TCP/IP Basics - CITE

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26 Οκτ 2013 (πριν από 3 χρόνια και 7 μήνες)

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TCP/IP

TCP/IP Basics

Alvin Kwan


TCP/IP

What is TCP/IP?


It is a protocol suite governing how data can
be communicated in a network environment,
both local and globally.


To remind you what a protocol is, please read
http://www.leapforum.org/published/internetw
orkMobility/split/node10.html

to learn a
particular protocol known as ARQ (automatic
repeat request) protocol


TCP/IP

OSI vs. TCP/IP

TCP/IP

History of TCP/IP (1/2)


Stands for
Transmission Control
Protocol/Internet Protocol

(TCP/IP)


Developed by Defense Advanced Research
Projects Agency (DARPA) under the
sponsorship of U.S. Department of Defense
(DoD) in since late 1960s


1972


Telnet


1973


File Transfer Protocol

(FTP)


1974


Transmission Control Protocol

(TCP)

TCP/IP

History of TCP/IP (2/2)


1980


User Datagram Protocol

(TCP)


1981


Internet Protocol

(TCP)


1982


TCP/IP as a protocol suite


1984


Domain Name System

(DNS)


1991


Transfer of funding responsibility from
DAPRA to
National Science Foundation

(NSF), which started to turn the military
originated protocols into civic use, notably in
education sector

TCP/IP

Some TCP/IP features


It is an open standard, which is also adopted
by the Internet.


It offers a routable protocol such that the path
of every piece of data that moves through the
network is traceable.


It adopts a single and simple addressing
scheme which is easy to understand


IP is a
connectionless

protocol (with data
transferred in individual packets); whereas
TCP is connection
-
oriented.

TCP/IP

Connectionless vs.

Connection
-
oriented Protocols (1/2)


Connectionless protocols


The

data

communication

method

occurs

between

hosts

with

no

previous

setup


Send data across the network to its destination without
guaranteeing receipt


Higher layers handle packet sequencing and certain
data integrity control issues


Fast; require little overhead


Most LAN protocols at the data link layer are
connectionless


Data packets in a connectionless communication are
referred to as
datagrams

More to follow …

TCP/IP

Connectionless vs.

Connection
-
oriented Protocols (2/2)


Connection
-
oriented protocols


Establish a formal connection between two
computers, guaranteeing the data will reach its
destination


Higher layers can rely on low layers to handle
matters of packet sequencing, data integrity, and
delivery timeouts


Slower but more reliable


ATM networks are connection oriented at the
data link layer

TCP/IP

Network Interface Layer (1/3)


Lowest layer in the TCP/IP stack


To define how a computer connects to a
network


It does not regulate the type of network that
the host is on and thus TCP/IP can be run on
an Ethernet, Token Ring or Fiber Distributed
Data Interface (FDDI) or any other network
topology

TCP/IP

Network Interface Layer (2/3)


Physical (or MAC) address, which is burnt
into every network interface card (NIC)


MAC address is usually represented in 12
hexadecimal digits (or 48 bits)


First six hexadecimal digits uniquely represent
the manufacturer


Last six hexadecimal digits is a unique serial
number that the card’s manufacturer has
assigned to the NIC

TCP/IP

Network Interface Layer (3/3)


For a TCP/IP packet to be delivered, it must
contain the destination node’s MAC address so
that a host can check whether the packet is
directed to it.


A
broadcast packet

is designed to be attended
by all hosts and it has a target MAC address of
FFFFFFFF, i.e., all bits set.

TCP/IP

The Internet Layer


The internal layer contains protocols for
addressing and routing of packets.


Internet Protocol (IP)


Address Resolution Protocol (ARP)


Internet Control Message Protocol (ICMP)


Internet Group Message Protocol (IGMP)


Routing protocols (e.g., RIP)

TCP/IP

Internet Protocol (1/2)


To determine the source and destination IP
addresses of every packet


Every host on a network is assigned a unique
IP address (logical address)


IP address is divided into two parts: network
number and host address on that network


Based on the subnet mask and IP address, it
can be decided whether the target is a
“remote” host or a “local” host (and details will
be given later)

TCP/IP

Internet Protocol (2/2)


For a remote host, IP needs to send the
packet through a gateway or a router (which
is also identified by an IP address).


Connectionless and thus unreliable
transmissiion

TCP/IP

Address Resolution Protocol
(ARP)


Protocol to resolve an IP address to a physical
address.


