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Technical QoS, applications: IP, UMTS

This document explores the essentiality of Quality of Service (QoS) in IP networks, focusing on applications such as Voice over IP (VoIP), internet telephony, and e-commerce. It discusses the challenges faced due to varying network loads and the importance of QoS in managing different application requirements. The paper examines various methods for implementing QoS, including traffic modeling, admission control, and scheduling. Furthermore, it covers QoS in UMTS (3G cellular networks), explaining the roles of resource management and specific QoS parameters necessary for efficient data transmission.

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Technical QoS, applications: IP, UMTS

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  1. Technical QoS, applications: IP, UMTS Helsinki University of Technology S-72.2530 Acceptability and Quality of Service 2.12.2008 Marko Rosberg

  2. Why QoS is needed in IP level? • QoS-demanding IP aplications • - Voice over IP (VoIP)‏ • - Internet Telephony • - tele conferencing • - virtual private networks (VPN)‏ • - e-commerce

  3. Challenges • - Network load may vary much • - Over-provisioning in wired connections • - IP is connectionless protocol • - Very different kinds of requirements from different applications (e.g. VoIP datarates are quite small but latency should be less than 100ms)‏ • - Requires changes to Internet backbones • - Different kind of technologies used • - 3G, WLAN, ADSL, Optical fibers

  4. Methods for adding QoS control • - Traffic modeling • - Admission Control • - Shaping and Policing • - Signaling and Resource Management • - Queuing and Scheduling • - Cognestion control and Queue Management • - QoS Routing • - QoS Policy Management • - Pricing

  5. How is it made in IPv4? • - IP V4 header includes Type of Service (ToS) field • - Defined 1981 in RFC791 • - Length 8bit • - The major choice is a three way tradeoff between low-delay,high-reliability, and high-throughput • - The use of the Delay, Throughput, and Reliability indications may increase the cost

  6. How is it made in IPv4? cont. • - ToS field consists of the following bits • Bits 0-2: Precedence. • Bit 3: 0 = Normal Delay, 1 = Low Delay. • Bits 4: 0 = Normal Throughput, 1 = High Throughput. • Bits 5: 0 = Normal Relibility, 1 = High Reliability. • Bit 6-7: Reserved for Future Use. Precedence 111 - Network Control 110 - Internetwork Control 101 - CRITIC/ECP 100 - Flash Override 011 - Flash 010 - Immediate 001 - Priority 000 - Routine • - The type of service is used to specify the treatment of the datagram during its transmission through the internet system.

  7. IPv4 in practice • - ToS field has not been widely implemented • - Much research focused on how these bits could be used • - Bits have been redefined, most recently through DiffServ working group • - ToS field is now used for DiffServ and ECN

  8. What is DiffServ ? • - DiffServ stands for Differentiated Services • - Defined 1998 in RFC 2475 • - It operates on principle of traffic classification • - Each router is configured to differentiate traffic based on its class • - It can be used to provide low latency traffic for voice and video services while providing best-effort traffic for non critical traffic

  9. What is ECN? • - ECN stands for Explicit Congestion Notification • - Defined 2001 in RFC 3168 • - Uses DiffServ field • - allows end-to-end notification of network congestion without dropping packets • - It's an optional feature (only used when both endpoints signal that they want to use it)‏ • - only effective in combination with an Active Queue Management (AQM) policy

  10. QoS control in IPv6 • - Header includes 20 bits long flow label for QoS management • - Basics of Flow Label is specified in RFC 3697 • - Published in 2004 • - The specific properties and utility of this header field are not well defined at present • - Enables classification of packets belonging to a specific flow • - Routers priorizes IP packets based on flow type

  11. QoS in UMTS • - W-CDMA (UMTS) (Wideband Code Division Multiple Access) is a type of 3G cellular network • - QoS control used in different levels of OSI-Model • - Optimum use of spectrum is important • - Overprovisioning is very expensive alternative

  12. QoS in UMTS cont. Radio QoS support - Covers all traffic types - Dedicated vs. shared channels - Soft handover - Real-time handover Radio network QoS/Core network interface - Connection oriented - Differentiated Services can be used at IP layer - ATM-based transmission Core network QoS - Differentiated Services proposed PDP context approach UMTS-specific QoS parameters Flexible renegotiation of QoS - Flow specifications at GGSN - UMTS-specific QoS parameters

  13. QoS in UMTS cont. • - Most of the QoS control is done at the bearer level • - Used methods: • Admission control • Bearer service manager • Resource manager • Traffic conditioner • Packet classifier

  14. Admission control & Bearer service manager • Admission Control • - maintains information about the allocated and free resources • - allocates and frees resources based on QoS parameter values • Bearer service manager • - co-ordinates signal plane to establish, modify and maintain the particular bearer service • - consults admission control and translates QoS attributes for local bearer

  15. Resource Manager & Traffic Controller • Resource Manager • - Responsible for managing access to resources in accordance with particular bearer service • - Uses QoS parameters for scheduling, bandwith management and power control • Traffic Conditioner • - Traffic shaping and policing • - Ensures uplink in MS* and downlink in GGSN** • - The result TC is a packet with appropiate QoS indication e.g. IP packet *MS = Mobile Station **GGSN = Gateway GPRS Support Node

  16. Packet Classifier • - Classifies packets to bearer service based on QoS attributes • - Four different traffic classes • - Conversational class • real time traffic e.g. Video telephony • - Streaming class • media streaming traffic e.g. Video download • - Interactive class • services reguiring assure throughput e.g. Interactive web • - Background class services • best-effort data e.g. Downloading files or email

  17. Critics • - There are many different ways for adding QoS to IP • It's allmost impossible to have connection on the Internet, where every node between the endpoints supports QoS method that you are using. • - There have been mutch articles of unsatisfied customers using UMTS (what went wrong?)‏

  18. Thank you for listening!! • Sources: 1) Wikipedia IP, http://en.wikipedia.org/wiki/Ip 2) Wikipedia UMTS, http://en.wikipedia.org/wiki/Umts 3) Rajeev Koodli and Mikko Puuskari, Nokia Research Center, Supporting Packet-Data QoS in Next-Generation Cellular Networks, IEEE 2001 4) JOHN SOLDATOS et.al. , ON THE BUILDING BLOCKS OF QUALITY OF SERVICE IN HETEROGENEOUS IP NETWORKS, IEEE 2005, http://www.comsoc.org/pubs/surveys 5) RFC791, Internet Protocol, 1981, http://tools.ietf.org/html/rfc791 6) RFC3697 - IPv6 Flow Label Specification, 2004, http://www.faqs.org/rfcs/rfc3697.html

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