Download network Access Layer

Internet
Protocol Architecture
Chapter 2
The Internet

Internet evolved from ARPANET
 Developed
in 1969 by the Advanced
Research Projects Agency (ARPA) of the U.S.
DOD
 First operational packet network
 Packet network also applied to tactical radio
& satellite nets  need for interoperability
led to standardized TCP/IP protocols
 Internetworking standards was proposed by
Vint Cerf and Bob Kahn (TCP/IP)
Key Elements
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Hosts: computers,
mainframes,
workstations, etc.
Ethernet Switch:
Connecting hosts in a
LAN (multiple
segments)
Routers: Connecting
LANs and WANS
Each segment can be a separate building
http://www.querycat.com/question/f3d88ef267ad2505f6e7cfe3061aaca3
Cisco's Catalyst Switch
Key Elements
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ISP (Internet service provider)
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Regional ISP
Backbone ISP
CPE (customer premises equipment): modems, DSL, cable
modem, satellite
NAP (network access point): One of the major elements
connecting ISPs
Last mile (or local loop): physical path (infrastructure)
between the host and the ISP – coax. Copper, etc.
POP (point of present): ISP site with communication
equipments
NSP (network service provide): The company that provides
backbone services to ISPs
Internet Architecture
http://navigators.com/internet_architecture.html
Internet Architecture
Example Configuration
Assume
-Company C, located in San Francisco,
-Has 5 hosts
-Connected to an ISP Y
-David located in NY
-Connected to ISP Z
-Uses DSL
http://www.vtc.com/products/TCP/IP-for-Windows-tutorials.htm
- Company A runs the NAP in West coast
And company B runs the NAP in East Coast
-Peer agreement
Show:
POPs
CPE
Regional ISP
Example Configuration
Assume
-Company C, located in San Francisco,
-Has 5 hosts
-Connected to an ISP Y
-David located in NY
-Connected to ISP Z
-Uses DSL
- Company A runs the NAP in West coast
And company B runs the NAP in East Coast
-Peer agreement
Show:
POPs
CPE
Regional ISP
Network Protocols
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Protocols define format, order of messages
sent and received among network entities, and
actions taken on message transmission
Set of rules or conventions that allow peer
layers to communicate
Key features

Syntax (format of the data)
 Semantics (Control information, error handling)
 Timing (sequencing and synchronization)
How Does a Protocol Work?
A human protocol and a computer network protocol:
Hi
TCP connection
request
Hi
TCP connection
response
Got the
time?
Get http://www.awl.com/kurose-ross
2:00
<file>
time
Open Systems Interconnection - OSI

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Developed by the
International
Organization for
Standardization (ISO)
Has seven layers
Is a theoretical
system delivered too
late!
TCP/IP is the de facto
standard
Peer layers communicate
with one another
Open Systems
Interconnection - OSI
TCP/IP Protocol Architecture
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Developed by US
Defense Advanced
Research Project Agency
(DARPA)
For ARPANET packet
switched network
Used by the global
Internet
Protocol suite comprises
a large collection of
standardized protocols
TCP/IP Layers
 Application
layer
 Host-to-host, or
transport layer
 Internet layer
 Network access layer
 Physical layer
Physical Layer Protocols

Responsible for transporting the
information

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encapsulating information and
getting it ready for transportation
Deals with physical interfaces,
electrical parameters, pin outs,
number of twists per foot, cable
gauge, data rate, signal integrity,
etc.
Examples: RS-232, V.35, RJ-48,
DS3, OC-n, High Speed Serial
Interface
Physical Layer Protocols - Examples
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RS-233
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Interfacing computer to modem
Supports speeds up to 9.6 Kbps
25-pin or 9-pin interface
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V.35
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RJ-48
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Physical interface for T1 and E1
Defined by G.703 standards

Uses coaxial cable
Supports 45 Mbps
OC-n
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Serial interface between the
terminal and the digital
communication equipment (T1)
 Supports speeds above 19.2 Kbps
DS3
Fiber optic interface
n can be 1,3,12,etc.
Multimode or single mode
High speed Serial Interface
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Supports 42 Mbps
Interfacing ATM switches
Data Link Layer Protocols
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Frame and format information according to some
standards
Two basic categories

