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July 2000 doc.: IEEE 802.11-00/214 Implementation Options for the Distribution System in the 802.11 Wireless LAN Infrastructure Network Amre El-Hoiydi, CSEM, Switzerland IEEE ICC 2000 Submission Slide 1 Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 IEEE 802.11 • PHY – Frequency-Hopping / DSSS / Infra Red • MAC – Wireless Ethernet • Network Architecture – Ad Hoc Network – Infrastructure Network Submission Slide 2 Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Ad Hoc Network Submission Slide 3 Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Infrastructure Network Internet Portal Distribution System Access Point Access Point Access Point ESS Submission Slide 4 BSS Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Definitions • Basic Service Set: • Extended Service Set: • Distribution System: • Access Point: • Portal: Submission A wireless cell All wireless cells Glue between the BSS to form the ESS Connection DS - BSS Connection DS - Wired LAN Slide 5 Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Distribution System • • • • Several cells form a virtual single shared-medium Distribution system responsible of routing frames Distribution system transparent to LLC Portal + Access Points = MAC Bridge between the wired LAN and the cells LLC 802.2 LLC 802.2 Distribution System MAC 802.11 MAC 802.11 station Submission MAC 802.3 portal access point Slide 6 MAC 802.3 desktop computer Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Operation: Traffic Data frame from the station to the access point (In the FrameControl: ToDS bit is 1, FromDS bit is 0): Frame Address 1 Address 2 Control BSSID (=MAC AP 1) SA = MAC Station 1 Address 3 Sequ DA = MAC Station 3 Control Address 4 Not Used Frame Body 0-2312 octets FCS Data frame from the access point to the station (In the FrameControl: ToDS bit is 0, FromDS bit is 1): Frame Address 1 Address 2 Address 3 Sequ Control DA = MAC Station 3 BSSID (=MAC AP 3) SA = MAC Station 1 Control • No direct traffic between stations Submission Address 4 Not Used Access Point Access Point Slide 7 Frame Body 0-2312 octets FCS Access Point Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Operation: Roaming Access Point Access Point Access Point Association request Reassociation request Association response Reassociation response 1 2 • Association protocol gives to the distribution system the necessary information to perform the mobility management Submission Slide 8 Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Logical Services Internet • Station Service Desktop Comp – Authentication, Gateway – Encryption, Ethernet – MSDU Delivery Portal • Distribution System Service – Association, integr DSS distrib Distribution System Medium DSS AP1 distrib assoc SS – Distribution (unspecified), DSS AP2 distrib assoc SS DSS AP3 distrib assoc SS – Integration (unspecified) SS STA1 Submission SS STA2 Slide 9 SS STA3 Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Implementation Options for the Distribution System • Choice of a distribution transport protocol and addressing – LLC Type 1 (connectionless) transport, MAC addressing or – UDP/IP transport, IP layer addressing • Choice of a mobility management signalling protocol Submission Slide 10 Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Overview of the discussed options • MAC Layer Addressing – Option 1: Separated Access Points and Portals – Option 2: Joined Access Point and Portals – Option 3: MAC Bridges • Network Layer Addressing – Option 4: Network Layer Addressing Submission Slide 11 Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Option 1: Separated AP / Portals LLC 802.2 LLC 802.2 assoc distrib MAC 802.11 MAC 802.11 station assoc distrib LLC 802.2 LLC 802.2 MAC 802.3 MAC 802.3 access point MAC 802.11 MAC 802.11 access point station LLC 802.2 distribution system medium distrib integr LLC 802.2 MAC 802.3 MAC 802.3 MAC 802.3 wired LAN portal Submission Slide 12 desktop computer Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Option 1: Transport plane • Max size of a 802.11 MSDU = 2304 Bytes • Max size of the payload in 802.3 = 1492 Bytes • Segmentation needed • Connection protocol needed to avoid mixing segments from different sources Submission Slide 13 Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Option 1: Signalling • Goal of the mobility management signalling is that each access point or