{"69301":{"#nid":"69301","#data":{"type":"news","title":"Study Shows How the Internet\u0027s Architecture Got its Hourglass Shape","body":[{"value":"\u003Cp\u003EIn the natural world, species that share the same ecosystem often \ncompete for resources, resulting in the extinction of weaker \ncompetitors. A new computer model that describes the evolution of the \nInternet\u0027s architecture suggests something similar has happened among \nthe layers of protocols that have survived -- and become extinct -- on \nthe worldwide network.\u003C\/p\u003E\n\u003Cp\u003EUnderstanding this evolutionary process may help computer scientists \nas they develop protocols to help the Internet accommodate new uses and \nprotect it from a wide range of threats. But the model suggests that \nunless the new Internet avoids such competition, it will evolve an \nhourglass shape much like today\u0027s Internet.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022To avoid the ossification effects we experience today in the network\n and transport layers of the Internet, architects of the future Internet\n need to increase the number of protocols in these middle layers, rather\n than just push these one- or two-protocol layers to a higher level in \nthe architecture,\u0022 said Constantine Dovrolis, an associate professor in \nthe School of Computer Science at the Georgia Institute of Technology. \n\u003C\/p\u003E\n\u003Cp\u003EThe research will be presented on Aug. 17, 2011 at SIGCOMM, the \nannual conference of the Special Interest Group on Data Communication, a\n special interest group of the Association for Computing Machinery. This\n research was supported by the National Science Foundation.\n\u003C\/p\u003E\n\u003Cp\u003EFrom top to bottom, the Internet architecture consists of six layers: \n\u003C\/p\u003E\n\u003Cp\u003E\u2022 Specific applications, such as Firefox;\u003Cbr \/\u003E\n\u2022 Application protocols, such as Hypertext Transfer Protocol (HTTP);\u003Cbr \/\u003E\n\u2022 Transport protocols, such as Transmission Control Protocol (TCP);\u003Cbr \/\u003E\n\u2022 Network protocols, such as Internet Protocol (IP);\u003Cbr \/\u003E\n\u2022 Data-link protocols, such as Ethernet; and\u003Cbr \/\u003E\n\u2022 Physical layer protocols, such as DSL.\n\u003C\/p\u003E\n\u003Cp\u003ELayers near the top and bottom contain many items, called protocols, \nwhile the middle layers do not. The central transport layer contains two\n protocols and the network layer contains only one, creating an \nhourglass architecture.\n\u003C\/p\u003E\n\u003Cp\u003EDovrolis and graduate student Saamer Akhshabi created an evolutionary\n model called EvoArch to study the emergence of the Internet\u0027s hourglass\n structure. In the model, the architecture of the network changed with \ntime as new protocols were created at different layers and existing \nprotocols were removed as a result of competition with other protocols \nin the same layer.\n\u003C\/p\u003E\n\u003Cp\u003EEvoArch showed that even if future Internet architectures are not \nbuilt in the shape of an hourglass initially, they will probably acquire\n that shape as they evolve. Through their simulations, Dovrolis and \nAkhshabi found that while the accuracy of the structure improved with \ntime, the basic hourglass shape was always formed -- no matter what \nshape it started in.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022Even though EvoArch does not capture many practical aspects and \nprotocol-specific or layer-specific details of the Internet \narchitecture, the few parameters it is based on -- the generality of \nprotocols at different layers, the competition between protocols at the \nsame layer, and how new protocols are created -- reproduced the observed\n hourglass structure and provided for a robust model,\u0022 said Dovrolis.\n\u003C\/p\u003E\n\u003Cp\u003EThe model revealed a plausible explanation for the Internet\u0027s \nhourglass shape. At the top, protocols are so specialized and selective \nin what underlying building blocks they use that they rarely compete \nwith each other. When there is very little competition, the probability \nof extinction for a protocol is close to zero. \n\u003C\/p\u003E\n\u003Cp\u003E\u0022In the top layers of the Internet, many new applications and \napplication-specific protocols are created over time, but few things \ndie, causing the top of the hourglass to get wider over time,\u0022 said \nDovrolis.\n\u003C\/p\u003E\n\u003Cp\u003EIn the higher layers, a new protocol can compete and replace an \nincumbent only if they provide very similar services. For example, \nservices provided by the File Transfer Protocol (FTP) and HTTP \noverlapped in the application-specific layer. When HTTP became more \nvaluable because of its own higher layer products -- applications such \nas web browsers -- FTP became extinct.