UPORABA PROTOKOLA MULTIPATH TCP V HIBRIDNEM DOSTOPOVNEM OMREŽJU

BOBNAR, GREGOR (author), Kos, Andrej (mentor)

Protokol za krmiljenje prenosa (TCP) je eden najbolj uporabljenih protokolov transportnega sloja. Pri uporabi sodobnih komunikacijskih naprav, ki imajo več omrežnih vmesnikov, pa se pokaže njegova omejenost. Vzpostavljena seja TCP se prekine, ko končna naprava zamenja omrežno povezljivost z enega vmesnika na drugega. Poleg tega pri napravah z več omrežnimi vmesniki nimamo možnosti, da bi znotraj ene seje izkoristili kapacitete obeh prenosnih poti. Namen naloge je predstaviti protokol Multipath TCP (MPTCP) in njegovo uporabo v hibridnem dostopovnem omrežju. Na začetku sem na kratko opisal zgodovino protokola TCP ter pojasnil vzroke za njegovo evolucijo, ki jo predstavlja protokol multipath TCP. Sledi podrobnejša analiza delovanja protokola in razlogi za njegovo vpeljavo. Multipath TCP je odprtokoden in možno ga je implementirati v Linux jedro. Navedel sem nekaj primerov, kjer ga že uporabljajo v komercialne namene. Predvsem me je zanimala izvedba hibridnega dostopa do interneta, kjer hkrati uporabimo širokopasovni dostop prek fiksnega omrežja digitalne naročniške zanke in mobilnega omrežja dolgoročne evolucije (LTE). Predstavil sem prednosti in slabosti take rešitve in jo podrobneje preveril v petem poglavju. V ta namen sem izvedel testno postavitev, kjer sem v jedro Linux operacijskega sistema implementiral MPTCP ter postavil vzpostavil dodaten proxy strežnik. Generiral sem internetni promet in spremljal, kako se ustvari več hkratnih povezav ter kako se porazdeli promet. Naknadno sem preveril, kaj se zgodi ob morebitnem izpadu ene povezave in kako dodatna omrežna povezava poveča prenosne hitrosti. Z meritvami sem določil spodnjo mejo jakosti signala LTE, da ne prihaja do prevelikega nihanja, ter predlagal uporabo zunanjih anten za stabilnejše delovanje. Opisal sem ovire, ki so se pojavile pri testiranju, in na koncu predstavil nekaj možnosti potencialne komercialne uporabe. Izkazalo se je, da je hibridni dostop zelo primerna rešitev za internetne ponudnike, ki želijo izboljšati svoje storitve predvsem na območjih s slabšimi internetnimi povezavami.

• Language: Slovenian
• Keywords: Multipath TCP, MPTCP, hibridni CPE, DSL dostop, LTE dostop, implementacija v Linux OS, redundanca
• Work type: Master's thesis
• Organization: FE - Faculty of Electrical Engineering
• Year: 2016
• PID: 20.500.12556/RUL-85154
• Publication date in RUL: 14.09.2016

Secondary language

• Language: English
• Title: USING THE MULTIPATH TCP PROTOCOL IN A HYBRID ACCESS NETWORK

Abstract

Transmission control protocol (TCP) is one of the most used protocols on the transport layer of ISO/OSI model. When using devices with multiple network interfaces we encounter its limits. Established TCP session fails when end device changes network connection from one interface to another. Moreover, these devices do not have the ability to transfer data over both interfaces at the same time to increase throughput. The objective of this thesis is to introduce the protocol Multipath TCP (MPTCP) and its usage in hybrid access network. First I described a TCP protocol and how it came to the idea of upgrading it to multipath TCP. I analyzed the principles of how it works and where or why it could be useful. Multipath TCP is an open-source protocol and it is possible to implement it into Linux kernel. There are already some innovative products that use it on the field. The main focus was the usage of MPTCP in hybrid access, where we used fixed broadband network and mobile network of long term evolution (LTE). In the fifth chapter I introduced benefits and drawbacks of this solution. Proof of concept was made with the implementation of MPTCP in the Linux kernel and setting up a proxy server. I generated internet traffic and observed the creation of subflows and usage of multiple network interfaces. MPTCP offers backup in case of failure of one network interface. Observation of hand-over was made with various Linux tools. With field measurements of LTE signal I evaluated what is the lowest signal strength that guarantees stable connection and proposed usage of external antennas. Challenges during testing were middleboxes that do not support MPTCP. In conclusion, hybrid access with multipath TCP is a very suitable solution for internet service providers that would like to offer advanced services in rural areas.

• Keywords: Multipath TCP, MPTCP, hybrid CPE, DSL access, LTE access, Linux OS implementation, redundancy