portal knows through which access point or portal a given MAC address can be reached. • What access point correspond to what MAC address ? • It is proposed to use a dynamic route resolution protocol similar to the Ethernet Address Resolution Protocol (ARP, RCF826) Submission Slide 14 Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Option 1: Route Resolution Submission Slide 15 Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Option 1: Handover Submission Slide 16 Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Option 2: Joined AP / Portals LLC 802.2 LLC 802.2 assoc MAC 802.11 integr integr distrib MAC 802.11 MAC 802.11 distrib LLC LLC MAC 802.3 station assoc MAC 802.11 MAC 802.3 access point / portal access point / portal station LLC 802.2 wired LAN and distribution system medium Submission Slide 17 MAC 802.3 desktop computer Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Option 2 versus Option 1 • The mobility management signalling protocol is identical as in option 1 • Having the portal functions in the access points prevents the need of forwarding over the distribution medium the traffic to/from the wired LAN Submission Slide 18 Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Option 3: MAC Bridge • If the MSDU maximum size in 802.11 is reduced from 2304 to 1476, each access point can be a filtering bridge • The access point will forward into the cell the frames destined to associated stations • No need of mobility management signalling • Association protocol is sufficient to give enough information for the filtering task Submission Slide 19 Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Option 3: Network Architecture LLC 802.2 LLC 802.2 assoc integr integr assoc MAC 802.11 MAC 802.11 station MAC 802.3 MAC 802.3 MAC 802.11 MAC 802.11 Access Point MAC Bridge Access Point MAC Bridge station LLC 802.2 wired LAN MAC 802.3 desktop computer Submission Slide 20 Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Option 4: Network Layer Addressing LLC 802.2 LLC 802.2 assoc distrib MAC 802.11 assoc distrib UDP/IP MAC 802.11 station UDP/IP LLC 802.2 LLC 802.2 MAC 802.3 MAC 802.3 access point subnet 192.168.120.0 station subnet 172.16.100.0 subnet 192.168.121.0 distribution system medium LLC 802.2 distrib integr MAC 802.3 UDP/IP IP Router LLC 802.2 MAC 802.3 MAC 802.3 subnet 192.168.122.0 portal Submission MAC 802.11 access point IP Router subnet 172.16.100.0 MAC 802.11 Slide 21 wired LAN desktop computer Amre El-Hoiydi, CSEM subnet 172.16.100.0 July 2000 doc.: IEEE 802.11-00/214 Option 4: Signalling • Access points not linked through a broadcast medium anymore • RoutingRequest and RoutingIndication messages cannot be broadcast anymore • It is proposed to use a dynamic address resolution protocol similar to the Address Resolution Protocol over ATM (ARP over ATM, RCF2225) • Each access point must be given the IP address of the server Submission Slide 22 Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Option 4: Route Resolution Submission Slide 23 Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Option 4: Handover Submission Slide 24 Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Summary Option Addressing Comments 1 Separated AP / Portal MAC 2 Joined AP / Portal MAC 3 MAC Bridge MAC 4 Network Layer Addressing Submission IP Routing resolution signalling uses broadcast messages - Wired LAN traffic repeated Routing resolution signalling uses broadcast messages + Wired LAN traffic not repeated + No signalling - Maximum 802.11 MSDU size not standard Solution used today in the industry Routing resolution signalling uses a central server + Flexibility in backbone network architecture - Transmission delay can be high Slide 25 Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Standardisation • 802.11 TGf Task Group has started the work on IAPP • One IAPP proposal made in 1996 – Uses IP layer addressing – Transmission of unsolicited “announce” messages • Schedule – May 2000, fist meeting held – July 2000, proposals – Sept 2000, first draft Submission Slide 26 Amre El-Hoiydi, CSEM July 2000 doc.: IEEE 802.11-00/214 Conclusion • MAC bridge solution simple but limited • Should be augmented with a network layer IAPP • Remaining points to study • impact of lost messages • impact of crossed handover messages (RoutingIndication) • comparison between schemes based on requests or on unsolicited messages Submission Slide 27 Amre El-Hoiydi, CSEM