3. doc.: 11-04-0500-00-0mes
Submission
7 May 2004
Tricci So
Slide 3
What is Basic Service Set (BSS)?
However, ESS Mesh is more than just supporting BSSs !!!
Bridge/Switch/Router
AP
MN/STA
BSS
A set of stations (MN/STA)
controlled by a single Access
Point (AP) operating in an
infrastructure mode.
•ANSI/IEEE Std 802.11, 1999
Edition, page 3 – 3.7: A set of
stations controlled by a single
coordination function.
• ANSI/IEEE Std 802.11, 1999
Edition, page 4 – 3.13:
Coordination Function: The logical
function that determines when a
station operating within a basic
service set (BSS) is permitted to
transmit and may be able to
receive protocol data units (PDUs)
via the wireless medium (WM).
4. doc.: 11-04-0500-00-0mes
Submission
7 May 2004
Tricci So
Slide 4
What is a Distribution System (DS)?
•ANSI/IEEE Std 802.11, 1999 Edition, page 4 – 3.20: A system used to interconnect a set of Basic
Service Sets (BSSs) and integrated Local Areas Networks (LANs) to create an Extended Service Set
(ESS).
• ANSI/IEEE Std 802.11, 1999 Edition, page 11 – 5.2.2: The DS enables mobile device support by
providing the logical services necessary to handle address to destination mapping and seamless
integration of multiple BSSs . . . . .
An Access Point (AP) is a STA that provides access to the DS by providing DS services in addition
to acting as a STA. . . => AP = providing DS services + STA
Data move between a BSS and the DS via an AP. Note that ALL APs are ALSO STAs; thus they are
addressable entities. The addresses used by an AP for communication on the WM and on the DSM
are NOT necessarily the same . . .
• ANSI/IEEE Std 802.11, 1999 Edition, page 14 – 5.3: The IEEE 802.11 architecture allows for the
possibility that the DS may NOT be identical to an existing wired LAN. A DS may be created from
many different technologies including current IEEE 802 wired LANs. IEEE 802.11 does NOT
constrain the DS to be either DATA or NETWORK layer based. Nor does IEEE 802.11 constrain a
DS to be either centralized or distributed in nature.
What is WDS? WDS = Wireless Distribution System
5. doc.: 11-04-0500-00-0mes
Submission
7 May 2004
Tricci So
Slide 5
What is 802.11 infrastructure?
•ANSI/IEEE Std 802.11, 1999 Edition, page 5 – 3.28: The infrastructure
includes the distribution system medium (DSM), access point (AP), and
portal entities. It is also the logical location of distribution and integration
service functions of an Extended Service Set (ESS). An infrastructure
contains one or more APs and zero or more portals in addition to the
Distribution System (DS).
What is 802.11 Independent Basic Service Set
(IBSS)?
•ANSI/IEEE Std 802.11, 1999 Edition, page 5 – 3.27: A BSS that forms a self-
contained network, and is which no access to a Distribution System (DS) is
available.
6. doc.: 11-04-0500-00-0mes
Submission
7 May 2004
Tricci So
Slide 6
How 802.11 Defines Extended Service Set (ESS)?
• ANSI/IEEE Std 802.11, 1999 Edition, page 3 – 3.7: A set of one or more
interconnected basic service sets (BSSs) and integrated Local Area Networks
(LANs) that appears as a single BSS to the Logical Link Control (LLC) layer at
any station associated with one of those BSSs.
• ANSI/IEEE Std 802.11, 1999 Edition, page 12 – 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 (with the same ESS) transparently to LLC.
7. doc.: 11-04-0500-00-0mes
Submission
7 May 2004
Tricci So
Slide 7
What is Extended Service Set (ESS)?
What do you think this is?
Do you see
What I see ???
“Bridge” or
“Switch” or
“Router”
BSSs
Router
ESS
Wired Distribution
System (DS) =>
can be Layer-2
“or” Layer-3
NOTE: A DS can
be “wired” or
“wireless”
“Bridge” or
“Switch” or
“Router”
BSSs
ESS
According to 802.11
Specification, this is
Wireless Distribution
System (WDS), isn’t
it?
8. doc.: 11-04-0500-00-0mes
Submission
7 May 2004
Tricci So
Slide 8
What do 802.11s PARs say today?
• Scope of Proposed Project: To develop an IEEE 802.11 Extended Service Set (ESS) Mesh with
an IEEE 802.11 Wireless Distribution System (WDS) using the IEEE 802.11 MAC/PHY layers that
supports both broadcast/multicast and unicast delivery over self-configuring multi-hop
topologies.
• Purpose of Proposed Project: The IEEE 802.11-1999 (2003 edition) standard provides a four-
address frame format for exchanging data packets between APs for the purpose of creating a
Wireless Distribution System (WDS), but does not define how to configure or use a WDS. The
purpose of the project is to provide a protocol for auto-configuring paths between APs over self-
configuring multi-hop topologies in a WDS to support both broadcast/multicast and unicast
traffic in an ESS Mesh using the four-address frame or a derivative.
• Additional Explanatory Notes: The proposed amendment shall be an extension to the IEEE
802.11 MAC. The amendment will define a protocol for providing an IEEE 802.11 Extended
Service Set (ESS) Mesh using the IEEE 802.11 MAC to create an IEEE 802.11 Wireless
Distribution System (WDS) that supports both broadcast/multicast and unicast delivery at the
MAC layer using radio-aware metrics over self-configuring multi-hop topologies. An ESS Mesh
is functionally equivalent to a wired ESS, with respect to the STAs relationship with the
BSS and ESS. A target configuration is up to 255 devices (APs andn STAs), of which up to 32
of the devices may be APs participating in the ESS Mesh. However, larger configurations may
also be contemplated by the standard. The amendment shall utilize IEEE 802.11i security
mechanisms, or an extension thereof, for the purpose of securing an ESS Mesh in which all of
the APs are controlled by a single logical administrative entity. The amendment shall allow the
use of one or more IEEE 802.11 radios on each AP in the ESS Mesh.
9. doc.: 11-04-0500-00-0mes
Submission
7 May 2004
Tricci So
Slide 9
What Have We Been Say about ESS Mesh So Far?
Have we been talking WDS Mesh instead of ESS Mesh???
Router
Bridge
Distribution System
AP-STA Link AP-STA
Link
802.11 BSS
Mesh Wireless Links
802.11 ESS Mesh
802.11 ESS
10. doc.: 11-04-0500-00-0mes
Submission
7 May 2004
Tricci So
Slide 10
Have we been talking about WDS Mesh so far
rather than ESS Mesh?
Questions
How should we define WDS Mesh relative to
ESS Mesh?
What does ESS Mesh really MEAN anyway?
ESS { DSs, BSSs }
BSSs { APs, STAs }
ESS Mesh = ESSs in Mesh Configuration ???
