Network vs. Server Issues in end-to-end performance

Christian Huitemahuitema@microsoft.com

June 18, 2000

The Internet grows, and grows…

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1020

3040

5060

7080

90

Jan-97 Jul-97 Jan-98 Jul-98 Jan-99 Jul-99 Jan-00 Jul-00

Number of hosts (millions) in the Internet (Netsizer by Telcordia)

Network versus servers: who is trailing whom?

• Network vs. server performance, today

• State of the network,• The special case of the DNS,• The 10 Gigabit challenge,• Going end-to-end?

Network vs. server performance, today

get address

connect

DNS

accept

prepare

transmit

HTTP GET

receive

close

server

network

delay

Get address only once (cache).Connect only once (HTTP 1.1), Pipeline.

Measuring the components of the web

delayDNS

Web performance estimation, 1998-2000

• For a given client/server pair:– Measure the address resolution delay,

connection delay, delay to first packet, delay to transmission of page

• Repeat every day:– For a fixed set of 100 “large” servers,– For a set of 100 “random” servers,

provided from randomized requests to Altavista, Lycos, Google, etc.

Observed bandwidth seems to grow over time

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20000

40000

60000

80000

100000

120000

140000

Sep-98 Feb-99 Aug-99 Jan-00

median

worst 5%

14 per.Mov. Avg.(median)

The servers seem to contribute 40% of the

delay

0%

10%

20%

30%

40%

50%

12/1/99 1/1/00 2/1/00

Large servers Random servers

Feedback Loop: Why Capacity Doubles Every 8

Months

Providers increase the network capacity

More users, more demand,

faster modems

More contents, more servers,

faster feeds

Network vs. server: what is the state of the

network?

First network characteristic:

Packet loss ratesEvolution of SYN repeat rates

0%

5%

10%

15%

20%

25%

9/4/1998 2/14/1999 7/27/1999 1/6/2000

C > 2s

14 per. Mov. Avg. (C >2s)

Second characteristic:Round trip time

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Jul-98 Nov-98 Feb-99 May-99 Aug-99 Dec-99 Mar-00

Taking a closer look at the round trip time distribution

Density and CFD of "short" connection delays (ms)

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

10 100 1000 10000

1-CFD(x)

density(x)

Likely evolution of the network

• Accommodate growing demand:– Cable, DSL, other broadband– Mobile phones, appliances

• Likely evolution:– Average bandwidth grows -> 100 kbps– Median delays -> distance/speed of light– Delay deviation diminishes, as predicted

by Paul Kenny’s work.

Network vs. server:The special case of the

DNS

DNS: an amplifier of the Internet Performance

Local S

erv

er Root, .Com

Example.Com

Many network traversals, many servers.

Resolution Delay,Random DNS Names

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100%

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DNS delays don’t seem to improve at Internet

Speed…

0%

10%

20%

30%

40%

50%

60%

9/4/1998 2/14/1999 7/27/1999 1/6/2000

D > 2s

C > 2s

14 per. Mov. Avg. (D >2s)

14 per. Mov. Avg. (C >2s)

Fraction of DNS resolution delays over 2 seconds

A clear case of “server vs. network”

• A.ROOT-SERVERS.NET loss: 33.9%• B.ROOT-SERVERS.NET loss: 3.4%• C.ROOT-SERVERS.NET loss: 21.1%• D.ROOT-SERVERS.NET loss: 2.6%• E.ROOT-SERVERS.NET loss: 12.3%• F.GTLD-SERVERS.NET loss: 4.0%• F.ROOT-SERVERS.NET loss: 12.3%• G.ROOT-SERVERS.NET loss: 62.1%• H.ROOT-SERVERS.NET loss: 20.9%• I.ROOT-SERVERS.NETloss: 7.1%• J.GTLD-SERVERS.NET loss: 8.3%• K.GTLD-SERVERS.NET loss: 2.2%

Limits of these data:

One single test,

One single day!

How will the DNS situation evolve?

• No clear virtuous cycle:– Registration of new names is a for profit

venture (NSI, and wannabes)– Maintenance of root is a non profit

service with political constraints (ICANN)• Solutions from servers, software:

– Less reliance on root?– More reliance on caches (load

balancing?)– Less reliance on the DNS!

Network vs. server:The 10 Gigabit challenge

Servers are getting better but is this enough?

• Internet2 Land Speed Record award:– "We hope this competition gets people

thinking about enabling really revolutionary Internet applications," - Jim Gray

– "To realize Internet's full potential, end-to-end network performance needs to take a huge leap forward," - Gordon Bell

• The records: – 751.362 Mbps over 5,626 km (single TCP)– 957.369 Mbps over 5,626 km (2 TCP)

The 10 Gigabit challenge, or the limits of Moore’s

law

02468

1012141618

2000 2001 2002 2003

Backbone (9months)

Fiber (10months)

Moore's law (18months)

Meeting the challenge:part 1, ever better servers• Get stronger:

– Faster CPU, better memory architecture– Faster I/O

• Get smarter:– HTTP 1.1, TCP, IPv6…– Better protocol design(s)– Better software (doing that)

• Get help:– Offload packet processing (done that)– Offload encryption (done for IPSEC)– Offload key management (uh?)

Meeting the challenge:part 2, larger clusters

• Servers x2 every 18 month. • Can we manage a cluster of 100,000

servers?– Load balancing, Software upgrade, Failover

• Can we develop distributed applications?

Meeting the challenge:part 3, distribution

networks

• Push the “content” near the “consumers”

• Is this needed in a 10 Gigabit world?• Does it work for more than GIF files?

Evolution of server, server farms and distribution

• Handling variability– Heavy tail distribution of demand means

flash crowds, etc.– Could incite to a “market of servers”, or to

“adaptive servers.”

• Pushing up hill– Need a serious business case for investment

in new servers– Constantly testing the limits of the

technology

Network vs. server:Going end-to-end?

End to end distribution:NAPSTER, Gnutella

Rendezvous, directory

End to end communication: real time

audio, video, gamesSIP proxy

SIP proxy

Meeting the challenge:distribute the load!

• The return of the end-to-end argument– Each new client brings its own

resource– The only known way of scaling

• Only place in the servers the functions that cannot possibly placed in the client!

Network vs. server:Thank You!