TCP/IP Overview

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26 Οκτ 2013 (πριν από 4 χρόνια και 2 μήνες)

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Overview of TCP/IP


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Overview of TCP/IP


System Administrators and network
administrators


Why networking
-

communication


Why TCP/IP


Provides interoperable communications between all types
of hardware and all kinds of operating systems.


What is TCP/IP


An entire suite of data communication protocols,


Transmission Control Protocol (TCP) and the Internet
Protocol (IP) are two of those protocols in the suite




Overview of TCP/IP


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TCP/IP and Internet


1969 ARPAnet


Experimental packet
-
switching network


Study robust, reliable, vendor
-
independent data
communication


Very successful


1975 ARPAnet became operation network


Development continuing


TCP/IP was developed


1983 TCP/IP protocols were adopted as Military
Standards


TCP/IP was implemented in Berkeley Unix.



ARPAnet was divided into MILNET and ARPAnet




Overview of TCP/IP


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TCP/IP and Internet


1985 NSFNet


Connected to the then existing Internet (
MILNET plus ARPAnet)


Linked together the five NSF super computer
centers


Wanted to extend the network to every
scientist


1987 new NSFNet backbone


Faster


Three
-
tiered topology: backbone, regional
networks, and local networks.

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TCP/IP and Internet


1990 ARPAnet passed out of existence


1995 NSFnet ceased its role as a primary
Internet backbone network


Today Internet is build by commercial
providers.


Infrastructure is being created by


National network provider, caller tier
-
one providers


Regional network provider


Local access and user services is provided by
Internet Service Providers (ISPs)


Network Access Points (NAPS): major
interconnection points

Overview of TCP/IP


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Internet structure: network of networks


roughly hierarchical


at center: “tier
-
1” ISPs
(e.g., UUNet, BBN/Genuity,
Sprint, AT&T), national/international coverage


treat each other as equals

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

Tier
-
1
providers
interconnect
(peer)
privately

NAP

Tier
-
1 providers
also interconnect
at public network
access points
(NAPs)

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Tier
-
1 ISP: e.g., Sprint

Sprint US backbone network

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Tier
-
1 ISP: e.g., UUNET

UUNET Backbone Connectivity

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Internet structure: network of networks


“Tier
-
2” ISPs: smaller (often regional) ISPs


Connect to one or more tier
-
1 ISPs, possibly other tier
-
2 ISPs



Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

NAP

Tier
-
2 ISP

Tier
-
2 ISP

Tier
-
2 ISP

Tier
-
2 ISP

Tier
-
2 ISP

Tier
-
2 ISP pays
tier
-
1 ISP for
connectivity to
rest of Internet



tier
-
2 ISP is
c
ustomer

of

tier
-
1 provider

Tier
-
2 ISPs
also peer
privately with
each other,
interconnect
at NAP

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Tier
-
2 ISP: e.g., Abilene (Internet2)

http://loadrunner.uits.iu.edu/weathermaps/abilene/abilene.html

Overview of TCP/IP


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Internet structure: network of networks


“Tier
-
3” ISPs and local ISPs


last hop (“access”) network (closest to end systems)



Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

NAP

Tier
-
2 ISP

Tier
-
2 ISP

Tier
-
2 ISP

Tier
-
2 ISP

Tier
-
2 ISP

local

ISP

local

ISP

local

ISP

local

ISP

local

ISP

Tier 3

ISP

local

ISP

local

ISP

local

ISP

Local and tier
-

3 ISPs are
customers

of

higher tier
ISPs

connecting
them to rest
of Internet

Overview of TCP/IP


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Internet structure: network of networks


a packet passes through many networks!



Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

NAP

Tier
-
2 ISP

Tier
-
2 ISP

Tier
-
2 ISP

Tier
-
2 ISP

Tier
-
2 ISP

local

ISP

local

ISP

local

ISP

local

ISP

local

ISP

Tier 3

ISP

local

ISP

local

ISP

local

ISP

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TCP/IP and the Internet


Internet has evolved


From a simple backbone network


Through a three
-
tiered hierarchical structure


To a huge network of interconnected, distributed
network hubs.


Doubling in size every year since 1983


est. 50 million host, 100 million+ users


One thing remained constant:


Internet is build on the TCP/IP protocol.


The growth of the Internet spurred interest in
TCP/IP


it is popular.


Other network applications, email, html, http,
Mosaic,instant messaging, games


Local area networking even not connected to Internet.


Enterprise networks intranets.


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TCP/IP Features


TCP/IP met the need at the right time.


Open protocol standards


Free


Developed independently from any specific
computer hardware or operating system


Independence from specific physical
network hardware.


Ethernet


DSL connection


Dial
-
up line


Optical network

Virtually any other kind of transmission medium.


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TCP/IP Features


Common addressing scheme


allow uniquely
address any device in the entire network.


Standardized high
-
level protocols for
consistent, widely available user services.



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Protocol Standards


What is protocol?


Formal rules of behavior.


Internet Standards are developed by Internet
Engineering Task Force (IETE) in open, public
meetings.


