This module manages Cisco's WiMAX ASN Gateway (ASN-GW).
A WiMAX network supports wireless data communication through
WiMAX radio (802.16) technology.
The high level architecture of a first generation WiMAX network
with the respective protocols for each interface is shown below:
+--------------------------------------------------------+
| R2 |
+------+ +------+ +--------+ |
| | R1 | | R6 | | |
| MS |--------| BS |---------| ASN-GW | |
| | | | | |---+ |
+------+ +------+ +--------+ | |
| | | R3 |-----|
R8 | R4 | |----------| CSN |
| | | |-----|
+------+ +------+ +--------+ | |
| | R1 | | R6 | |---+ |
| MS |--------| BS |---------| ASN-GW | |
| | | | | | |
+------+ +------+ +--------+ R2 |
| |
+--------------------------------------------------------+
The diagram below depicts the relation of the subscriber to the
session and flows:
+--------+ -Flow (connected via data path)
| ASN-GW | - Subscriber -Session -Flow (connected via data path)
+--------+ | -Flow (connected via data path)
| -Flow (connected via data path)
|
+--- (connected via signaling path)
A subscriber initiates a call from a MS. A session is created
between the BS and the ASN-GW for that call. Multiple flows can
be created for the session with different QOS parameters. For
example one flow can created for a voice stream and another
for data. Data paths are created between the BS and ASN-GW to
forward the data packets of the created flows.
When the first subscriber from any MS connected to a BS
initiates a call via the BS to the ASN-GW, a signaling path is
created between the BS and the ASN-GW. There is only one
signaling path between each BS and ASN-GW. Signaling paths
and base stations can be used interchangeably.
The signaling and data paths remains active as long as there are
subscribers connected to the ASN-GW from any MS connected to the
BS. If a path has no session/flow connected, it will be purged
after a certain period of time. This situation can occur when
all subscribers on a certain path are disconnected. A subscriber
disconnecting from a certain path does not indicate that the
subscriber has left the network, it could simply be handing off
to a different path.
The IP addresses of the signaling and data paths can be the same
or different both in the BS side and in the ASN-GW side.
+--------+ +--------+
| Base | | ASN-GW |
| Station| | |
| | SigPath | |
| IP(B1)|<............>|IP(A1) |
| | | |
| | | |
| | DataPath 1 | |
| IP(B2)|<............>|IP(A2) |
| | | |
| | DataPath 2 | |
| IP(B3)|<............>|IP(A3) |
+--------+ +--------+
Relationships:
Base Station 1 to many Mobile Stations
ASN-GW 1 to many Base Stations
Subscriber 1 to 1 Sessions
Session 1 to many Flows
Datapath 1 to many Flows
Signaling Path 1 to 1 Base Station
Acronyms and terms:
AAA AAA refers to a framework that specifies the
protocols procedures for authentications,
authorizatitin and accounting associated
with the user, MS and subscribed serviced.
AGW ASN-GW
ASN ASN (Access Service network) is defined as
a complete set of network functions needed
to provide radio access to a WiMAX
subscriber.
ASN-GW ASN-Gateway is a logical entity that
represents an aggregation of Control Plane
functional entities that are either paired
with a corresponding function in the ASN
(for e.g BS instance) a resident function is
the CSN or another functions in the ASN.
For every MS, a BS is associated with
exactly one default ASN-GW. However,
ASN-GW functions for every MS may be
distributes amongst multiple
ASN-GWs located in one or more ASNs. The
ASN-GW utilizes Session Redudancy to ensure
a backup ASN-GW is available in case the
primary ASN-GW goes down.
BS Base Station is a logical entity that
represents an aggregation of Control Plane
functional entities that are either paired
with a corresponding function in the ASN
(e.g. BS instance), a resident function
in the CSN or a function in another ASN. The
ASN-GW may also perform Bearer Plane routing
or bridging function.
BSID The Base Station Identifier is a global
unique identifier for a WiMAX base station.
CPE Customer Premise Equipment.
CSN CSN (Connectivity Service Network) is
defined as a set of network functions that
provide IP connectivity services to the
WiMAX subscribers.