\n\u003C\/p\u003E\n\u003Cp\u003EAt the bottom, each protocol serves as a general building block and \nshares many products in the layer above. For example, the Ethernet \nprotocol in the data-link layer uses the coaxial cable, twisted pair and\n optical fiber technologies in the physical layer. But because the \nbottom layer protocols are used in an abundant way, none of them \ndominate, leading to a low probability of extinction at layers close to \nthe bottom. \n\u003C\/p\u003E\n\u003Cp\u003EThe EvoArch model predicts the emergence of few powerful and old \nprotocols in the middle layers, referred to as evolutionary kernels. The\n evolutionary kernels of the Internet architecture include IPv4 in the \nnetwork layer, and TCP and the User Datagram Protocol (UDP) in the \ntransport layer. These protocols provide a stable framework through \nwhich an always-expanding set of physical and data-link layer protocols,\n as well as new applications and services at the higher layers, can \ninteroperate and grow. At the same time, however, those three kernel \nprotocols have been difficult to replace, or even modify significantly.\n\u003C\/p\u003E\n\u003Cp\u003ETo ensure more diversity in the middle layers, EvoArch suggests \ndesigning protocols that are largely non-overlapping in terms of \nservices and functionality so that they do not compete with each other. \nThe model suggests that protocols overlapping more than 70 percent of \ntheir functions start competing with each other.\n\u003C\/p\u003E\n\n\u003Cp\u003EWhen the researchers extended the EvoArch model to include a protocol\n quality factor -- which can capture protocol performance, extent of \ndeployment, reliability or security -- the network grew at a slower \npace, but continued to exhibit an hourglass shape. In contrast to the \nbasic model, the quality factor affected the competition in the bottom \nlayers and only high-quality protocols survived there. The model also \nshowed that the kernel protocols in the waist of the hourglass were not \nnecessarily the highest-quality protocols.\u003C\/p\u003E\n\u003Cp\u003E\u0022It is not true that the best protocols always win the competition,\u0022 \nnoted Dovrolis. \u0022Often, the kernels of the architecture are \nlower-quality protocols that were created early and with just the right \nset of connections.\u0022\u003C\/p\u003E\u003Cp\u003EResearchers are also using the EvoArch model to explore the emergence\n of hourglass architectures in other areas, such as metabolic and gene \nregulatory networks, the organization of the innate immune system, and \nin gene expression during development. \n\u003C\/p\u003E\n\u003Cp\u003E\u0022I believe there are similarities between the evolution of Internet \nprotocol stacks and the evolution of some biological, technological and \nsocial systems, and we are currently using EvoArch to explore these \nother hourglass structures,\u0022 said Dovrolis.\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cem\u003EThis project is supported by the National Science Foundation \n(NSF) (Award No. 0831848). The content is solely the responsibility of \nthe principal investigator and does not necessarily represent the \nofficial views of the NSF.\u003C\/em\u003E\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EResearch News \u0026amp; Publications Office\u003Cbr \/\u003E\nGeorgia Institute of Technology\u003Cbr \/\u003E\n75 Fifth Street, N.W., Suite 314\u003Cbr \/\u003E\nAtlanta, Georgia  30308  USA\n\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003E\n\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EMedia Relations Contacts\u003C\/strong\u003E: John Toon (404-894-6986)(\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E) or Abby Robinson (404-385-3364)(\u003Ca href=\u0022mailto:abby@innovate.gatech.edu\u0022\u003Eabby@innovate.gatech.edu\u003C\/a\u003E).\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: Abby Robinson\n\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EA new computer model designed by Constantine Dovrolis (\u003Cem\u003EComputer Science\u003C\/em\u003E) that describes the evolution of the Internet\u0027s architecture suggests a process similar to natural evolution took place to determine which protocols survived and which became extinct. \u003Cem\u003ESource: GT Research News\u003C\/em\u003E\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":"","uid":"27174","created_gmt":"2011-08-15 09:12:34","changed_gmt":"2016-10-08 03:09:55","author":"Mike Terrazas","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2011-08-15T00:00:00-04:00","iso_date":"2011-08-15T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"50659":{"id":"50659","type":"image","title":"Constantine Dovrolis","body":null,"created":"1449175421","gmt_created":"2015-12-03 20:43:41","changed":"1475894466","gmt_changed":"2016-10-08 02:41:06","alt":"Constantine Dovrolis","file":{"fid":"128787","name":"constantine-dovrolis.jpg","image_path":"\/sites\/default\/files\/images\/constantine-dovrolis_1.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/constantine-dovrolis_1.jpg","mime":"image\/jpeg","size":11583,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/constantine-dovrolis_1.jpg?itok=fVGIKhhn"}}},"media_ids":["50659"],"groups":[{"id":"47223","name":"College of Computing"}],"categories":[],"keywords":[{"id":"439","name":"computer"},{"id":"13398","name":"Constantine Dovrolis"},{"id":"13994","name":"Internet architecture"},{"id":"1385","name":"network"},{"id":"13995","name":"protocol"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[],"email":[],"slides":[],"orientation":[],"userdata":""}}}