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GIP Renater
Architectureof the Internet
Jacques PrvostGIP Renater
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What is the Internet made of ?
What is the Internetmade of ?
a few reminders : ISPs, GIX, Operators, QoS
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The Internet, a huge number of networks
The Internet :uSomething like a world-wide service, not a
network!
uBased on :
S IP protocol (today its version 4, soon its version 6)
SA huge number of networks : ISPs : Internet ServiceProviders :
From very local ones : campus networks, MANs
To very large ones : nation-wide, world-wide
SEverybody can exchange data with everybody else :
There are a number of Global Exchange Points : GIX, to which the
main ISPs connect. Smaller ISPs reach them through these mainISPs.
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The Internet, a huge number of interconnected networks
ISP
ISPISP
ISP
ISP
ISP
ISP
ISP
ISP
ISP
ISP
ISP
ISP
ISPISP
ISP
GIX
GIX
GIX
GIX
ISP
ISP
ISP
ISP
ISP
ISP
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An ISP network : routers and links :
IP router
LinkNOC
Network Control
Other ISPs, users
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An ISP network : the NOC :
NOC : Network Operation CenteruAdministration and day-to-day operation of the
network, monitoring etcSExample : receive error information / complaints from other
ISPs and users, then act on routers and/or telecomoperators (if link down) to set it right again
Network
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Infrastructure and the Internet
ISP
ISP
ISP
ISP
ISP
ISPISP
Infrastructure operators(undersea fiber opticcables, railways )
Telecom operators
Internet serviceproviders
They use the services
provided by :
They use the servicesprovided by :
IP services
Links
Infrastructure(cables)
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A few reminders about infrastructure
The Internet can use any type of infrastructure.
Typically, for medium or long distance links :
u Optical fiber : up to hundreds of Gbit/s
S Terrestrial or undersea
u Copper cables : hundreds of Mbit/s
u Satellite :up to hundreds of Mbit/s
S usefull where terrestrial links are scarceS Costly !
Short distance (campus, town) :
u Fiber
u Radio
u ADSL (the so-called high speed Internet : hundreds of
kbit/s)u TV cable networks
u Power lines : ?
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Who decides the architecture of the Internet :
The ISPs and only the iSPs .Their decisions (i.e., the architecture of the Internet) is
mainly based on :
uTraffic flows and corresponding revenues,
uAvailability and cost of infrastructures that
telecom operators provide.
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Who decides the technology of the Internet :
Advanced user communitiesuUniversities, research centres
SMainly in US, Canada, large European countries
Advanced routing hardware manufacturersSMainly in US and Canada, + recently a few start-ups in
Europe
Large ISPs providing advanced servicesSHave to decide if what universities and manufacturers
propose is really good for operational and commercialservices. Not always so
STHEY decide, because in the end it is THEIR money
IETFu Internet Engineering Task Force
S Internet standards (RFCs)
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Basic Internet services
Basic services :Adressing
NamingRouting
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Addressing, naming and routing
Addressing :uEach object (router , station) has a unique IP
address :S IPv4 : 123.210.012.111
As the Internet explodes, not enough IPv4 addresses available
S IPv6 : much larger address space
uAddresses are attributed by ICANNS In Europe, delegated by ICANN to RIPE
S ISPs obtain from RIPE blocks of addresses
SThey attribute these addresses to their customers But addresses still belong to the ISP
SEach customer attributes individual addresse(s) to its end-users
If not enough addresses available (IPv4) use address translation :complicated
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Addressing, naming and routing
Routing :uHow to route datagrams from the sender to
the destinee
uBased on IP addresses + logical topology of the
ISPs networks + policy rules
uRouted from router to router according to routinginformation as known by each router
uProtocols for passing routing informationbetween routers :
S Inside Autonomous Systems (AS) (an isp network, or
part of a large ISP network) :
SBetween AS : BGP etc
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Addressing, naming and routing
Naming :u Each object in the Internet has (or can have) a unique name
:
S Example : www.Paris.ENSAM.fr Fr : top-level domain name
ENSAM : domain name
Paris : sub-domain name : the Paris center of ENSAM
www : the machine inside Paris.ENSAM.fr
u Correspondance domain name IP address :
S Done by DNS : Domain Name Servers.
