CDN technology overview

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CDN

CDN Technology overview2016.03 | Product Management team |

Internet Technology BasicsCDN OverviewCaching technologyAcceleration technology

1. Internet Technology Basics

Internet Basics ( ) TCP/IP (Transmission Control Protocol/Internet Protocol) .

(WWW) HTTP (Hyper Text Transfer Protocol) , HTTP Microsoft Internet Explorer, Mozilla Firefox, Google Chrome .

(Hypertext) () .

, , , , , .

, , , , .

, RSS .

(IM), , SNS . | ,

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Web BrowsingInternet

Hey, 213.236.208.98, show me your home page.HTTP 200 OKHere you go:... Domain name , IP .

IP , Contact name mapping , Domain name (. www.google.com) IP mapping DNS (Domain Name System) .

TCP , , , .

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DNS Basic Operation DNS IP . Domain name IP DNS.

DNS ( Page ) www.test.com , PC DNS ( DNS Local DNS ) www.test.com hostname IP . Local DNS www.test.com IP , Local DNS ( ) IP . Local DNS IP Local DNS www.test.com IP DNS . Root DNS www.test.com IP . Local DNS Root DNS (IP) . (Root DNS 13 Root DNS Mirror 3 .)Root DNS www.test.com IP Local DNS .com DNS .Local DNS .com DNS www.test.com IP , .com DNS , .com DNS test.com DNS .Local DNS test.com DNS www.test.com IP , test.com DNS www.test.com hostname IP , 173.194.33.17 . LDNS www.test.com IP IP . | , DNS

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DNS Basic Operation Local DNS DNS (Root DNS - .com DNS test.com DNS ) Recursive Query

TerminologyURL: http://www.test.com/index.html Hostname: www.test.com Top level domain name: .comSecond level domain name: test.com | , DNS

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Cache (Cache) , .

(Cache memory): CPU .

ARP (Address Resolution Protocol) : TCP/IP Destination IP Destination MAC (Media Access Control) ( ) Destination MAC ARP . (PC, , , ) IP MAC ARP .

DNS : IP DNS , ARP IP , DNS IP . DNS DNS .

: . | NRC LIVE , , 2002

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Web Cache (Web Cache) . . . (Origin server) .

(Accelerator) . | NRC LIVE , , 2002

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Forward Cache System (Forward Cache): . . , .

. . (1 (edge server) () (Origin Server) ) | NRC LIVE , , 2002

www.cdnetworks.comwww.daum.netwww.naver.com...

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Reverse Cache System (Reverse Cache): . .

IP . ( Origin IP .) jsp (Origin ) .

(Web Accelerator) . | NRC LIVE , , 2002

Reverse cache = 192.168.10.1W1=192.168.10.2W1=192.168.10.3W1=192.168.10.4

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Transparent Cache System (Transparent Cache): Transparent () . ( ) .

. . | NRC LIVE , , 2002

//

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Proxy, Cache Miss / Cache Hit (Proxy): . .

Cache Miss / Cache Hit: http://www.cdnetworks.com/Media Acceleration.jpg , , 1) Cache Miss , www.cdnetworks.com Media Acceleration.jpg .

2) Cache Hit , . Hits . Hit Ratio . | NRC LIVE , , 2002

www.cdnetworks.comwww.daum.netwww.naver.com

Cache HitCache Miss

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Freshness / Validation checkFreshness check: Freshness . (Expiration time) HTTP max-age Expires . max age=86,400 (24) 24 Fresh . (Cache Hit)

(Validation) check: Hit Fresh . 1) 304 Not Modified , 2) . | NRC LIVE , , 2002

www.cdnetworks.comwww.daum.netwww.naver.com5. Update4. Response

3. Validation check2. Freshness check1. Cache Hit

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2. CDN Overview

Content Delivery Network (CDN Content Delivery Network): ( ) . (ISP Internet Service Provider) , .

CDN . CDN , (, , ), ( , , ), (, ), , .

(CP Content Provider) CDN , , CDN ISP . (Performance) (Service Availability) CDN (Origin server) .

