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Technical QoS, applications: IP, UMTS

Technical QoS, applications: IP, UMTS. Helsinki University of Technology S-72.2530 Acceptability and Quality of Service. 2.12.2008 Marko Rosberg. Why QoS is needed in IP level?. QoS-demanding IP aplications - Voice over IP (VoIP) ‏ - Internet Telephony - tele conferencing

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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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