User's Manual Part 1

4: IP Network Planning
APCD-LM043-8.0 (DRAFT C) 71
4.7.3 How many subscribers are supported per EUM?
Number of Subscribers per EUM
Network analysis shows that the maximum number of subscribers per radio network is 300,
assuming a given subscriber profile. If there are subscribers that use more resources than this
profile, then the network performance will start to degrade with fewer subscribers.
With only one subscriber per EUM, this translates to a maximum of 300 EUMs. However, more
than one subscriber can use an EUM.
Up to 50 subscribers can have network access through one EUM if the EUM’s maximum
number of customers is increased. The added subscribers are part of the Ethernet broadcast
domain. Regardless of the CCU protocol mode, the added subscribers see all Ethernet
broadcasts. This situation is fairly easy to recognize and manage.
An alternative approach is for the subscriber to set up a home network with a router connected
to the EUM. NAT allows any number of unseen subscribers to use the radio network. This will
use more network resources than would be expected for a single subscriber but is not easily
distinguished from a single subscriber who is a heavy user.
The advantage of using a router is that all Ethernet broadcasts from the added (unseen)
subscribers are not passed over the radio network. Only one MAC address is required and
only one IP address is assigned.
If the subscriber wishes to use his own public IP addresses with his router, it is possible to add
special routes to the CCU in Routed mode or to the gateway router in Switched Ethernet mode
to route traffic over the radio network to the subscriber’s router.
It is your decision whether to allow more than one customer per EUM and whether to permit
subscribers to use routers attached to the EUM. It is, however, difficult to detect the latter.
4.7.4 What subnet masks are recommended in the different protocol
modes?
Routed Mode
Since all EUMS, as well as subscribers, must be on the same subnet, the largest possible
radio network would require 601 IP addresses: 300 for the EUMs, 300 for the subscribers, and
one for the CCU. This requires a 22-bit netmask, allowing 1022 host addresses, plus the
subnet number and subnet broadcast addresses. If private IP addresses are used, there is no
reason not to use this size of subnet.
Most networks never become that large. More often, larger networks are divided between two
or more CCUs to provide higher service levels to subscribers. If the maximum network size
can be limited to 510 hosts (e.g., 1 CCU, 254 EUMs, and 255 subscribers), then a 23-bit
netmask can be used.