Subject: [Capwap] WLAN arch survey answer from Janusys Networks

From: "Tyan-Shu Jou" <[email-masked]>
Date: Tue, 11 May 2004 11:23:31 -0700

Hi all,

  It seems like the CAPWAP taxonomy document can use more survey results
on mesh topology, even though the deadline has passed. Upon the editor's
request, I am putting our answer of the arch survey (template v2) onto
the mailing list. Hope it can somewhat contribute to the CAPWAP work.
Thanks.

Tyan-Shu Jou
Janusys Networks, Inc.  
------------------------------ template starts here ----------------

contribution template for WLAN architecture survey 

(1) Design considerations & requirements: 

please briefly describe your design principles for this architecture.

Ans:
The architecture is to offer a WLAN mesh infrastructure-based ESS with a

self-configurable network and adaptive topology.
The access service can be easily set up and flexibly adjusted to reflect
the need. It can also be used to extend wireless service at places that
Ethernet wiring is difficult due to either cost or physical limitation. 

(2) WLAN functions supported:

Please list the functions supported in this WLAN briefly, but please do
not send us the entire 
data sheet. Examples of WLAN functions includes the STA services,
Distributed System Services (as defined by 802.11), radio resource
management and control, AP load balancing, mobility 
support, WLAN network wide security functions (including authentication,
encryption for privacy and integrity, etc.) and any others not listed
here but deemed important in your design.

Ans:
The STA access service to a WLAN mesh node is fully compliant with 
IEEE 802.11. Its transit services will be compliant with those specified
in the emerging IEEE 802.11 Task Group S.

(3) The functional architecture to implement the functions described
above: whether it is by autonomous AP
architecture, or "split" architecture. For split architecture, please
provide the functional mapping 
of WLAN functions onto the AP and AC -- with just enough details that
help us understand the kinds of functional
interface necessary between the two. For distributed architectures,
describe how the functionality is distributed
across the nodes in the network.

Ans:

A mesh node within an ESS mesh network can be an autonomous device that
acts as an AP to its local stations and as a traffic relay to
neighboring mesh nodes. In this distributed architecture, each mesh node
is 
expected to fully aware of the network topology of the ESS mesh network
through topology information exchanged with its neighboring nodes.

Alternatively, the split architecture can be applied to a WLAN mesh
network. The mesh nodes can leave certain functions (such as user
authentication) to a centralized AC in the wired network. Or, set of
passive nodes (APs) can satellite around an active/intelligent node
(AC). Network topology information is exchanged only among the active
nodes.

User access management can be decided either at the associated 
(autonomous or active) mesh node or at a centralized entity.

(4) The protocol used in between AP and AC, for split architecture; or
the protocol used between mesh nodes, 
for distributed architecture. 

Ans:
A proprietary protocol between AP and AC.
Another proprietary protocol between Mesh APs.

(5) The topological assumptions between the network entities (is it
directly connected, L2 switched, or L3 routed?) -- this also helps us to
understand the deployment scenarios.

Ans:
The ESS mesh is a L2 access network.
The management communication can be either L2 or L3 based.

(6) Security threat analysis: what kinds of threat introduced by the
architecture, and how that are addressed.

Ans:
Mesh nodes must authenticate each other and to secure the data
transmission among neighboring nodes. Other than this consideration, the
wireless mesh network has the similar security concern as other wireless
access network.

(7) Pros and Cons of this architecture, esp. in relation to the four
problems described in the CAPWAP
problem statement. Please keep the analysis at technical instead of
marketing level.

Ans:
Management requirement: Mesh APs are self-configurable.
                        They can form neighboring links and the
forwarding
                        Topology dynamically and automatically.
                        The optional centralized control can be used to 
                        monitor the network at real time.

Consistent configuration: Each Mesh AP node can learn the configuration 
                          from two sourcs: either from the network (via

                          neighboring nodes) or from the centralized
control.

Dynamic media: A mesh network is designed to reflect the dynamic 
               nature of a wireless access network. Its topology
               can be dynamically formed to reflect the radio situation.
               A centralized coordination is also possible in the
               described architecture.

Securing Access: See the answer for (6).

------------------------------ template ends here ----------------

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