Requests for Comments (RFCs)


Standards (STD)


Best current practices (BCP)


Informational (FYI)


Official Internet standard is rigorous


Proposed Standard


Draft Standard


At least two interoperable implementations


Internet Standard


Extensive testing


Significant benefit to the internet community.






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Protocol Standards



Two categories


Technical Specification


defines a
protocol


Applicability Statement


defines when
the protocol is to be used.


Required


Recommended


Elective


More than 3000 RFCs.

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Internet protocol stack


application:

supporting network
applications


FTP, SMTP, HTTP


transport:

host
-
host data transfer


TCP, UDP


Internet:

defines the datagram and
handles the routing of data.


IP, routing protocols


Network Access Layer:

Consist of
routines for accessing physical
network.


PPP, Ethernet


Application

Transport

Internet

Network
Access

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Internet protocol stack

Application Layer

:



Data











Transport Layer

Header

:


Header Data












Internet Layer

:


Header Header


Data












Network Access Layer
:

Header Header Header Data














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Network Access Layer










provide the means to deliver data to other device


Encompass functions of Network, Datalink and
Physical in OSI Reference Model


Many access protocol


one for each physical
network. New hardware needs new protocol.
Typically show as device drivers and related
programs.


Functions:


Encapsulation of IP datagrams to frames


Mapping IP addresses to physical addresses.



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Internet Layer


Internet Protocol (IP) is the most important in this layer


IPv4 and IPv6


Internet Protocol Functions


Defining the datagram


Defining the Internet addressing scheme


Moving data between Network Access Layer and the Transport
Layer


Routing datagrams to remote hosts


Performing fragmentation and re
-
assembly of datagrams.


IP is connectionless protocol


IP depends on other layers to do error detection
and error recovery


some time called unreliable
protocol

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The Datagram

Version

IHL

Type of
Service


Total Length

Identification

flags

Fragmentation
offset

Time to
Live

Protocol

Herder Checksum

Source Address

Destination Address

Options

Padding

Data begins here

IP datagram format


1

2

3

4

5

6


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Datagrams


IP delivers by checking destination address


Host on same network, diver directly


Otherwise, routing via gateway


Routing datagrams


Host
-
> gateway
-
> gateway …
-
> host


Fragmenting datagrams


Maxium transmission unit (MTU) for each type of
network


If the datagram received from one network is longer
than the other network’s MTU, it must be divided into
smaller fragments.


Header word 2 contains info that identifies which
datagram and info how to re
-
assemble them


Identification


what datagram the fragment belongs to


Offset


what piece of the datagram


Flag


more fragments bit


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Passing datagrams to the transport layer


Done by using protocol number from word3



Internet Control Message Protocol (ICMP)


Part of internet layer


Uses the IP datagram delivery facility to send
message


Functions


Flow control


ICMP Source Quench Message, ask
source to stop sending temporarily


Detecting unreachable destinations


Destination
Unreachable Message for host and port


Redirecting routes


ICMP Redirect Message


Checking remote hosts


ICMP Echo Message


Ping

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Transport Layer


Two most important protocal


Transition Control Protocol (TCP)


Reliable data delivery


User Datagram Protocol (UDP)


Low
-
overhead, connectionless datagram delivery


UDP


No techniques in the protocol to verify data
reached the other end


16
-
bit sort port and destination port


Why use UDP?


Small data


Query
-
response model application


Application provide their own techniques for reliable
data delivery


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Transport Layer


UDP Message format


Source Port

Destination Port

Length

Checksum

Data begins here

0 16 31

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Transport Layer


TCP


Reliable


Positive Acknowledgment with Retransmission (PAR)


connection
-
oriented


Establish a logical end
-
to
-
end connection


Three
-
way Handshake before data is transmitted


Host A Host B

SYN


SYN,ACK


ACK,data





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Transport Layer


TCP



Byte
-
stream data


TCP views data as continuous stream of bytes


Sequence Number and Acknowledgement Number
keep track of the bytes


Exchanging initial sequence number (ISN)


random
number


First byte of data has Sequence number ISN+1


Sequence number identifies the sequential position in
the data stream of the first data byte in the
segment.


Acknowledgment Segment (ACK)


Positive acknowledgement


Flow control
-

window


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Transport Layer


TCP segment format


Source Port

Destination port

Sequence Number

Acknowledgement number

Offset

Reserved

Flags

Window

Checksum

Urgent Pointer

Options

Padding

Data begins here

0 16 31

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Application Layer


Included all processes that use the Transport
Layer protocols to deliver data


telnet


Remote login over network


ftp


File transfer protocol for transferring files between hosts


SMTP


Simple Mail Transfer protocol, which delivers electronic
mail


HTTP


Hypertext transfer protocol, delivers web pages over the
network.


Domain Name System (DNS)


Map IP addresses to the names assigned to network
devices.

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Application Layer


Network File System (NFS)


Allows files to be shared by various hosts.


Programming network application: socket API

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Summary

We’ve talked about


TCP/IP and Internet


TCP/IP four layers: applications, transport,
Internet and Network Access.


Next, we will look how IP datagram moves
through a network when data is delivered
between hosts.