Chapter 6 - Jedvorak.com

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Oct 27, 2013 (4 years and 2 months ago)

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Chapter 6

Networking Protocols


Introduction


Look at:


Protocol Basics(6.1)


A Brief Protocol Prospectus(6.2)


Transmission Control Protocol/Internet
Protocol (TCP/IP)(6.3)


TCP/IP Network Access Layer
Protocols(6.4)


Introduction


Look at:


TCP/IP Internet Layer Protocols(6.5)


TCP/IP Transport Layer Protocols(6.6)


TCP/IP Application Layer Protocols(6.7)

Protocol Basics


A protocol is a set of rules and conventions
that determines how computers exchange
information over a network medium


A wide variety of communication protocols
exist, and many of them rely on others for
operation


Groups of related protocols are often called
stacks

or

protocol stacks


A Brief Protocol Prospectus


Data packets can be sent over the medium
using any one of a number of protocols


Protocols can be either standard or
proprietary


A
standard protocol is one where users can
purchase equipment from any manufacturer
because it is programmed to communicate
universally

A Brief Protocol Prospectus


A proprietary protocol is usually protected by
patents or other legal stipulation


Proprietary protocols include


XNS


NetBIOS


IPX/SPX


AppleTalk


DECNet



A Brief Protocol Prospectus


XNS stands for the Xerox Network
Systems


This is a suite of protocols created by
Xerox in the late 1970s and early 1980s
for use in Ethernet networks


XNS is used in very few new networks
today

A Brief Protocol Prospectus


The Network Basic Input/Output
System (NetBIOS) interface was
developed in 1983 for IBM


The intention was to allow applications
on different computers to communicate
within a local area network


NetBIOS was not designed for large
networks

A Brief Protocol Prospectus


In the early 1980s, Novell introduced its own
network protocol stack called Internetwork
Packet Exchange/Sequenced Packet
Exchange (IPX/SPX)


This stack was based on the XNS network
protocol family


IPX is the Network layer protocol


SPX is the Transport layer protocol


A Brief Protocol Prospectus


AppleTalk is Macintosh’s networking protocol



It is designed to be a flexible, simple, and
inexpensive network means for connecting
computers, peripherals, and servers


Newer versions of Macintosh operating
systems use TCP/IP and SMB as default
protocols rather than AppleTalk


AppleTalk is a protocol and LocalTalk is a
media type

A Brief Protocol Prospectus


DECnet

is a proprietary network protocol
designed by Digital Equipment Corporation


Currently two versions of DECnet are in use:


DECnet Phase IV which is based on the
Phase IV Digital Network Architecture
(DNA)


DECnet/OSI also called DECnet Phase V
is a layered model

Transmission Control
Protocol/Internet Protocol


TCP/IP is considered the language of the
Internet


It is the most widely used protocol today


It is a suite, or stack, of small, specialized
protocols


Because of its routing ability, TCP/IP has
become the protocol of choice for many
LANs, as well as the basis for the Internet,
making it the standard

Transmission Control
Protocol/Internet Protocol


In the early 1970s, the Department of
Defense funded ARPA to design a new set of
computer communication protocols that
would allow multiple networks to be
interconnected in a flexible and dynamic way


The protocol developed was originally called
Network Control Protocol


This success led to the implementation of the
two main Internet protocols


These are Transmission Control Protocol and
Internet Protocol (TCP/IP)

Transmission Control
Protocol/Internet Protocol


TCP/IP’s implementation of the OSI
model makes functionality simpler


It maps the same seven layers of
the OSI model to a four
-
layer
TCP/IP model instead


The TCP/IP model focuses more on
delivering interconnectivity than on
functional layers

Transmission Control
Protocol/Internet Protocol


Since TCP/IP is the language of the Internet,
you may also hear this model referred to as
the Internet reference model


The Layers are:


Network Access


Internet


Transport


Application


TCP/IP Network Access Layer
Protocols


The Network Access layer is the lowest
layer in the model


It Maps to Layers 1 (Physical) and 2
(Data Link) of the OSI model


It is responsible for the delivery of
datagrams by creating a frame for the
network type and then sending the data
to the wire

