ISPs, Backbones and Peering 14-740: Fundamentals of Computer Networks Bill Nace Material from Computer Networking: A Top Down Approach, 6 th edition. J.F. Kurose and K.W. Ross
Administrivia • Norton2010 Paper Review for today • Lab0 is posted 2
Last Lecture • Internet TCP/IP architecture • Layering not strictly enforced • “Hourglass” -- IP ueber alles • Allows rapid innovation at layers below • Flexible applications / services above • IETF process • “Rough consensus and running code” • End-to-end argument • Does it still apply? 3
Another take on Layered Architecture
traceroute • ISPs and Backbones • Peering and Settlements • Peering Evolution • Interconnections 5
A Packet’s Journey • Packets travel across many networks • Particular protocols will be studied later • This lecture motivates why routing mechanics are necessary A CMU Pgh B PennRen C Little ISP G Some NW D H Huge ISP Tier 1 ISP Tier 1 F ISP Some ISP Tier 1 ISP Cheap ISP E CMU Kobe J 6
CMU’s Infrastructure • Two 10 Gigabit Ethernet links (singlemode fiber) to Pittsburgh PSC Internet2 Supercomputer Center • From Cisco 6500s located in Cyert Level3 Comodity PennRen Internet and Stever House 10Gbps 1Gbps/10Gbps • “Redundancy” links to PennRen / 1Gbps 10Gbps External Level3 over 1Gbps rate-limited 10 Gigabit Ethernet Internal • Money • $40K per year to PennRen • A PA state education network CMU Internal • $100K to PSC, $100K to Level3 • $300K per year on fiber leases
Backbones • In the beginning ... of Internet time • Single backbone: NSFNet • Everyone on the “Internet” was on NSFNet • A backbone network enables all connected end-hosts (users and companies) to communicate with each other • No interconnection problems 8
Backbones (2) • Commercial backbone providers emerged • Technology transfer! • A “Good Thing” • If US Government was managing the Internet, might not be so successful • We all expect universal Internet connectivity 9
Interfaces: Transit • Transit / provider-customer • ISP sells access to another ISP or company • e.g. CMU buys transit (or access to Internet) from Level3 10
Interfaces: Peering • Reciprocal access to each other’s customers • Usually free exchange of tra ffi c • DO NOT serve as transit for 3rd party data • E.g. Google and MSN peer with each other, so email messages between Gmail and Hotmail are transferred directly, without going through their transit providers • These relationships are confidential business secrets • Roughly hierarchical, though the topology is flattening 11
Tier 1 ISP • Internet backbone providers • Peers with every other Tier-1 in “Internet Region” • Who is a major ISP in your country? • US? • India? • China? • Careful: “Tier-1” is an overloaded and misleading term 12
Images courtesy of Level-3
>4200 networks in 142 nations, many at OC-768 speeds Images courtesy of Verizon
Tata: "Discover the World's Largest Global Footprint" Image courtesy of tatacommunications.com/network
“Typical” Infrastructure • High speed links • Level3 operates 40Gbps DWDM networks • High performance routers • Over-provisioned bandwidth • 40 ms delay within region • <1% packet loss • Global presence (or at least multi-continent) 16
“Typical” Tier-1 Relationships • Directly connected to other Tier-1 ISPs (i.e. peer with) • Connected to a large number of Tier-2 ISPs • Vertically integrated: sell services directly to customers • International in coverage • Ecosystem: do not buy transit from another provider in order to reach the whole Internet 17
Why do Tier-1 ISPs need to peer with each other? • No single Tier-1 ISP can reach the whole Internet on its own • Internet is a network of networks • But Tier-1 ISPs have a restrictive peering policy • Do not peer with other non-Tier-1 ISPs • They are potential revenue generating customers • No incentive to accept additional peers 18
What is a Tier-2 ISP? • Network infrastructure is usually regional • Customer of Tier-1 ISP(s) – needs to buy transit • Provider of customers – also re-sells this transit • Peers with other Tier-2 ISPs – settlement free Tier-2 ISP pays Tier-1 Tier-2 ISP for connectivity to rest Tier 1 of internet ISP Tier-2 ISPs also peer Tier 1 ISP Tier-2 ISP privately. Interconnection Tier-2 ISP can be direct or via IXP IXP Multi-connection Tier 1 ISP relationships possible Tier-2 ISP 19
Thinking time • Why do Tier-2 ISPs need to buy transit from a Tier-1 provider? 20
Thinking time • Why do Tier-2 ISPs peer with each other? 21
Open Peering Policy • Tier-2 ISPs have an open peering policy • Peer with anyone possible • Costs of peering have to be balanced against gains for a Tier-2 ISP • Management cost: usually settlement-free peering means both parties should send approx equal amounts of tra ffi c to each other • Maintenance cost: extra equipment, transmission capacity to meeting point, exchange and other fees 22
Content Providers • Do not sell transit • Category A: Focus on content creation • Do not want to operate a network • Do not have expertise in maintaining peering relationships — router, policy, negotiations, … • No Peering Policy • Category B: Sophisticated, large-scale players • Use peering to improve user experience • Open Peering Policy 23
Peering Ecosystem Internet Region Full Mesh Tier 1 ISPs Transit Free Peering Partial Mesh Must Buy Tier 2 ISPs Peering Transit Generally Must Buy Content / Enterprise Companies No Peering Transit Things are never so clear-cut . . .
