Wireless networks - Lecture 30: QoS in WLAN/Mobile IP. The main topics covered in this chapter include: limitations of QoS in IEEE 802.11; overview of 802.11e; traffic categories; EDCF; HCF; Mobile IP; distributed coordination function (DCF); point coordination function (PCF);...
Wireless Networks Lecture 30 QoS in WLAN / Mobile IP Dr Ghalib A Shah Outlines Last lecture Limitations of QoS in IEEE 802.11 Overview of 802.11e Traffic Categories EDCF HCF Mobile IP ► ► ► ► ► Care-of-address, MIP Protocol (Discovery, Registration, Tunneling) Routing Inefficiencies MIPv6 Last Lecture Types of Attack Goals of 802.11 Security ► Access control, data integrity, confidentality WEP Protocol WEP Authentication Security flaws in original 802.11 ► Physical threat, impersonation, mutual authentication, dictionary attacks, DOS 802.1x Security ► AKM Operations with AS ► AKM operations with PSK IBSS Security model QoS Limitations of 802.11 DCF (Distributed Coordination Function) ► Only support best-effort services ► No guarantee in bandwidth, packet delay and jitter ► Throughput degradation in the heavy load PCF (Point Coordination Function) ► Inefficient central polling scheme ► Unpredictable beacon frame delay due to incompatible cooperation between CP and CFP modes ► Transmission time of the polled stations is unknown Overview of 802.11e Formed in Sep 1999 TheQoSbaseline document was approved in November 2000 The first draft was available in late 2001 Aim to support both IntServ and DiffServ New QoS mechanisms ► EDCF (Enhanced DCF) ► HCF (Hybrid Coordination Function) Backwardly compatible with the DCF and PCF QoS is realized by introducing traffic categories (TCs) MSDUs are delivered through multiple backoff instances running as virtual stations ► Each instance is parameterized with TC specific parameters • AIFS, CWmin, CWmax, Persistance factor (PF) ► For legacy DCF, AIFS=DIFS, PF=2, CWmin DIFS) which is shorter for audio and video traffic ► Audio =Video