Introduction to The Internet

ISP Workshops

1Last updated 12th February 2019

These materials are licensed under the Creative Commons Attribution-NonCommercial 4.0 International license(http://creativecommons.org/licenses/by-nc/4.0/)

Acknowledgementsp This material originated from the Cisco ISP/IXP Workshop

Programme developed by Philip Smith & Barry Greene

p Use of these materials is encouraged as long as the source is fully acknowledged and this notice remains in place

p Bug fixes and improvements are welcomedn Please email workshop (at) bgp4all.com

2Philip Smith

Introduction to the Internetp Topologies and Definitionsp IP Addressingp Internet Hierarchyp Gluing it all together

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Topologies and Definitions

What does all the jargon mean?

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Definitionsp Network Operator

n An organisation running an IP backbonen Provides access to end users or other network operatorsn Sometimes called a Service Provider or a Network Provider

p ISPn Internet Service Providern Usually commercial, for profit

p RENn Research & Education Networkn Providing access for Universities & Collegesn Non-commercial, educational use only

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Some Icons…

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Router (layer 3, IP datagram forwarding)

Network Cloud

Ethernet switch (layer 2, packet forwarding)

Routed Backbonep Operators build networks covering

regionsn Regions can cover a country, sub-

continent, or even globaln Each region has points of presence

built by the operatorp Routers are the infrastructurep Physical circuits run between routersp Easy routing configuration, operation

and troubleshootingp The dominant topology used in the

Internet today

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MPLS Backbonesp Some operators use Multi Protocol

Label Switching (MPLS)p MPLS is built on top of router

infrastructuren Replaces old ATM technologyn Tunnelling over IP network

p Main purpose is to provide VPN servicesn Although these can be implemented

with other tunnelling technologies such as GRE

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Points of Presencep PoP – Point of Presence

n Physical location of operator’s equipmentn Sometimes called a “node”

p vPoP – virtual PoPn To the end user, it looks like an operator’s locationn In reality a back hauled access pointn Used mainly for consumer access networks

p Hub/SuperPoP – large central PoPn Links to many PoPs

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PoP Topologiesp Core routers

n High speed trunk connectionsp Distribution routers

n Higher port density, aggregating network edge to the network corep Access routers

n High port density, connecting the end users to the networkp Border routers & Peering routers

n Connections to other providersp Service routers

n Hosting and serversp Some functions might be handled by a single router

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Typical PoP Design

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Backbone linkto another PoP

Backbone linkto another PoP

Business Customer

Aggregation

Other Networks

NetworkCore

ISP Services (DNS, Mail, News,

FTP, WWW)

Hosted Services

Consumer Aggregation

Other Networks

Border

ServiceAccess AccessService

Network Operation

Centre

More Definitionsp Transit

n Carrying traffic across a networkn Usually for a fee

p Peeringn Exchanging routing information and trafficn Usually for no feen Sometimes called settlement free peering

p Defaultn Where to send traffic when there is no explicit match in the

routing table12

Peering and Transit example

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provider A

provider Fprovider B

A and B peer for free, but need transit arrangements with C and D to get packets

to/from E and F

IXP-West IXP-East

provider E

Backbone Provider D

Backbone Provider C

peering peering

transit

transit

peering

Private Interconnect

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Provider C

Provider D

Autonomous System 99

Autonomous System 334

border border

Public Interconnectp A location or facility where several network operators are

present and connect to each other over a common shared media

p Why? n To save money, reduce latency, improve performance

p IXP – Internet eXchange Pointp NAP – Network Access Point

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Public Interconnectp Centralised (in one facility)p Distributed (connected via WAN links)p Switched interconnect

n Ethernet (Layer 2)n Technologies such as SRP, FDDI, ATM, Frame Relay, SMDS and

even routers have been used in the pastp Each provider establishes peering relationship with other

providers at IXPn Provider border router peers with all other provider border

routers16

Public Interconnect

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Each of these represents a border router in a different autonomous system

ISP 1

ISP 2

ISP 3 ISP 6

ISP 5

ISP 4

IXP

Operators participating in Internetp Bringing all pieces together, Network Operators:

n Build multiple PoPs in a distributed networkn Build redundant backbonesn Have redundant external connectivity n Obtain transit from upstream providersn Get free peering from local providers at IXPs

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Example Backbone Design

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NetworkCorePoP 1

PoP 4

PoP 3

PoP 2

IXP

PeerPeer

PeerPeer

Backbone LinksUpstream1

Upstream 2

Upstream1

Upstream 2

IP AddressingWhere to get address space and who from

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IP Addressing Basicsp Internet uses two types of addressing:

n IPv6 – the new IP protocoln IPv4 – legacy IP protocol

p Internet uses classless routingn Routers must be CIDR capable

p Classless InterDomain Routingn No routing assumptions made based on the address blockn Engineers talk in terms of prefix lengthn For example: 158.43/16 and 2001:DB8::/32

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History of IP Addressingp Pre-CIDR (before 1994)

n Big networks got a class An Medium networks got a class Bn Small networks got a class C

p The CIDR IPv4 years (1994 to 2010)n Sizes of IPv4 allocations/assignments made according to demonstrated need

