May 2004 doc.: IEEE 802.11-04/629r1 May 2004 The Nature of an ESS Darwin Engwer, Nortel Networks Bob O’Hara, Airespace dengwer@nortelnetworks.com bob@airespace.com Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace

Further thoughts on ESS (triggered by submission 11-04-0614-00) May 2004 Further thoughts on ESS (triggered by submission 11-04-0614-00) Doc 614 [1] cites a number quotes directly from the standard wrt the definition of an ESS. Strictly interpreted these existing definitions constrain the implementation options as cited in doc 614 However, other logical (abstract) views are possible, which have in fact allowed vendors to construct functional WLANs within the constraints imposed by existing definitions. First, a diagram from doc 614 ... Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace

AP + DS + Portal Portal Distribution System May 2004 Slide 6 from [1] doc 11-04-614-00 AP + DS + Portal HOST Router 802.3 network Portal Distribution System AP AP AP STA Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace

But real world implementations (to date) look like this ... May 2004 But real world implementations (to date) look like this ... Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace

Real World AP Devices May 2004 AP Device AP Device HOST Router 802.3 network 802.3 L2 Hub or Switch WM Portal Integration Distribution System AP Device WM Portal Integration Distribution System AP Device STA STA STA Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace

May 2004 doc.: IEEE 802.11-04/629r1 May 2004 Real World AP Review In that common real world AP and WLAN implementation, the mini-DSs and portals in each AP combined with the 802.3 L2 network can be considered as forming a single logical Distribution System and Portal, since those logical components meet all the criteria described in 802.11-1999 Clause 5. “5.2.2 … The IEEE 802.11 LAN architecture is specified independently of the physical characteristics of any specific implementation.” … The DS enables mobile device support by providing the logical services necessary to handle address to destination mapping and seamless integration of multiple BSSs.” Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace

Logical DS and Portal Distribution System Portal May 2004 AP Device HOST Router 802.3 network 802.3 L2 Hub or Switch Portal Distribution System WM Portal Integration Distribution System AP Device WM Portal Integration Distribution System AP Device A single logical portal is indistinguishable from multiple physical portals. STA STA STA Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace

May 2004 Logical DS and Portal There is no disagreement between the Logical DS and Portal model and the formal definitions provided in 802.11-1999 Clause 5. Consider: “5.2.2.1 The key concept is that the ESS network appears the same to an LLC layer as an IBSS network. Stations within an ESS may communicate and mobile stations may move from one BSS to another (within the same ESS) transparently to LLC.” Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace

L2 Connectivity with a Logical DS and Portal May 2004 L2 Connectivity with a Logical DS and Portal HOST Router 802.3 network 802.3 L2 Hub or Switch Portal Distribution System WM Portal Integration Distribution System AP Device WM Portal Integration Distribution System AP Device STA STA STA L2 link L2 link Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace

May 2004 Extent of the ESS Hence, the ESS can span all the APs in such a network. Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace

ESS with a Logical DS and Portal May 2004 ESS with a Logical DS and Portal HOST Router 802.3 network 802.3 L2 Hub or Switch Portal Distribution System WM Portal Integration Distribution System AP Device WM Portal Integration Distribution System AP Device STA STA STA ESS L2 link ESS L2 link Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace

What if the network includes a router? May 2004 What if the network includes a router? Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace

L2 Connectivity with a Logical DS and Portal using a Router May 2004 L2 Connectivity with a Logical DS and Portal using a Router HOST Router 802.3 network Distribution System 802.3 L2 Hub or Switch Portal 802.3 L2 Hub or Switch Portal WM Portal Integration Distribution System AP Device WM Portal Integration Distribution System AP Device STA STA STA L2 link L2 link Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace

L2 Connectivity thru a Distribution System that includes a Router May 2004 doc.: IEEE 802.11-04/629r1 May 2004 L2 Connectivity thru a Distribution System that includes a Router At first look it appears as if the two STAs on opposite sides of the router do not have L2 Connectivity. However, the DS (or some other component in the network) can arrange this to be true. e.g. the mini-DS in one AP can transport the MSDU to the mini-DS in the AP that is on the other side of the router. The second AP can then deliver the MSDU to the mobile STA. To the mobile STAs it appears as if they have L2 connectivity. e.g. A consistent VLAN can be set up on both sides of the router, so that packets on that VLAN are switched across the router. In fact, this is a common deployment scenario today. Again, to the mobile STAs it appears as if they have L2 connectivity. Clause 5.2.2.1: “The key concept is that the ESS network appears the same to an LLC layer as an IBSS network. Stations within an ESS may communicate and mobile stations may move from one BSS to another (within the same ESS) transparently to LLC.” Note that the cited clause refers to “transparently to LLC”. That is the criteria, NOT IP connectivity between the two STAs. IP connectivity between the two STAs may be compromised at times because the IP stack (knowing the two IP addresses to be on different subnets) will re-address the packets at layer 2 (to instead send the packet to the gateway). This has no bearing on whether another network application, using the 802.11 MAC-SAP interface can send 802.11 messages (tuples) from one STA to another. Clause 6.1.1 and 6.2.1.1.2 define the MAC data service. The MA-UNITDATA.request primitive parameters [the tuple] are (SA, DA, data, …). The data parameter is the actual MSDU, although we often use the shorthand notation of MSDU to refer to the entire tuple (t). Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace

ESS with a Logical DS and Portal using a Router May 2004 ESS with a Logical DS and Portal using a Router Hence, the ESS concept can apply to WLAN deployments that rely on a logical DS/ logical portal(s) construct, even when using a router. Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace

ESS with a Logical DS and Portal using a Router May 2004 ESS with a Logical DS and Portal using a Router HOST Router 802.3 network Distribution System 802.3 L2 Hub or Switch Portal 802.3 L2 Hub or Switch Portal WM Portal Integration Distribution System AP Device WM Portal Integration Distribution System AP Device STA STA STA ESS L2 link ESS L2 link Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace

ESS Summary BSSs with the same SSID may be part of the same ESS. No scenarios are [necessarily] excluded. The 802.11-1999 definition of an ESS is somewhat broad and flexible. Therefore, TGr may need to specify and explicitly define the BSS-transition cases that are in-scope and out-of-scope. i.e. If TGr wants something more precise than ESS, then need to specify that. Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace

References: [1] 11-04-0614-00-frfh-what-ess.ppt May 2004 References: [1] 11-04-0614-00-frfh-what-ess.ppt [2] 11-04-0500-01-0mes-need-clarification-definition-ess-mesh.ppt Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace

The End May 2004 doc.: IEEE 802.11-04/629r1 May 2004 Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace Darwin Engwer, Nortel Networks; Bob O'Hara, Airespace