Connection oriented Technology
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Establishing pre-defined virtual path upon request
Many different virtual paths can reside on a physical link (like a
highway system)
Example: ATM and Frame Relay Protocols
Connectionless Technology
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Only source and destination addresses are defined
No pre-defined path exists between devices
The actual routing path can be different depending on the network
status
Example: High-level Data Link Control (HDLC)
Network Protocol Layers
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Transporting individual packets of information
through the network end-to-end
Can route packets according to actual device
address or network topology (connectionless)
Routing is done according to the network
manager or by a dynamic routing protocol
Without Network layer all routings will be pointto-point
Examples:
 Internet Protocol (IP) used on Internet
 Packet-based; Connectionless
 IPX developed by Novel used in LAN
 Packet-based; Connectionless
Transport Protocol Layers
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Interfacing the upper layers to lower layers
Formats applications into segments
Examples: TCP and UDP Offers end-to-end flow
TCP
 Provides
reliable delivery of data
 Keeps track of packet order

UDP
 User
Datagram Protocol
 Does not guarantee delivery
 Offers faster data delivery
Application Layer
provide support for user applications
 need a separate module for each type of
application

TCP/IP Applications
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Simple Mail Transfer Protocol (SMTP)
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File Transfer Protocol (FTP)
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Provides basic electronic mail
Only sends (forwards) mail
Uses TCP
Used to send files between systems – file transfer
Uses TCP connect to check the ID and PW
Establishes another TCP connection for data transfer
Telnet
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Provides remote login
Implemented in two modules: User and Server
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User Telnet: Interacts with terminal I/O module
Makes the remote terminal appear as local terminal
TCP/IP Applications
Operation of TCP and IP
Addressing
Requirements
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Two levels of addressing
required
Each host on a subnet
needs a unique global
network address

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called IP address
each application on a
(multi-tasking) host needs
a unique address within
the host

known as a port
Subnets: attached devices
Defined by the network
Access Layer
Operation of TCP/IP
Process at A hands the
message to TCP layer:
Send the message to
host B port 2
TCP hands the message
to IP – destination will
be Host B
IP hands it to network
Layer -> next hop is
router J
Conditions
The signal format
For the physical path
Operation of TCP/IP
Data from the
applications software
Header contains:
Destination port,
sequence number
Checksum
Header contains:
Destination of the host address
Header contains:
Destination subnet address –
which attached device
Facility request: e.g., priority
Transmission Control Protocol (TCP)
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Standard transport layer for Internet is (TCP)
Provides a reliable connection for transfer of
data between applications
A TCP segment is the basic protocol unit
 Logical
connection between peer layers
 TCP provides host-to-host connection (port-to-port)

TCP tracks segments between entities for
duration of each connection
 Segment
flow
TCP Header
User Datagram Protocol
(UDP)
An alternative to TCP
 No guaranteed delivery
 No preservation of sequence
 No protection against duplication
 Minimum overhead
 Adds port addressing to IP

 That
is why we need it!
UDP Header
IP Protocol
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IPv4
 Addresses
are 32 bits wide
 Its header is 20 bytes at minimum
 Uses doted-decimal notation (e.g. 43.23.43.56)

IPv6
 Provides
larger address domain; addresses are 128
bits wide
 Multiple separate headers are supported
 Handles audio and video; providing high quality paths
 Supports unicast, multicast, anycast
IP Header
IPv6 Header
OSI - review
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Open Systems
Interconnection
developed by the
International Organization
for Standardization (ISO)
has seven layers
is a theoretical system
delivered too late!
TCP/IP is the de facto
standard
Standardized Protocol
Architectures
Each layer must interacts with three
Other layers
Protocols define which services are
Provided
Providing services to N+1
Multiple services:
Each service has an address:
Called Service access Point
Service Primitives and
N
N-1
Parameters
Adjacent layers
provide services to
one another:
 Primitives to specify
function performed
 Parameters to pass
data and control info

N-1
N
Elastic and Inelastic Traffic
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Elastic traffic
 can
adjust to delay & throughput changes
over a wide range
 eg. traditional “data” style TCP/IP traffic
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Inelastic traffic
 does
not adapt to such changes
 eg. “real-time” voice & video traffic
 need minimum delay requirements
General Traffic Characteristics
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Throughput
 Amount
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Delay
 Time
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of data carried over time
it take to deliver data between hosts
Delay Variation
 Variation
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in the time when delivering the data
Packet Loss
 Packets
not made it to the destination
Media Types
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Text, Audio, Graphic, and Video
Different technologies are required to support
various media types
Examples of multimedia technologies
 Compression:
JPG for images, MPG for video
 Transmission and networking technologies
 Protocols: RTP (real-time transport protocol)
 Quality of service (QoS) – providing different levels of
services to different applications

Watch this:
 http://www.vtc.com/products/TCP/IP-for-Windows-
tutorials.htm

TCP/IP Applet
 http://www.kom.e-technik.tu-
darmstadt.de/projects/iteach/itbeankit/Applets/TCP/tc
p.html

Simple TCP/IP Lab
 http://www.windowsnetworking.com/articles_tutorials/t
sttcpip.html?printversion