{"69297":{"#nid":"69297","#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 compete for resources, resulting in the extinction of weaker competitors. A new computer model that describes the evolution of the Internet\u0027s architecture suggests something similar has happened among the layers of protocols that have survived -- and become extinct -- on the worldwide network.\u003C\/p\u003E\n\u003Cp\u003EUnderstanding this evolutionary process may help computer scientists as they develop protocols to help the Internet accommodate new uses and protect it from a wide range of threats. But the model suggests that unless the new Internet avoids such competition, it will evolve an hourglass shape much like today\u0027s Internet.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022To avoid the ossification effects we experience today in the network and transport layers of the Internet, architects of the future Internet need to increase the number of protocols in these middle layers, rather than just push these one- or two-protocol layers to a higher level in the architecture,\u0022 said Constantine Dovrolis, an associate professor in the 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 annual conference of the Special Interest Group on Data Communication, a special interest group of the Association for Computing Machinery. This 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, while the middle layers do not. The central transport layer contains two protocols and the network layer contains only one, creating an hourglass architecture.\n\u003C\/p\u003E\n\u003Cp\u003EDovrolis and graduate student Saamer Akhshabi created an evolutionary model called EvoArch to study the emergence of the Internet\u0027s hourglass structure. In the model, the architecture of the network changed with time as new protocols were created at different layers and existing protocols were removed as a result of competition with other protocols in the same layer.\n\u003C\/p\u003E\n\u003Cp\u003EEvoArch showed that even if future Internet architectures are not built in the shape of an hourglass initially, they will probably acquire that shape as they evolve. Through their simulations, Dovrolis and Akhshabi found that while the accuracy of the structure improved with time, the basic hourglass shape was always formed -- no matter what shape it started in.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022Even though EvoArch does not capture many practical aspects and protocol-specific or layer-specific details of the Internet architecture, the few parameters it is based on -- the generality of protocols at different layers, the competition between protocols at the same layer, and how new protocols are created -- reproduced the observed 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 hourglass shape. At the top, protocols are so specialized and selective in what underlying building blocks they use that they rarely compete with each other. When there is very little competition, the probability of 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 application-specific protocols are created over time, but few things die, causing the top of the hourglass to get wider over time,\u0022 said Dovrolis.\n\u003C\/p\u003E\n\u003Cp\u003EIn the higher layers, a new protocol can compete and replace an incumbent only if they provide very similar services. For example, services provided by the File Transfer Protocol (FTP) and HTTP overlapped in the application-specific layer. When HTTP became more valuable because of its own higher layer products -- applications such as web browsers -- FTP became extinct.\n\u003C\/p\u003E\n\u003Cp\u003EAt the bottom, each protocol serves as a general building block and shares many products in the layer above. For example, the Ethernet protocol in the data-link layer uses the coaxial cable, twisted pair and optical fiber technologies in the physical layer. But because the bottom layer protocols are used in an abundant way, none of them dominate, leading to a low probability of extinction at layers close to the bottom. \n\u003C\/p\u003E\n\u003Cp\u003EThe EvoArch model predicts the emergence of few powerful and old protocols in the middle layers, referred to as evolutionary kernels. The evolutionary kernels of the Internet architecture include IPv4 in the network layer, and TCP and the User Datagram Protocol (UDP) in the transport layer. These protocols provide a stable framework through which an always-expanding set of physical and data-link layer protocols, as well as new applications and services at the higher layers, can interoperate and grow. At the same time, however, those three kernel protocols 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 designing protocols that are largely non-overlapping in terms of services and functionality so that they do not compete with each other. The model suggests that protocols overlapping more than 70 percent of their functions start competing with each other.\n\u003C\/p\u003E\n\u003Cp\u003EWhen the researchers extended the EvoArch model to include a protocol quality factor -- which can capture protocol performance, extent of deployment, reliability or security -- the network grew at a slower pace, but continued to exhibit an hourglass shape. In contrast to the basic model, the quality factor affected the competition in the bottom layers and only high-quality protocols survived there. The model also showed that the kernel protocols in the waist of the hourglass were not necessarily the highest-quality protocols. \n\u003C\/p\u003E\n\u003Cp\u003E\u0022It is not true that the best protocols always win the competition,\u0022 noted Dovrolis. \u0022Often, the kernels of the architecture are lower-quality protocols that were created early and with just the right set of connections.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EResearchers are also using the EvoArch model to explore the emergence of hourglass architectures in other areas, such as metabolic and gene regulatory networks, the organization of the innate immune system, and in gene expression during development. \n\u003C\/p\u003E\n\u003Cp\u003E\u0022I believe there are similarities between the evolution of Internet protocol stacks and the evolution of some biological, technological and social systems, and we are currently using EvoArch to explore these other hourglass structures,\u0022 said Dovrolis.\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cem\u003EThis project is supported by the National Science Foundation (NSF) (Award No. 0831848). The content is solely the responsibility of the principal investigator and does not necessarily represent the official 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\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EA new computer model 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 ones became extinct.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"A new model describes how the Internet\u0027s architecture evolved."}],"uid":"27303","created_gmt":"2011-08-13 00:00:00","changed_gmt":"2016-10-08 03:09:55","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2011-08-13T00:00:00-04:00","iso_date":"2011-08-13T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"69298":{"id":"69298","type":"image","title":"Protocol stack","body":null,"created":"1449177252","gmt_created":"2015-12-03 21:14:12","changed":"1475894606","gmt_changed":"2016-10-08 02:43:26"},"69299":{"id":"69299","type":"image","title":"EvoArch Plot","body":null,"created":"1449177252","gmt_created":"2015-12-03 21:14:12","changed":"1475894606","gmt_changed":"2016-10-08 02:43:26"}},"media_ids":["69298","69299"],"related_links":[{"url":"http:\/\/www.scs.gatech.edu\/","title":"Georgia Tech School of Computer Science"},{"url":"http:\/\/www.scs.gatech.edu\/people\/constantine-dovrolis","title":"Constantine Dovrolis"}],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"153","name":"Computer Science\/Information Technology and Security"},{"id":"135","name":"Research"}],"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":[{"value":"\u003Cp\u003E\u003Cstrong\u003EJohn Toon\u003C\/strong\u003E\u003Cbr \/\u003EResearch News \u0026amp; Publications Office\u003Cbr \/\u003E\u003Ca href=\u0022http:\/\/www.gatech.edu\/contact\/index.html?id=jt7\u0022\u003EContact John Toon\u003C\/a\u003E\u003Cbr \/\u003E\u003Cstrong\u003E404-894-6986\u003C\/strong\u003E\u003C\/p\u003E","format":"limited_html"}],"email":["jtoon@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}