User's Manual

Doc. No.
Rev.
Date
DRAFT
1.01
2012-01-27
Damm Cellular Systems A/S, Denmark
TetraFlex
®
7.5 Manual - IP Backbone network layout and
configuration
TetraFlex® 7.5 Manual 2-153
2.16.3.3 Redundant BSC – SB421 or BS41x
In case the node has redundant BSC – the router will need to have optional module installed.
A 4-port switch module (HWIC-4ESW) is available from Cisco.
2.16.4 IP addressing schemes
IP addressing recommendation is based upon a 172.16.x.x address. Inside a given node –
the 4
th
octet of the address is assigned as the host address: .10 and .19 for BSC1 and 2. .11,
.12, .13 and .14 for the BS421’s. The 3
rd
octet is reflecting the node number.
For IP interconnection via routers, the subnet mask is set to 255.255.255.0 or /24.
For IP interconnection via switched network, the subnet mask is set to 255.255.0.0 or /16.
If changing these masks – remember to change also in the DHCP server on outdoor type
TetraFlex
®
.
All communication between the nodes in the multisite network is based purely upon IP. The
network must provide both unicast routing and multicast routing. Group calls and register
replication uses multicast communication and full duplex calls between two mobiles or to
external PSTN via SIP also uses multicast although in nature being point to point
In TetraOM connection to the BSC – use the command S71 to display the relevant settings in
regards to multicast networking.
224.239.016.000/28 is the default multicast address segment in use by the system for
register replication and for signaling of call activity between BSCs in the TetraFlex
®
network.
The address can be changed to meet special requirements. 224.238.016.000/28 results in a
address of 224.239.16.1 for exchange of control packets between BSCs and for call
signaling. Further an address of 224.239.16.3 is created – which is used for multicast traffic
relating to discreet listening. 224.239.16.4 is the multicast address used for replicating the
subscriber register
224.239.017.001 is the default multicast address in use for log server signaling. The address
can be changed to meet special requirements, amongst others allowing for more than one log
server.
225.000.000.000 is the so called CMoIP base address. CMoIP is the actual communication
data stream. The address can be changed to meet special requirements. It is possible to
change the two first octets of the address – whereas the two last octets are assigned
automatically by the system. This base address describes in the given example an address
range of 225.000.000.000 to 225.000.254.255.
The CMoIP address is assigned to calls in the TetraFlex system and signaled to all other
BSCs through the signaling group 224.239.16.1. The assignment of CMoIP address is done
by the originating BSC and is done as incremental and round robin – meaning start at
225.0.0.0, next call 225.0.0.1, and next 225.0.0.2 until 225.0.254.255. Then system restarts
numbering from 225.0.0.0.
When a BSC starts up – it automatically involves the IGMP (Internet Group Management
Protocol) and send off an “IGMP join” message to the network on the LAN. This “join” is sent