CDN DoS . CDN Vendor P2P . (peer-user-owned) . | ,

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First mile, Middle mile and Last mile (IDC Internet Data Center) (ISP)

ISP

ISP

OriginWeb server(IDC)ISP

Local ISP

Internet Middle MileEnd user

Last MileMiddle MileFirst MileEnd userEnd userEnd user

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Middle mile problem

Origin Server Customer web site

End UserLast MileMiddle MileFirst MileSame ISP/LocationLow latencyLow BandwidthSame Data Center/ISPLow latencyLow BandwidthBad RoutingNetwork FailureLong distance

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Middle Mile problem without CDNCDN (CP) : , . . .

(ISP) : ISP , ISP IXP (Internet eXchange Provider) , ISP ISP IXP . ISP .

(End user) : , End-to-End delay (RTT Round Trip Time) . , YouTube , .

, , . | , CDN

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Solution for Middle mile problem (CDN)CDN . (CP) : , ( (Geographical Redundancy) ), , .

(ISP) : CDN ISP IXP , (Middle-Mile) , ISP - . ISP CDN . (. LGU+ YouTube )

(End user) : , End-to-End delay , . - Congestion . | , CDN

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Without CDN vs With CDN

(Origin server)

(Origin server)One Central web serverMany Cache servers

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3. Caching technology

Static and Dynamic Caching , CDN Origin Server ( ) (. Web object, , , ) (Caching) . .

Static Caching Origin Server . . (100% Cache hit)

Dynamic Caching . (Cache Miss) , Origin Server . (Caching) . (Cache Hit) (TTL - Time To Live) , Origin Server Freshness . | , CDN ADN

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Request RoutingRequest Routing Request (. ) CDN Request Router . Request Router DNS Redirection .

origin.example.com example.com DNS CNAME csp123.cdn.kt.com (5, 6)

Local DNS Request Router DNS Query Host Name = csp123.cdn.kt.com IP (7)

Request Router 1) Local DNS IP 2) , IP return (8, 9)

Request / (11, 12) | , CDN Request Routing

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Global Server Load BalancingGSLB (Global Server Load Balancing) GSLB (. ) , (Availability) . GSLB .GSLB SLB (Server Load Balancing) , SLB L4 , GSLB . | , Enterprise GSLB

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GSLB Basic OperationGSLB www.example.com Local DNS Query , Root DNS, .com DNS GSLB www.example.com DNS Query .GSLB DNS Proxy , DNS Query example.com DNS .example.com DNS www.example.com IP (SLB virtual IP) 1.1.1.1 2.2.2.2 GSLB . (TTL=300 )GSLB / (GSLB Policy) 1.1.1.1 2.2.2.2 .GSLB IP 1.1.1.1 Local DNS ,Local DNS () IP . www.example.com IP 1.1.1.1 destination SLB1 HTTP GET , SLB1 ( Health/Load ) 10.1.1.10 HTTP GET . | , Enterprise GSLB

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GSLB PolicyGSLB (GSLB Policy)Server Health check: / SLB Session & Network capacity threshold: Network Proximity: (Low Latency) Geographic Proximity: SLB Connection Load: Site Preference: Least Selected: Static Load Balancing: (Round Robin or Weighted Round Robin) | , Enterprise GSLB

/ 1 8 , 1 / 2 1 2 . enable/disable 1~8 .

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GSLB PolicyGSLB (GSLB Policy)Server Health Check: SLB ICMP(Internet Control Message Protocol), UDP, TCP, HTTP health check Application .Session & Network usage threshold: Server Health Check 1) session 2) Network usage (Over-loaded) . Session TCP UDP , Network usage SLB (bps) .Network Proximity: Session/Network usage , Network proximity . Network Proximity ( ) Low latency .Geographic Proximity: Network Proximity Local DNS ICMP , RTT , .SLB Connection Load: Geographic Proximity , SLB Connection Load . SLB Connection Load SLB TCP or UDP .Site Prefere

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