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Omrežja za distribucijo vsebin
Vidmar, Jernej (Author), Kos, Andrej (Mentor) More about this mentor... This link opens in a new window

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Abstract
Diplomska naloga opisuje delovanje omrežij za distribucijo vsebin. Ti se uporabljajo za fizično približanje spletne vsebine uporabnikom. To poteka tako, da se naredi kopija vsebin, ki jih uporabniki potrebujejo in se jo kopira na strežnik, ki je geografsko bližje uporabnikom. S tem se zmanjšajo zakasnitve pri dostopu do spletih vsebin. Posledično se zelo izboljša kakovost uporabniške izkušnje in pripomore k zmanjšanju prometa preko svetovnega spleta. Opis sistemov CDN se začne v 2. poglavju s predstavitvijo tipičnega modela CDN in zgodovino, ki je vodila do razvoja omrežij za distribucijo vsebine. V naslednjem poglavju so opisane različne metode, ki se uporabljajo pri optimalni postavitvi strežnikov, s katerih se predpomnjena vsebina streže uporabnikom. Treba je namreč najti primerno lokacijo za postavitev strežnika, ki bo lahko stregel čim več uporabnikom, s čim manjšimi zakasnitvami in s čim manjšimi stroški. V nadaljevanju je opisana distribucija vsebine z izvornega strežnika na robnega. Le-ta je različna glede na vrsto vsebine. Poznamo statično in dinamično vsebino ter pretočne medije. Poglavje 5 govori o usmerjanju zahtev po vsebini, ki jih sproži uporabnik, ko dostopa do spletne strani. Sistemi CDN uporabljajo različne mehanizme, ki zahteve usmerijo na najprimernejši robni strežnik, ki bo uporabniku dostavil vsebino v najkrajšem možnem času. V naslednjem poglavju je predstavljena strežba multimedijskih vsebin. Multimedijske vsebine so lahko na zahtevo ali pretočne. »Na zahtevo« so vnaprej posnete vsebine, ki se zlahka predpomnijo na robnih strežnikih. »Pretočne« pa so vsebine v živo, ki se jih ne da predpomniti, zato je za strežbo teh potrebno zagotoviti prenosno pot od vira pretoka do uporabnika. 7. poglavje predstavlja povezane CDN-je. Ponudniki CDN-storitev so namreč ugotovili, da se finančno zelo splača povezava s ponudniki CDN, ki imajo na voljo dodatna sredstva ali imajo večjo geografsko pokritost. Naslednje poglavje govori o internetni geolokaciji in njeni povezavi s sistemi CDN. Poglavje 9 opisuje, kakšen je dejanski učinek omrežij za distribucijo vsebin. Opravil sem meritve časa dostopanja do spletnih strani, ki se strežejo preko CDN in jih primerjal z meritvami tistih spletih strani, do katerih uporabniki dostopajo neposredno. Poleg tega sem primerjal tudi kakovost multimedijskih vsebin, ki se strežejo preko CDN s tistimi, ki se prenašajo direktno s strežnikov.

Language:Slovenian
Keywords:CDN, video na zahtevo, CMS-spletne strani, RTMP
Work type:Undergraduate thesis (m5)
Organization:FE - Faculty of Electrical Engineering
Year:2015
Views:638
Downloads:173
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Secondary language

Language:English
Title:Content Distribution Networks
Abstract:
The thesis describes the operation of Content Delivery Networks (CDN). These are used to physically move the web content closer to the web user. This is done by making a copy of the web content, that the users need, and moving it on a server that is geographically closer to the user. This reduces the delay when accessing the web content. As a result the Quality of Service (QoS) is greatly improved and it helps reduce traffic over the Internet. Description of CDNs begins in Chapter 2 with the presentation of a typcal CDN model and the history that has led to the development of network for the distribution of content. The following section describes the different methods used in optimal layout for servers where cached content is served to users. It is to find a suitable location for a server that can serve as many customers, minimizing delays and minimizing costs. Next Chapter describes the distribution of content from the source server to the edge server. It varies depending on the type of content. There are static and dynamic content and streaming media. Chapter 5 talks about directing requests for content, initiated by the user when accessing the website. CDN systems use a variety of mechanisms that direct requests to the most appropriate edge server that will deliver the content to the user as soon as possible. The next chapter presents the service of multimedia content. Multimedia content can be on-demand or streaming. On-demand is a pre-recorded content that can easily be cached on edge servers. Streaming content is a live recording which cannot be cached. To serve streaming content a transmission path from the source to the user has to be reserved. Chapter 7 presents interconnected CDNs - CDNI. CDN service providers have realised that connecting with the CDN providers who have additional resources available or have greater geographical coverage is financially very profitable. The next chapter talks about internet geolocation and its relation to the CDN systems. Chapter 9 describes the practical part of this thesis. The goal of the practical part is to examine what is the real impact of content distribution network. I measured the time to access the websites that are served via CDN and compared them with those measurements of websites to which users can access directly. In addition, I compared the quality of multimedia content that is served over CDN with those that are transmitted directly from the servers.

Keywords:CDN, video-on-demand, CMS websites, RTMP.

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