jp architecture internet

8/4/2019 JP Architecture Internet

1/28

ATHENS Novembre 2002

GIP Renater

Architectureof the Internet

Jacques PrvostGIP Renater

[email protected]


2/28


What is the Internet made of ?

What is the Internetmade of ?

a few reminders : ISPs, GIX, Operators, QoS


3/28


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.


4/28


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


5/28


An ISP network : routers and links :

IP router

LinkNOC

Network Control

Other ISPs, users


6/28


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


7/28


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)


8/28


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 : ?


9/28


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.


10/28


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)


11/28


Basic Internet services

Basic services :Adressing

NamingRouting


12/28


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


13/28



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


14/28



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


15/28


Advanced services : a few examples :

Advanced services :Quality Of Service

MulticastIPv6


16/28


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


17/28



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


18/28



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


19/28



Effective QoS :uStrategy 1 : infinite (or almost) bandwidth

SEnsure that packets are almost never dropped

Real-time applications can usually cope with


20/28



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


21/28



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


22/28



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).


23/28


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


24/28



IP router

Link

Sender

Receiver

Unicast


25/28



IP router

Link

Sender

Receiver

Multicast

Receiver

Receiver

Receiver


26/28



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.


27/28


Advanced services : IPv6

The next generation of the InternetAlready there on a pilot basis

uRefer to specific presentation within this cursus.


28/28


Fin de la prsentation

F in?

Questions

jp architecture internet

Documents