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Sidevõrgud IRT 0020 loeng 7 30. okt. 2006

Sidevõrgud IRT 0020 loeng 7 30. okt. 2006. Avo Ots telekommunikatsiooni õppetool raadio- ja sidetehnika instituut avots@lr.ttu.ee. Market. End-Users. Content and Service Providers. Service operators/ Telecommunications Networking Solutions. Physical Telecommunication Network. QoS.

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Sidevõrgud IRT 0020 loeng 7 30. okt. 2006

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  1. SidevõrgudIRT 0020loeng 7 30. okt. 2006 Avo Ots telekommunikatsiooni õppetoolraadio- ja sidetehnika instituut avots@lr.ttu.ee

  2. Market End-Users Content and Service Providers Service operators/ Telecommunications Networking Solutions Physical Telecommunication Network

  3. QoS • Pakettvõrkudes liikluse korralduse (traffic engineering) mõiste “garanteeritud teenuse kvaliteet” (QoS, Quality of Service) tähendab tõenäosuslikku hinnangut, et sidevõrk jälgib liikluslepet. • Paljudel juhtudel kasutatakse QoS tõenäosusena, et pakett läbib võrku saatjast vastuvõtjani oma ettemääratud ajavahemiku jooksul.

  4. Teenusekvaliteedi aspektid QoS – Quality of Service ITU-T E.800 Recommendation

  5. Teenusekvaliteedi aspektid (2) QoS Teenuse Kättesaadavus (Accessibility) Teenuse Püsivus (Retainability) Teenuse Terviklikus (Integrity) QoS parameetrid QoS parameetrid QoS parameetrid

  6. QoS rules • QoS doesn't create bandwidth --it just determines who will get poor service at congestion points. • The most important QoS question is: how many "busy" signals constitute success for your network? • Given a busy signal, users will want to proceed anyway. • Network Managers will not trust end systems. • Biggest need is on WAN links, where it’s hardest to do! (scaling, settlements, signalling interoperability). • Multiplexing priorities on a channel improves efficiency at the cost of certainty.

  7. Link Scheduling: FIFO • First-in first-out scheduling • Simple to implement • But, restrictive in providing guarantees • Example: two kinds of traffic • Video conferencing needs high bandwidth and low delay • E.g., 1 Mbps and 100 msec delay • E-mail transfers are not that sensitive about delay • Cannot admit much e-mail traffic • Since it will interfere with the video conference traffic

  8. Link Scheduling: Strict Priority • Strict priority • Multiple levels of priority • Always transmit high-priority traffic, when present • .. and force the lower priority traffic to wait • Isolation for the high-priority traffic • Almost like it has a dedicated link • Except for the (small) delay for packet transmission • High-priority packet arrives during transmission of low-priority • Router completes sending the low-priority traffic first

  9. 50% red, 25% blue, 25% green Link Scheduling: Weighted Fairness • Limitations of strict priority • Lower priority queues may starve for long periods • … even if the high-priority traffic can afford to wait • Weighted fair scheduling • Assign each queue a fraction of the link bandwidth • Rotate across the queues on a small time scale • Send extra traffic from one queue if others are idle

  10. IP Packet Structure 4-bit Header Length 8-bit Type of Service (TOS) 16-bitTotal Length (Bytes) 4-bit Version 3-bit Flags 16-bit Identification 13-bit Fragment Offset 20-byte Header 8-bit Time to Live (TTL) 8-bitProtocol 16-bit Header Checksum 32-bit Source IP Address 32-bit Destination IP Address Options (if any) Payload

  11. TCP Header 16-bit destination port number 16-bit source port number 32-bit sequence number 20-byte Header 32-bit acknowledgement number U R G A C K P S H R S T S Y N F I N 4-bit header length 16-bit window size 16-bit urgent pointer 16-bit TCP checksum Options (if any) Payload

  12. Teenusekvaliteedi aspektid (3) • Iga teenuse jaoks oma nõuded • QoS profiil • Erinevad teenusekvaliteedi tasemed vastavalt nõuetele

  13. Näidsvõrgud • Coexistence of heterogeneous networks • Home networks, WLAN, 2G/3G, Campus-wide, satellite, … • The development of multimode handsets is a major challenge • Currently discussed standards fall short • Tomorrow user’s will expect the technology structure to “disappear” and be of no concern • Network architecture designed by IST project Daidalos • Provide seamless services accessible anytime anywhere across heterogeneous technologies • Enhanced Mobile IPv6 platform for mobility and QoS • Support for optimized mobility • Integration with QoS resource management

  14. Mobile Terminal Technologies IPv6++/MIPv6/Multicast Terminal Intelligence QoS User GUI FHO CARD IIS Handover QoSC MTC IAL QoSAL MBMS TD-CDMA WLAN WiMAX UDLR DVB-T

  15. Access Router / Access Point Technologies FHO CT D&M Terminal Intelligence IPv6++/MIPv6/ PIM Network Intelligence AM QoS CARD PA MM QoSM Handover QoSAL ENC MBMS TD-CDMA WLAN WiMAX UDLR DVB-T

  16. Handover • Mobile Initiated Handover • Network Initiated Handover • Triggered • At startup • Upon losing signal • Accounts for • user preferences • candidate APs load (QoS) • signal strengths • Triggered by • Overloaded AP (QoS) • losing signal • Accounts for • signal strengths of MTs • APs load (QoS)

  17. Wi-Fi Alliance Roadmap[Amer Hassan, Microsoft, jaanuar 2005] 802.11k 802.11j 802.11e 2004 2005 2006 Q1 Q2 Q3 Q4 Baseline Security QoS Applications 802.11h+d Extended EAP SimpleConfig WMM Scheduled Access WMM Power Save CE Phase1 Public Access Voice/Wi-Fi WCC CE Phase2

  18. QoS vajadus • QoS vajadus esmases tähenduses tuleneb video ja suure edastuskiirusega (mobiilsetest) andmesessioonidest • Lõplikult kavatsetakse realiseerida standardina IEEE 802.11n, vahevariant realiseeriti standardina IEEE 802.11e, mida toetab Proximi AP-4000.

  19. Roadmap – WLAN

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