Title: Chapter 4 Internet Addressing and Operation
1Chapter 4 Internet Addressing and Operation
- Part 1 Data Communications in the Information Age
2Topics Addressed in Chapter 4
- Internal Addressing
- Internet naming conventions
- Subnet masks
- Static vs. dynamic IP addresses
- IP routing
- Internet tools for network managers
- Web page design tools
- Server configurations
- TCP/IP and security
3Converting to Binary
4Internet Addresses
- IPv4 is currently the standard for IP addressing
- IPv4 addressing is described in RFC 760
- 32-bit addresses are specified
- IPv6 addresses are 128-bits in length
- IPv6 is used in Internet2 and will be more widely
used in the future on the Internet - IP addressing is primarily concerned with
establishing a unique identity for networked
computers - By doing this, IP addressing enables packets to
be routed between networks and delivered to the
appropriate host or node on the destination
network
5IP Addressing Basics
- IPv4 addresses are usually written as four
separate numbers delineated by a period - For example 101.209.33.17
- This way of representing an IP address is called
the dotted-quad notation - Each number in the four-number group is
represented as an 8-bit octet in an IPv4 header - For example 101.209.33.17 would be represented
as - 01100101 11010001 00100001 00010001
6More IP Addressing Basics
- In IPv4, each 32-bit IP address is subdivided
into network and host/node portions - This is illustrated in Figure 4-2
- The composition of the first four bits in the IP
address specifies whether the network portion is
1, 2, or 3 bytes in length - These four bits determine whether the host/node
has a Class A, B, C, D, E address (see Table 4-1)
7Figure 4-2
8IPv4 Address ClassesTable 4-1
9IPv4 ClassesTable 4-2
10Reserved IP Addresses
- The developers of the IPv4 addressing scheme
reserved three blocks of addresses for networks
that would not be connected to the Internet - These are identified and defined in RFC 1918
- Reserved address ranges are illustrated in Table
4-3
11Table 4-3
12Domain Names
- For most Internet users, dotted-quad
representations for Internet hosts/nodes are
cumbersome. As a result, most users rely on
domain name conventions instead - Domain names are included in URLs
- A domain name is a word-orientated representation
of an Internet address - ICANN is responsible for approving domain names,
including abbreviations used in URLs
13Domain Name Conventions
- The address elements of a domain name are ordered
from most to least specific - For example, in frodo.mycompany.com.us
- frodo probably represents the name of an Internet
host owned by the company mycompany - The com identifies the mycompany entity as a
company and us identifies the country in which
the hosts network is located - The hierarchical nature of domain names is
illustrated in Figure 4-3
14The Hierarchical Nature of Domain NamesFigure 4-3
15Domain Names and URLs
- When a domain name is included in a URL, it must
be resolved to an IP address - This is done by the Internets Domain Name System
(DNS) - Domain names and their IP addresses are stored in
databases on domain name servers - When a domain name must be resolved, a message is
sent to the closest domain name server to obtain
the IP address. If that server does not know the
IP address, it sends a request to other domain
servers for the information - Once the IP address for a domain name is known,
the host/node inserts the IP address as the
destination address for the packet so that it can
be routed to appropriate recipient
16URL Protocols
- HTTP is not the only TCP/IP protocol that uses
URLs - Others are identified in Table 4-7
- Although these differ slightly in format (see
Table 4-8), all use domain names and therefore
rely on the Domain Name System in order to operate
17Table 4-7
18Table 4-8
19Subnet Addressing
- Because there is a limited number of available
IPv4 addresses, IPv4 developers provided
mechanisms for sharing a single network address
among two or more subnets - These mechanisms are described in RFC 950
- RFC 950 enables class A, B, and C networks to be
split into smaller networks that use the same
network assignment numbers
20Subnetting Advantages
- Subnetting has the following advantages
- It simplifies network administration each
network segment can be maintained independently
and efficiently - Intranets can be restructured without affecting
the overall networks interfaces with the
Internet and other external networks - Because intranet subnetting is not visible to
external networks it can be used to enhance the
overall security of the organizations networks
21Subnetting Basics
- Subnetting enables network managers to extend the
network portion of IPv4 addresses by taking away
a portion of the host/node portion of the IP
address - The portion that is taken away is used as a
subnet identifier - This is illustrated in Figure 4-4
22Figure 4-4
23Subnet Masks
- A subnet mask is a binary bit pattern that is
stored in hosts, nodes, and routers - It is matched up with an incoming packets
destination IP address to determine whether to
accept or reject the packet - Every TCP/IP network host/node or router stores a
subnet mask along with its IP address (see Figure
4-6) - The subnet mask specifies which bits in an IP
address should be treated as an extended network
address (network subnet) and which bits
represent the host/node portion of the address - Default subnet masks exists for class A, B, and C
networks (see Table 4-9) - Table 4-10 summarizes alternative class C subnet
masks - Figure 4-5 illustrates how a subnet mask is used
to decompose an IPv4 address into its subnet and
host/node addresses
24Figure 4-6
25Table 4-9
Table 4-10
26Figure 4-5
27Static vs. Dynamic IP Addresses
- Host/node addresses can be allocated in one of
two ways - Static assignments
- Dynamic assignments
- Static IP addresses are permanently assigned to
hosts and node - Servers and routers are typically assigned static
IP addresses - These can be assigned to hosts/nodes through
manual configuration or by always assigning the
same IP address to a particular host/node when it
comes online - Dynamic IP addresses are automatically assigned
to client stations in a TCP/IP network when they
come online - DHCP servers assign dynamic IP addresses to
clients
28Dynamic Host Configuration Protocol (DHCP)
- The most common approach for dynamically
assigning IP addresses is DHCP (Dynamic Host
Configuration Protocol) - Each DHCP server has a range of IP addresses that
can be assigned and maintains a list of currently
assigned and currently unassigned IP addresses - DHCP client software enables a network host/node
to request an IP address from a DHCP server when
it comes online - This process is illustrated in Figure 4-9
- When the client goes offline, it notifies the
DHCP server that it is releasing the IP address.