TCP/IP Network Access Layer
Protocols


This layer contains the protocols that are
used to deliver data to computers and
devices on the network


These include Serial Line Interface Protocol
(SLIP) and Point
-
to
-
Point Protocol (PPP)


These are communication protocols for serial
data transmission by which IP packets can be
sent over a modem

TCP/IP Network Access Layer
Protocols


Other protocols that are used at this layer
include a means to relate different types of
addresses to each other:


the Address Resolution Protocol (ARP)


the Reverse Address Resolution Protocol
(RARP)


This layer defines the logical network layout
so routers can determine where to forward
packets

TCP/IP Internet Layer Protocols


The layer above the Network Access
layer is called the Internet layer


It manages the routing of packets that
are to be forwarded on to different
networks


It relies on routable protocols for
delivery

TCP/IP Internet Layer Protocols


The Internet Protocol (IP) is responsible for
making data packets routable


It is a forwarding protocol that uses routing
tables that are created by routing protocols


It is a simple, connectionless internetworking
protocol



The basis of IP is how it uses routing tables to
make decisions about routing an IP packet

TCP/IP Internet Layer Protocols


Every host on the network needs
an IP address


TCP/IP uses a 32
-
bit Layer 3 address in
the format xxx.xxx.xxx.xxx to identify the
network and the host compute


Each set of xxx is called an octet

TCP/IP Internet Layer Protocols


There are five classes of IP addresses
their corresponding numbers are:


Class A
: Has a first octet number between
1 and 126 and can support a network with
16,777,216 hosts.


Class B
: Has a first octet number between
128 and 191 and can support 65,536 hosts



TCP/IP Internet Layer Protocols


There are five classes of IP addresses
their corresponding numbers are:


Class C
: Has a first octet number between
192 and 223 and can support 254 hosts
per network


Class D
: Begins at 224 and ends at 239.
This address class is reserved for sending
multicast messages


TCP/IP Internet Layer Protocols


A There are five classes of IP
addresses their corresponding numbers
are:


Class E
: Begins with 240 and ends at 255.
This address class is reserved for
experimental use


The IP address 127.0.0.1 is used as the
loopback address

TCP/IP Internet Layer Protocols


A datagram

is the packet format defined by IP


Datagrams are packets that consist of a
header, data, and a trailer


The header contains information that the
network needs to route the datagram


Trailers typically contain a checksum value,
which is used to ensure that the data is not
modified in transit

TCP/IP Internet Layer Protocols


IP delivers the datagram by checking
the destination address in the header



When IP checks the destination address
in the header, if it is the address of a
host on the local network, the datagram
is delivered directly to the destination


If it is not on the local network, the
datagram is passed on for delivery

TCP/IP Internet Layer Protocols


Each router that a datagram passes through
is considered a hop


A system transmits IP datagrams as fast as it
can generate them


IP has two features that can affect throughput


the IP Time to Live (TTL)


IP Fragmentation


TCP/IP Internet Layer Protocols


By interconnecting multiple switches with
redundant paths, you overcome problems
with faulty cables or port failures


Another less well
-
known side effect of a loop
is the corruption of the forwarding tables on
all the switches


It would take very little time before Layer 2
broadcast loops completely destroy the
functionality of a network


TCP/IP Internet Layer Protocols


The Spanning Tree Protocol (STP) prevents
bridging loops by identifying a preferred path
through a series of looped bridges


Administrators can provide redundancy and
fault
-
tolerance by wiring a loop, and then
using STP turn off ports that would cause
loops to occur


If a primary link fails, STP will reactivate the
back
-
up port allowing normal operation of the
network to continue

TCP/IP Internet Layer Protocols


The TTL field is actually the number of
hops the datagram has made


IP places a limit on how long a
datagram may live in the network


Specifications for higher
-
layer protocols
usually assume that the maximum time
a datagram can live in the network is
only two minutes