The hardware address will be cached for a short
time.


To resolve an IP address to a physical address


Try the ARP cache (kept in RAM)


If not found in cache, initiate an ARP request
broadcast and keep the result in cache


Try the command “ARP

A” in a command
window

TCP/IP

ARP Command

TCP/IP

Internet Control Message Protocol
(ICMP)


For sending error messages, performing
diagnostics and controlling data flow


Try “ping cite.hku.hk” to test the network
connection to another host

TCP/IP

Internet Group Message Protocol
(IGMP)


IGMP enables one host to send one stream of
data to many hosts at the same time with the
use of a multicast address


Some routing protocols use IGMP to
exchange routing tables

TCP/IP

Routing Protocols


Routing Information Protocol (RIP)


Simple IP
-
based routing protocol that collects
and exchange information about network route
and status


Only suitable for small networks


Open Shortest Path First (OSPF)


Typically used by routers to determine the best
path through a network

TCP/IP

Transport Layer


Transmission Control Protocol (TCP)


Primary IP transport protocol


Connection
-
oriented and thus guarantee a more
reliable delivery


Use port numbers to identify communicating
applications


Responsible for message fragmentation and
reassembly (with the use of sequence number)


User Datagram Protocol (UDP)


A connectionless transport protocol which runs faster

continued

TCP/IP

TCP/IP Applications


Domain Name System (DNS)


For URL to IP
-
address translation


File Transfer Protocol (FTP)


Application protocol for file transfer and directory/file
manipulation services


Telnet


For remote terminal sign
-
on


Simple Mail Transport Protocol (SMTP)


Provide messaging services (i.e., sending e
-
mails)

continued

TCP/IP

IP Addressing


IP is responsible for addressing and routing in the
TCP/IP environment


IP addresses


Logical addresses, which are 32 bits (4 bytes) long


A decimal number from 0 to 255, separated by periods,
represents each byte or octet


Two sections


One defines the network a computer is on


One defines the host ID for a computer


Example: 172.24.206.18

TCP/IP

IP Addressing


Originally, three classes of IP addresses


Class A


Large corporations


ID numbers between 1 and 126 (in its first octet, or 8 bits)


Class B


Medium
-
sized networks


Network IDs between 128 and 191 (in its first octet, or 8 bits)


Class C


Small networks


Range from 192 to 223 (in its first octet, or 8 bits)


IP address registries manage the total collection of valid
IP addresses

TCP/IP

IP Addressing


IP addresses are rapidly becoming scarce


TCP/IP’s technical governing body has
reserved a series of addresses for private
networks


IETF is working on a new implementation of
TCP/IP (IPv6) that uses addresses that are 8
bytes long but retain backward compatibility
with IPv4 4
-
byte addresses

TCP/IP

Classless Inter
-
domain Routing
(CIDR) (1/2)


A more efficient way to assign IP addresses than
using IP address “classes”


The network and host addresses boundary is not
always made on octet boundaries, but may be
made any specific number of bits from the
beginning of the address


Steal bits from the network address for use in the
host address and this is also called
supernetting


A slash following IP address is used to indicate
the number of bits of the network address, e.g.,
192.203.187.32 /22

TCP/IP

Classless Inter
-
domain Routing
(CIDR ) (2/2)


Advantages


Subnet ID may now be all 0’s or 1’s


Avoid of wasting a number of IP addresses
when subnetting a Class C address


Disadvantages


Router support is needed


All possible bit patterns used for supernetting
a network are to be reserved to be used by
that network only

TCP/IP

Subnet Masks


The “all ones” bit pattern that masks the
network portion of an IP address


Class A address default: 255.0.0.0


Class B address default: 255.255.0.0


Class C address default: 255.255.255.0

TCP/IP

Examples on Subnet Mask and
Supernets


See pp203
-
205 of the recommended reading

TCP/IP

Dynamic Host Configuration
Protocol (DHCP)


A TCP/IP protocol that allows automatic IP
addresses and subnet mask assignment


Major benefit is ease with which computers
can be moved


Not suitable for systems that require a static
address, such as web servers


A dedicated host, which can be a router or a
computer, to take the role of DHCP server

TCP/IP

Readings


http://www.wown.com/j_helmig/tcpip.htm


http://www.yale.edu/pclt/COMM/TCPIP.HTM


http://www.ii.uib.no/~magnus/TCP
-
1.html
http://www.pcsupportadvisor.com/search/c04100.htm