speaking, the router’s public IP address is the
address by which all the computers on your network will be identified
when they are accessing resources on the Internet.
On a network, private IP addresses are assigned in one of three
ways:
- Static IP address
A fixed IP address that you manually assign to a
computer or device.
- Dynamic IP address
An IP address automatically assigned to a computer
or device by DHCP.
- Automatic private IP address
An IP address automatically assigned to a computer
by the operating system when a DHCP server cannot be contacted.
Sometimes referred to as link-local
addresses.
On a home or small-office network, you can use the DHCP service
capability of your Ethernet router to assign IP addresses. Refer to the
user manual of your router to find the correct procedure to configure
the DHCP service to assign IP addresses automatically to computers and
devices connecting to your network. Once you’ve configured the DHCP
service, you may need to configure the network adapters of computers and
devices to use DHCP, although it is typically the default IP addressing
scheme.