traceroute • ISPs and Backbones • Peering and Settlements • Peering Evolution • Interconnections 25
US Evolution • 1999/2000 economic collapse • Telecom sector • Need to rethink their business model • Need to cut costs • General dotcom bust • Lots of cheap equipment on eBay • Transit rates drop • Upstream provider @Home for cable companies went bankrupt • Peer-to-peer file sharing grows exponentially in popularity 26
Transit Prices are Falling • Price per Mbs ➙ 63% per year decline • Luckily, volume is increasing even more • Somewhat bad for Tier-1 ISPs 27
Content Companies are Peering • Network savvy, large scale enterprises • MSN, Yahoo, Google, Ebay, Walmart, … • Yahoo has an open peering policy • Reduce transit costs • Improve end-user experience • Good for content companies • Bad for Tier-1 ISPs 28
traceroute • ISPs and Backbones • Peering and Settlements • Peering Evolution • Interconnections 29
Interconnection • How do two networks interconnect with each other? • We are talking about routers in two di ff erent companies, under separate administrative control 30
Public Peering • U.S. government decided to let commercial companies take over management of the backbone networks • 1991: Commercial Internet Exchange (CIX) • 1 router in Santa Clara, CA • 1995: Network Access Points (NAPs) in SF , Chicago, NY, D.C. • More recent: Internet Exchange Point (IXP) • 30 in US, 6 in Japan • “More is good” because of congestion, at one point 20% of tra ffi c going through the 1st NAP was dropped! 31
ISP Connections Tier 1 Tier 1 ISP Tier 1 ISP ISP Tier-1 providers interconnect privately (Peer) IXP Tier 1 ISP (Meet-me room) Tier-1 providers also interconnect at Internet Exchange Points (IXP) (30 in US)
Private Peering • Two networks bypass IXPs and directly peer • In response to congestion at some IXPs • Business reasons • Also more cost-e ff ective • There are limited number of IXPs at major regions • Can privately peer in other locations • Sometimes take a hybrid approach • Public exchange for some peers • Private meeting point for others 33
Provider-customer Interconnection • Point-of-presence (PoP) • Customer typically leases a high-speed link from a 3rd party telecomm provider • Directly connects a router at a provider’s PoP 34
Various Methods • How do two networks interconnect with each other? • Many methods: Public Peering, Private Peering, Provider-customer PoP • There are really no industry-specific regulations, mostly purely driven by commercial and economic forces 35
How does the world connect to Facebook? Facebook’s network IXP in Germany IXP in Sweden Level3 Directly Connected Peer? IXP in Japan Amazon Image courtesy of Teun Vink (teun.tv)
Lesson Objectives • Now, you should be able to: • analyze business practices of various enterprises using the multi-tier network model (Tier-1, 2, etc) and common peering practices • describe the relationships and associated motivations for enterprises on the internet • analyze the e ff ect of recent trends in internet usage patterns on the various business enterprises on the internet • describe interconnection methods between enterprise networks 37
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