TCP/IP Internet Layer Protocols


Each type of network has a maximum
transmission unit (MTU), which is the largest
packet it can transfer


A datagram received from one network may
be too large to be transmitted in a single
packet on another network


It may be necessary to divide the datagram
into smaller pieces


This division process is called fragmentation

TCP/IP Internet Layer Protocols


Internet Control Message Protocol (ICMP) is
part of the Internet layer and uses IP
datagram delivery to send its messages


ICMP uses the basic support of IP as if it was
higher
-
level protocol, but it is actually an
integrated part of IP


ICMP is a protocol meant to be used as an
aid for other protocols


It is used to test for connectivity and search
for configuration errors in a network

TCP/IP Internet Layer Protocols


PING uses the ICMP echo function


A small packet containing an ICMP

echo
message is sent through the network to a
particular IP address


The computer that sent the packet then waits
for a return packet


If the connections are good and the target
computer is up, the echo message return
packet will be received

TCP/IP Internet Layer Protocols


PING is one of the most useful network tools
available because it tests the most basic
function of an IP network


Traceroute

was originally developed for the
Unix operating system but is used for many
operating systems and most routers


It is used to track the path a packet takes to
get to its destination


It measures how long it takes to travel
through each hop to get to its target

TCP/IP Internet Layer Protocols


Traceroute uses an ICMP echo request
packet to find the path


Besides assisting in troubleshooting
functions such as PING and Traceroute,
ICMP capabilities include:


Announcing network errors


Congestion


Timeout notification

TCP/IP Transport Layer
Protocols



The protocol layer above the Internet
layer is the Transport

layer


It is responsible for providing end
-
to
-
end
data integrity


It also provides a reliable
communication service so that an
extended two
-
way conversation may
take place

TCP/IP Transport Layer
Protocols


This layer accepts and returns
information to be transmitted as a
stream of characters


It uses open and close commands to
initiate and terminate the connection


It consists of two protocols:


Transmission Control Protocol (TCP)


User Datagram Protocol (UDP)

TCP/IP Transport Layer
Protocols


TCP provides connection
-
oriented data
transmission


It can support multiple data streams


It provides for flow and error control


It uses sequence numbers and
acknowledgements to guarantee
delivery

TCP/IP Transport Layer
Protocols


Sockets make up a TCP connection


The two most typical network
applications that use TCP are:



File Transfer Protocol (FTP)



Telnet


Telnet uses port 23


FTP uses port 21

TCP/IP Transport Layer
Protocols


UDP does not provide either
sequencing or acknowledgements


It is a connectionless protocol


It is used a lot in telephony traffic and
the Remote Procedure Call (RPC)


The major difference between TCP and
UDP is reliability

TCP/IP Application Layer
Protocols



The top layer in the Internet reference
model is the Application layer


This is how applications and certain
services access the network


It provides the services that applications
use to communicate over the network


It serves as a service provider for
workstations and applications.

TCP/IP Application Layer
Protocols


The most widely known and
implemented TCP/IP Application layer
services are:


File Transfer Protocol (FTP) which allows
files to be uploaded and downloaded on
port 21


Telnet which uses terminal emulation for
access to remote hosts using port 23

TCP/IP Application Layer
Protocols


The most widely known and
implemented TCP/IP Application layer
services are:


Simple Mail Transfer Protocol (SMTP)
which supports basic message delivery
services between mail servers on port 25


HyperText Transfer Protocol (HTTP) which
is a low
-
overhead Web browser service
protocol that uses port 80

TCP/IP Application Layer
Protocols


The most widely known and
implemented TCP/IP Application layer
services are:


Simple Network Management Protocol
(SNMP) which uses UDP port 161 to
collect information from network devices.


Network News Transfer Protocol (NNTP):
handles distribution and posting of news
articles using port 119

TCP/IP Application Layer
Protocols


The most widely known and
implemented TCP/IP Application
layer services are:


Dynamic Host Configuration Protocol
(DHCP) allows for automatic IP addressing


Domain Name Service (DNS) uses UDP
port 53 for resolving domain names to IP
addresses