User Manual

2-11
C HAPTER
2
CONFIGURING NETWORK ARCHITECTURE
Chapter overview
This chapter describes a simple network topology. It provides an overview of how to
configure switches at the cell site, the head end, and the ISP sites.
Architecture overview
The hierarchy of the network architecture uses the concept of two layers: the access layer and
the backbone layer.
The functions of the access layer include connecting users — which include subscribers and
the ISPs — to the backbone layer.
Subscribers use components on the access layer (the CPEs and the base stations) to obtain
broadband network services. The subscriber’s CPE communicates with a base station over a
radio link which is commonly called the air link. The base stations that communicate with the
CPEs are grouped into cells. The base stations in each cell are connected to a switch at the
cell site and a base station LAN is formed. The switches at the cell sites then use WAN links
to connect to the head-end switch.
The ISPs also use the access layer to connect to the backbone layer. An ISP receives network
access requests from components on the backbone layer (specifically the AP server on the
management VLAN). These requests for access are sent to the appropriate ISP. The ISP then
grants or denies the request. If access is granted, the ISP provides the subscriber’s host
computer with an IP address and traffic is shaped for that host computer according to the
subscriber’s service level agreement (SLA). Traffic to and from the host computer travels
through the backbone layer
The functions of the backbone layer include quickly switching incoming WAN trunk traffic
to the management VLAN and to the ISP VLANs. The backbone layer also returns Internet
traffic from the ISP to the appropriate base station and subscriber’s CPE.