– CLASSLESSp IPv6 adoption (from 2011)

n Network Operators get at least one /32n End Sites get /48n IANA’s free pool is depleted (February 2011) – the size of IPv4 address

allocations and assignments is now very limited22

IP Addressingp IP Address space is a resource shared amongst all Internet

usersn Regional Internet Registries delegated allocation responsibility by the

Internet Assigned Numbers Authority (IANA)n AfriNIC, APNIC, ARIN, LACNIC & RIPE NCC are the five RIRsn RIRs allocate address space to Network Operators/Local Internet

Registriesn Operators/LIRs assign address space to end customers or other

Operators

p RIRs address distribution:n IPv6 is plentifuln IPv4 is very limited

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Address delegation hierarchy

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IANA

AfriNIC(Africa)

APNIC(Asia & Pacific)

ARIN(N America)

LACNIC(C&S America)

RIPE NCC(EU,ME,C Asia)

Operators Operators Operators Operators Operators

End Users End Users End Users End Users End Users

Non-portable Address Spacep �Provider Aggregatable� or �PA Space�

n Customer uses RIR member’s address space while connected to Internet

n Customer has to renumber to change providern Aids control of size of Internet routing tablen Need to fragment provider block when multihoming

p PA space is allocated to the RIR membern All assignments made by the RIR member to end sites are

announced as an aggregate to the rest of the Internet

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Portable Address Spacep �Provider Independent� or �PI Space�

n Customer gets or has address space independent of their provider

n Customer keeps addresses when changing providern Is very bad for size of Internet routing tablen Is very bad for scalability of the routing systemn ® PI space is rarely distributed by the RIRs

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Internet Hierarchy

The pecking order

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Global Internet: High Level View

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R4

Global Providers

Regional Provider 1

AccessProvider 1

Customer Networks

AccessProvider 2

Regional Provider 2

Content Provider 1

Content Provider 2

IXP

Detailed View of the Global Internetp Global Transit Providers

n Connect to each othern Provide connectivity to Regional Transit Providers

p Regional Transit Providersn Connect to each othern Provide connectivity to Content Providersn Provide connectivity to Access Providers

p Content Providersn Cross-connect to Access Providersn Peer at IXPs (free traffic to Access Providers)

p Access Providersn Connect to each other across IXPs (free peering)n Provide access to the end user 29

Categorising Network Operators

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Tier 1

Tier 1 Tier 1

Tier 1

$$$$$$$$$$$$$$$

RegionalProvider

IXPAccess

Provider

RegionalProvider

RegionalProvider Regional

Provider

IXP

AccessProvider

AccessProvider

AccessProvider

AccessProvider

AccessProvider

Categorising Network Operatorsp Tier-1 – definition:

n A provider which peers with other Tier-1s and does NOT pay for transitn Caveat:

p Many marketing departments call their service provider a Tier-1 – even though that provider may still pay for transit to some parts of the Internet

p Regional providers often have the reach of Tier-1s but still have to rely on maybe one or two Tier-1s to access the whole Internetn They often provide access too, via in country domestic access networks

p Access providers work exclusively in their locale

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Inter-provider relationshipsp Peering between equivalent sizes of service providers

(e.g. Regional to Regional)n Shared cost private interconnection, equal traffic flowsn No cost peering

p Peering across exchange pointsn If convenient, of mutual benefit, technically feasible

p Fee based peeringn Unequal traffic flows, “market position”

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Default Free Zone

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The default free zone is made up of Internet routers which have routing

information about the whole Internet, and therefore do not need to use a

default route

NB: is not related to where a network operator is in the hierarchy

Gluing it together

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Gluing it togetherp Who runs the Internet?

n No onen (Definitely not ICANN, nor the RIRs, nor the US,…)

p How does it keep working?n Inter-provider business relationships and the need for customer

reachability ensures that the Internet by and large functions for the common good

p Any facilities to help keep it working?n Not really. But…n Technical staff at Network Operators keep working together!

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Operators keep talking to each other...p North America

n NANOG (North American Network Operators Group)n NANOG meetings and mailing listn www.nanog.org

p Latin American Foro de Redesn NAPLAn LACNOG – www.lacnog.org

p Middle Eastn MENOG (Middle East Network Operators Group)n www.menog.org

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Operators keep talking to each other...p Asia & Pacific

n APRICOT annual conferencep www.apricot.net

n APOPS mailing listp mailman.apnic.net/mailman/listinfo/apops

n PacNOG (Pacific NOG)p mailman.apnic.net/mailman/listinfo/pacnog

n SANOG (South Asia NOG)p lists.sanog.org/mailman/listinfo/sanog

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Operators keep talking to each other...p Europe

n RIPE meetings, working groups and mailing listsn e.g. Routing WG: www.ripe.net/mailman/listinfo/routing-wg

p African AfNOG meetings and mailing listn SAFNOG – Southern Africa NOG – www.safnog.org

p Caribbeann CaribNOG meetings and mailing list

p And many country NOGs

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Operators keep talking to each other...p Participation in Peering Fora

n Meetings of the Peering Coordinators of many network operatorsp Planning interconnects between operators, content providers, etc

n Global Peering Forum (GPF)n Regional Peering Fora (European, Middle Eastern, Asian,

Caribbean, Latin American)n Many NOGs host their own Peering Foran Many countries now have their own Peering Fora

p IETF meetings and mailing listsn www.ietf.org

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Summaryp Topologies and Definitionsp IP Addressing

n PA versus PI address spacep Internet Hierarchy

n Local, Regional, Global Transit Providersn IXPs

p Gluing it all togethern Engineers cooperate, common business interests

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Introduction to The Internet

ISP Workshops

41