Data Path Corresponding to each subscriber, data paths
are created to foward packets between the
ASN-GW and the subscribers.
DPID Data Path ID is used to identify the tunnel
carrying MS traffic between ASN gateways or
between the ASN gateway and base station.
As of 8/28/07, only the GRE key is to be
used as the DPID.
Flow A service flow is a unidirectional logical
flow between the network and the Subscriber
Station. A service flow is created to handle
a different QoS over the connection oriented
MAC. A subscriber can have multiple service
flows associated and each service flow is
associcated with an uplink and downlink
classifier.
GRE Generic Routing Encapsulation. Refer to
RFC 1701 for more details.
LB Load Balancing
Messages Messages are packets exchanged on the
signaling paths.
MS The Mobile Station is a generalized mobile
equipment set providing connectivity between
subscriber equipment and a base station (BS)
The Mobile Station may be a host or a CPE
type of device that can support multiple
hosts.
MSID The Mobile Station Identifier is the 802.16
identifier used for all subscriber stations,
and is used in all the messages over R6. The
identifier associates all requests from a
mobile to the ASN-GW.
Packets Packets are datagrams fowarded over the data
paths.
R1 Communication protocol between mobile and BS
as per the air interface (PHY and MAC)
specifications (IEEE P802.16d/e). R1 may
include additional protocols related to the
management plane.
R2 The interface between the MS and CSN
associated with Authentication,
Services Authorization, IP Host
Configuration management, and mobility
management. This is a logical interface thus
does not reflect a direct protocol interface
between MS and CSN.
R3 The interface between the ASN and the CSN to
support AAA, policy enforcement and mobility
management capabilities. It also encompasses
the bearer plane methods (e.g., tunneling)
to transfer IP data between the ASN and the
CSN.
R4 Communication protocol between ASN-GWs.
R4 consists of a set of control and bearer
plane protocols originating/terminating in
various entities within the ASN that
coordinate MS mobility between ASNs.
In Release 1, R4 is the only interoperable
interface between
heterogeneous or dissimilar ASNs.
R5 Consists of a set of control plane and
bearer plane protocols for internetworking
between CSNs operated by either the home or
visited NSP.
R6 Communication protocol between ASN-GW and BS
R6 consists of a set of control and bearer
plane protocols for communication between
the BS and the ASN GW.
The bearer plane consists of intra-ASN
data path or inter-ASN tunnels between the
BS and ASN-GW.
The control plane includes protocols for
IP tunnel management (establish, modify, and
release) in accordance with the MS mobility
events. R6 may also serve as a conduit for
exchange of MAC states information between
neighboring BSs.
R8 Communication protocol between base
stations.
R8 consists of a set of control plane
message flows and, in some situations,
bearer plane data flows between the
base stations to ensure fast and seamless
handover.
Bearer plane consists of protocols that
allow the data transfer between Base
Stations involved in handover of a
certain MS.
Control plane consists of the inter-BS
communication protocol defined in IEEE
802.16 and additional set of protocols
that allow controlling the data
transfer between the Base Stations involved
in handover of a certain MS.
Session Session is a connection between one or more
MS and a network element in order to
exchange link-level frames or packets.
SFID The service flow is identified using a SFID
(Service Flow Identifier).
Signaling Path A signaling path exists between the BS and
ASN-GW, and is used for all signaling such
as creating, dleteing, authenticating,
as we as additional functions related to
the subscriber.
SR Session Redundancy
Subscriber The 802.16 subscriber entity connects over
the 802.16 airlink, and eventually results
in the creation of the subscriber object at
the ASN-GW.
UHO Unpredicitive Handoff
PMIP Proxy Mobile Internet Protocol
HA Home Agent
REFERENCE
[1] WIMAX Forum Network Architecture,
(Stage 3: Detailed Protocols and Procedures)
Release 1.1.1 September 14, 2007.
ciscoAgwMIB
ciscoAgwServiceDownNotif 
cagwInstanceTable 
cagwInstanceEntry 
cagwInstanceIndex 
cagwNotifEnabled