u Attribution of domain names :
SWorld-wide : ICANN
SWithin Top-level domain FR : by AFNIC (non-profit institution)
SWithin ENSAM and its sub-domains : by ENSAM
S A domain name belongs to the user organism, not to its ISP
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Advanced services : a few examples :
Advanced services :Quality Of Service
MulticastIPv6
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Advanced services : QoS
QoS : Quality Of ServiceWhat happens when a network component is
overloaded ?
uWhat happens depends on which scheme of
Quality of Service the ISP applies :
Overloadedlink
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Advanced services : QoS
QoS :uBest Effort : all traffic has the same priority. This
is the default strategy (i.e. : no QoS service)
SPackets are dropped, jitter appears (variable wait time in the
router) :
Overloadedlink
Queing
Packets dropped
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Advanced services : QoS
QoS :uProblems with Best Effort : not acceptable for
real-time : audio, video
SNon-real time applications :
TCP (Transport Connection Protocol) asks for re-sending lost packetstill all are received correctly
TCP is asynchronous, so jitter does not matter
TCP always gets the data without error, but may take a lot of time todo it
SReal-time applications :
No time available for re-sending (hence no TCP)
Too much jitter packet arrives too late and the application cannot
use it :packet dropped at the receiving application level Consequence : overloaded network --> visible and audible bad quality
on audio and video
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Advanced services : QoS
Effective QoS :uStrategy 1 : infinite (or almost) bandwidth
SEnsure that packets are almost never dropped
Real-time applications can usually cope with
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Advanced services : QoS
Effective QoS :uStrategy 2 : different links for different traffics :
STraffic which needs quality is usually a small part of overall
traffic.
SDedicate separate links to it, with enough bandwidth :
uWhere :SCore networks of large or medium-size IP networks
Ordinary traffic, acceptsoverload
Quality traffic no overload
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Advanced services : QoS
Effective QoS :uStrategy 3 : differentiated classes of service
(DiffServ):
STraffic which needs quality is usually a small part of overall
traffic.
SIt gets priority in routers : no drop; less jitter
uWhere :
SEverywhere in IP networks
Overloadedlink
Queing
Packets dropped
Priority traffic
Ordinarytraffic
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Advanced services : QoS
Effective QoS : difficulties :uTo be effective, QoS must be implemented
coherently from end to end
SThough end-to-end usually goes through several (5, 10, or
more) different IP networks
S
How to get them to agree to a given scheme ?uThen who pays for it, to whom, and how ?
Today, QoS is still at the experimental or pilot level.Not yet operational (at least on large scale).
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Advanced services :multicast
Unicast :uThe usual, simple way for routing a datagram :
SOne sender, one receiver
Multicast :
uOne sender, several or many receivers
SThe network routers duplicate the datagrams when needed
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Advanced services :multicast
IP router
Link
Sender
Receiver
Unicast
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Advanced services :multicast
IP router
Link
Sender
Receiver
Multicast
Receiver
Receiver
Receiver
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Advanced services :multicast
A multicast session is somewhat like a TV channel :SOne sender, a number (not restricted) of receivers
SA receiver can join or leave the session at any time, the
networks reconfigures the multicast routing automatically
and immediately.
SA session is identified by a session identifier :
Looks, feels and tastes like an IP address
But is not an address, but a logical TV channel number
SThe network automatically sets the correspondance between
the session identifier and the relevant IP addresses on
sender and receivers.
Main usage : videoconferencing, interactive remote
teaching.
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Advanced services : IPv6
The next generation of the InternetAlready there on a pilot basis
uRefer to specific presentation within this cursus.
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Fin de la prsentation
F in?
Questions