User's Manual Part 1

4: IP Network Planning
APCD-LM043-8.0 (DRAFT C) 65
4.4 Through Only Mode
This mode should only be used for PPPoE networks where ALL subscriber traffic is to be
passed to or from a PPPoE server. This is a specialized configuration and not to be used for
most networks.
In Through Only mode, the CCU passes all radio network traffic to the CCU Ethernet network,
regardless of the Ethernet destination MAC address. This differs from Switched Ethernet
mode, where the packet would be passed back to the radio network if the Ethernet destination
MAC address is that of an Ethernet device on the radio network. Similarly, a CCU in Switched
Ethernet mode passes Ethernet broadcast packets received from an EUM out both the radio
and CCU Ethernet networks.
For Ethernet packets from the CCU Ethernet network, Through Only mode is the same as
Switched Ethernet mode.
4.5 Network Size Guidelines
In Routed mode, a single CCU can support up to 300
1
subscribers. Assuming one subscriber
per EUM, this limits a radio network to 300 EUMs, 300 subscribers, and 1 CCU, each an
Ethernet device, for a total of 601 Ethernet devices. This is an Ethernet broadcast domain.
This size of broadcast domain provides reasonable performance since broadcast traffic is
generally limited to ARP packets. The number of CCUs that can be served by a gateway
router port is limited by network capacity rather than by the size of the Ethernet network
broadcast domain.
In Switched Ethernet mode with a single CCU, the Ethernet broadcast domain is extended to
all devices on the CCU Ethernet network. If this number is limited to about 10 or so devices
(e.g., servers, UPS with Ethernet interface, etc.), then there should be little impact on the
network performance.
In Switched Ethernet mode with multiple CCUs, the Ethernet broadcast domain is spread over
all radio networks and the Ethernet network. Careful planning is required for good network
performance.
The guideline is to limit an Ethernet broadcast domain to no more than 650 Ethernet devices,
assuming most of the devices use the network lightly. In Switched Ethernet mode with multiple
CCUs in a single Ethernet Broadcast domain, this guideline of 650 Ethernet devices still
applies.
A general recommendation is that the broadcast and multicast traffic should not be more than
5 percent of the network traffic. Observation of the broadcast traffic may determine whether
the guideline limit of 650 devices applies to a specific network or not.
1. This assumes that all subscribers follow a reasonable usage profile. If one or more subscribers
use the network more than expected, then the radio network may experience degraded
performance with fewer subscribers.