Internet Architecture: A High-level Overview AFIX Technical Workshop Session 1.

Internet Architecture: A High-level Overview

AFIX Technical WorkshopSession 1

AFIX Technical Workshop: Session 1

Outline of content The underlying structure of the

Internet and the forces that have shaped it.

The concepts of peering and transit A general overview of exchange

points (IXPs) The state of IXPs and peering in Afrca


History: Where it all started Way back in the dawn of Internet time

(1969!): ARPANET 1972 DARPA-sponsored “Internetting

project” to develop communication protocols for linked packet networks.

TCP/IP written early 1970s


Some key decisions Independent networks: no modification to

reach Internet Networks linked by gateways which

transmit data packets but retain no information about traffic

Use the fastest available route for each packet

Gateways to route traffic without discrimination

Operating principles freely available to all


Towards the net as we know it 1970s: e-mail, first small-scale commercial

services, Usenet, Unix networking for universities

1980s: Bitnet, CSNet, EuNet, EARN. Internet hosts: 1969 – 4

1981 – 210 1984 – 1,0001986 – 5,0001987 – 28,0001989 – 130,000


Key growth enablers The Domain Name System (DNS)

Replaced single static host file database with dynamic hierarchical structure.

NSFNet US backbone for all university traffic. Broke bottleneck, encouraged use. Exclusion of commercial users encouraged

growth of private ISPs (UUNET 1987).


1990s: Birth of the web 1990: Hosts grew to 300,000

Archie (first search engine) 1991: Private access to NSFNet

Tim Berners-Lee developed HTTP and HTML

Internet: A network of networks (infrastructure)

Web: Information space – abstract!


Network Access Points 4 original NAPs, all in US, to provide

access to NSFNet (“onramps”) Regional access providers developed

to aggregate traffic – direct interconnection led to NSFNet obsolescence.

Multiplication of peering and exchange points


The role of IXPs today The Internet would not exist without

agreements to exchange traffic!!! Competitor ISPs must co-operate to

serve their clients Two main forms of traffic exchange:

Transit – sell access to all destinations in routing table

Peering – access to each other’s customers


The transit relationship


The peering relationship


To peer or not to peer?

Pros Cons

Lower transit costs Traffic asymmetry

Lower latency Loss of transit sales

Increased usage Resource use

ISPs can offer more and better services

No service guarantees

Increased customer satisfaction


“The overall structure of the Internet is one where there is a strong business pressure to create a rich mesh of interconnection at various levels”

Less easy for African ISPs to peer with international providers who’d rather sell transit!


The Internet without peering


Backhaul is expensive for both parties Not cost effective

InternetInternet

AABB

The Internet without peering


Domestic interconnectionInternetInternet

AABB

IXPs shorten the chain…


..and grow local bandwidth


The rationale for IXPs Two ISPs in a market: Peer directly More than two: Peer at an exchange

point “A facility operated by a single entity to

facilitate the exchange of Internet traffic between three or more ISPs”.

Closer = cheaper, faster, more efficient


How an IXP works

Major providers connect their networks and exchange traffic

High-speed network or switch Simple concept - anyplace where

providers come together to exchange traffic


Exchange points

ISPs connect at Internet Exchange Points to exchange traffic

ISP A

Gateways

IXPISP B

ISP C


Conceptual Diagram of XP

Customer Router

Customer Router

Customer Router

Exchange Point Medium


Why use an Exchange Point?

KEEP LOCAL TRAFFIC LOCAL!! ISPs within a region peer with

each other at local exchange No need to have traffic go

overseas only to come back

ISP A

ISP B

200-900ms

200-900ms

USA

5-20ms

200-900ms


The African picture 1.5Gbps outgoing bandwidth (2002) 13Mbps intra-African!!!

High international tariffs discourage multiple links

Lack of peering has cascading effects – eg many African websites are hosted offshore!


Major issues for the African Internet International bandwidth prices are biggest

contributor to high costs African users effectively subsidise

international transit providers! Fibre optic links are few and expensive

reliance on satellite connectivity High satellite latency slow speed, high

prices Growth of Internet businesses is inhibited


The solution: IXPs for Africa So far, 10 out of 53 countries have

IXPs (2003 count) More IXPs lower latency, lower

costs, more usage Both national and regional IXPs

needed Also needed: regional carriers, more

fibre optic infrastructure investment


Obstacles Current providers (cable and satellite)

have a lot to lose Many of these have close links to

regulators and governments Regulatory regimes on the whole

closed and resistant to change Sometimes ISPs themselves are

unwilling to co-operate


Solutions Education and lobbying! Players: AFRISPA, AFIX-TF, CATIA,

AFNOG This workshop is part of the process Later sessions will deal in more detail

with the practical and political issues.

Internet Architecture: A High-level Overview AFIX Technical Workshop Session 1.

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Transcript of Internet Architecture: A High-level Overview AFIX Technical Workshop Session 1.