Once released, the IP address is placed on the
DHCP servers assignable address list
29Figure 4-9
30Internet Addressing in LANs
- Additional addressing processes take place when
the host/node that needs to connect to the
Internet is in a LAN - In LANs, physical (MAC) addresses (the address of
the computers network interface cards) are used
for message delivery - When a LAN host/node has both an IP address and a
MAC address, an incoming IP packet can only be
delivered to the computer after the IP address
has been translated to a MAC address - The protocol that performs this function is
address resolution protocol (ARP)
31Address Resolution Protocol (ARP)
- ARP servers maintain tables that contain
host/node IP addresses and corresponding MAC
addresses (see Table 4-12) - If the destination nodes IP address is in the
ARP table, it extracts the corresponding MAC
address and uses it to build the MAC header
needed to send the message to the node - ARP is found at the Internet layer of the TCP/IP
protocol stack (see Figure 4-10) but is often
described as overlapping the Internet and media
access layers because of its role in translating
IP to MAC addresses
32Table 4-12
33Figure 4-10
34IP Routing
- Routers leverage routing tables when determining
how to route a packet to the destination nodes
IP address - Some of the information found in routing tables
is found in Table 4-13 - Essentially, when a router receives a packet, it
- identifies the destination nodes IP address in
the packet header - consults the routing table to determine the best
path to the destination nodes network across the
Internet backbone - Addresses the packet to the next router on the
best path and transmits the packet out the
appropriate port - This process is illustrated in Figure 4-12
35Figure 4-12
36Ports and Sockets
- Once received by the destination host/node, a
packet progresses up the layers of the TCP/IP
protocol stack and is directed to the appropriate
application - Port numbers are included in TCP or UDP headers
to identify the application layer protocol that
generated the data in the packet - Some port numbers are permanently assigned to
applications/services (see Table 4-15) - The combination of an IP address and a port
number is called a socket - For example, the socket notation for a Web page
request on a Web server whose IP address is
141.165.231.193 would be 141.165.231.19380
37Examples of Well-Known PortsTable 4-15
38Internet Tools for Network Managers
- Some of the Internet tools used by network
managers include - Finger (see Table 4-16)
- Ping (see Figure 4-13)
- Tracert (see Figure 4-14)
- WHOIS database
39Internet ToolsTable 4-16 Figure 4-13
40Figure 4-14
41Web Page Design Tools
- Some of the major Web page design tools include
- Hypertext Markup Language (HTML)
- Dynamic HTML (DHTML)
- Extensible Markup Language (XML)
- see Table 4-17 and Figure 4-16
- Vector Markup Language (VML)
- Precision Graphics Markup Language (PGML)
- Virtual Reality Markup Language (VRML)
- These all evolved from SGML (see Figure 4-15)
- GIF, JPEG, and PNG are examples of graphics files
used by Web page designers (see Table 4-18)
42Server Configurations
- At large commercial Web sites, a group of servers
may share a single URL. This collective host is
called a server farm - Server farms help ensure reliable access and
fault tolerance - Load balancing involves the use of a switch or
router to transfer user requests to particular
servers in a server farm (see Figure 4-17) - In a server cluster, a group of servers acts as a
single team and is responsible for allocating the
total workload that they are responsible for
handling
43Figure 4-17
44TCP/IP and Security
- Important TCP/IP security technologies include
- Proxy servers that stand between the Internet and
a private network and help prevent outsiders from
accessing internal addresses and other network
details (see Figure 4-18) - Network address translation (NAT) is an important
proxy server capability - Virtual private networks (VPNs) that use
tunneling protocols, authentication, and
encryption to establish private links for a
corporate network across the Internet and other
public networks - IPSEC (Internet Protocol Security Architecture)
that provides secure data transmission across IP
networks via authentication and encryption (see
Figure 4-19)
45Figure 4-18
46Figure 4-19
47IPSEC Uses
- Because IPSEC enables secure communications
across public TCP/IP networks such as the
Internet, it is used to - Build secure VPNs among branch offices
- Implement secure remote access for teleworkers
- Create secure extranets with business partners
- Provide security for B2B e-commerce, e-mail, file
transfers, remote logons, and other distributed
applications
48Chapter 4 Internet Addressing and Operation
- Part 1 Data Communications in the Information Age