Network ManagementNetwork Managementhas always been and always will be essential to

the Internet

Testimony of George OuFormer Network Engineer

www.LANArchitect.net

FCC Broadband Industry Practices HearingWC Docket No. 07-52Stanford UniversityApril 17, 2008

Internet meltdown in Internet meltdown in 1980s1980sLack of adequate congestion control in TCP

allowed too many FTP users to overload Internet around 1986

Van Jacobson created congestion control algorithm for TCP in 1987◦ Congested routers randomly dropped packets to force

every TCP end-point (client) to cut flow rate in half◦ TCP clients then slowly increased flow rate with every

successful transmission until next packet drop◦ Caused all TCP streams to home in towards equal flow

rate◦ Fair bandwidth sharing, but only for applications of its

timeJacobson’s algorithm saved the Internet in 1987

and remains dominant standard after 20 yearsEarly example of managing network congestion 2

World Wide Wait in 1990sWorld Wide Wait in 1990sFirst generation of web browsers

were not optimized for InternetWorld Wide Web turned in to the

World Wide WaitVersion 1.1 of HTTP revamped to

efficiently use resources over 1.0

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Today’s crisis on the Today’s crisis on the InternetInternetVideo-induced congestion collapse

◦ Efficient existing broadcast model migrating to bandwidth-intensive Video on Demand model over IP

◦ Full migration of video could require 100- to 1000-fold increase in Internet capacity

◦ Exponentially more bandwidth required as video bit-rate and resolution increase to improve quality

P2P is the dominant distribution model because most of its content is“free” (read pirated)

Video can fill any amount of bandwidth

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More bandwidth doesn’t More bandwidth doesn’t helphelp

Bandwidth hogs

According to the Japanese Government1% of users account for ~47% of traffic10% of users account for ~75% of traffic90% of users get leftover 25%

The few throttling the many

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Exploiting Jacobson’s Exploiting Jacobson’s algorithmalgorithm

50/50Fair

80/20Unfair

92/8Unfair

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Persistence advantage in Persistence advantage in P2P appsP2P apps

* Corporate VPN telecommuter worker using G.722 codec @ 64 kbps payload and 33.8 kbps packetization overhead** Vonage or Lingo SIP-based VoIP service with G.726 codec @ 32 kbps payload and 18.8 kbps packetization overhead*** I calculated that I sent 29976 kilobytes of mail over the last 56 days averaging 0.04956 kbps

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Weighted TCP: Per-user Weighted TCP: Per-user fairnessfairness

92/8Unfair

50/50Fair

• BT chief researcher Bob Briscoe proposes TCP fix before the IETF to neutralize multi-stream loophole

• Changing TCP takes many years, but it’s even harder to get over a billion devices to switch to new TCP client

• Newer network-based solutions being implemented8

Present solutions use protocol throttling◦ P2P applications use disproportionately large amounts of

bandwidth so they’re throttled to balance them out◦ Use conventional router de-prioritization techniques on P2P◦ Use TCP resets to occasionally stop P2P seeders◦ Potentially affect an extremely rare low-bandwidth P2P user◦ Can be fooled by protocol obfuscation techniques

Future solutions are protocol-agnostic◦ Weighted packet dropping at router and/or fair upstream

scheduling on CMTS accomplishes per-user fairness◦ Only targets bandwidth hogs and forces them to back off◦ Cannot be fooled by protocol obfuscation

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Present and future Present and future solutionssolutions

 Pros  ConsCost free deployment 10% of users throttles 90% of users

down to 25% of resources

 Pros  ConsSolves congestion because users self-throttle for fear of massive ISP bill.

Danger of massive ISP bills for consumer. Makes P2P usage cost-prohibitive. By definition a “Toll road”.

 Pros  ConsOut-of-band deployment with TCP resets or use of common de-prioritization techniques. Results in fairer distribution of bandwidth.

Can be fooled by protocol obfuscation.Possibility of affecting non bandwidth hogs.

 Pros  ConsEqual sharing of resources between users of same tier. Can’t be fooled by protocol obfuscation.

Requires more drastic in-line changes to network. Requires real-time tracking of per-user bandwidth consumption and enforcement of per-user fairness.

Fair

Unfair

Intelligent

Dumb

Reasonable

Unreasonable

Future

Past

What is reasonable network management?

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Network management Network management ensures harmonious ensures harmonious coexistencecoexistenceP2P applications need volume, not

priorityInteractive applications (Web) and real-

time applications (VoIP) want priority and not volume

P2P, Interactive, and real-time applications each get what they want under a managed network

Interactive and real-time apps have small/fixed volume so no matter how much they’re prioritized, they cannot slow down a P2P download.

Unmanaged networks regardless of capacity will always be unfair and hostile to interactive and real-time applications

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