User's Manual Part 1

3: Detailed Description
APCD-LM043-8.0 (DRAFT C) 27
5. The EUM checks the destination MAC address. If the destination MAC address
appears in the Bridge Table, meaning the destination is on the Ethernet side, the
packet is discarded.
6. If the destination MAC address is the same as the EUM MAC address, then the
packet is forwarded to the EUM application; otherwise, it is forwarded through the
polling MAC and radio link to the CCU.
7. The CCU receives the packet through the CCU radio port. The CCU either updates or
adds the Ethernet address to the Address Table.
8. The CCU checks the port number. If the port number appears in the CCU Port Filter
Table, the packet is discarded.
9. The CCU checks the destination MAC address. If the destination MAC address is not
in the Address Table, the packet is sent to the CCU router application.
10. If the MAC address is the same as either the CCU radio or Ethernet MAC address, the
packet is forwarded to the CCU application; otherwise, the CCU gets the appropriate
gateway IP address from the Routing Table and the gateway MAC address from the
ARP Table, and then sends the packet to the gateway (most likely the NAP router)
through the Ethernet port.
NOTE: The CCU and EUM pass only IP, ARP, and PPPoE packets. All
other packets are discarded so non-Ethernet packets, such as
IPX/SPX, are not passed over the radio link.
3.3.4 Internet to End-user Computer Data Transmission using Switched
Ethernet Mode or Through Only Mode
In Switched Ethernet and Through Only modes, the CCU has only one IP address for both the
Ethernet and the radio interface.
1. Internet traffic comes through the gateway router, and possibly through backhaul and
Ethernet switches, to the CCU Ethernet port.
2. The CCU receives a packet through the CCU Ethernet port and checks the TCP or
UDP port number. If the port number appears in the CCU Port Filter Table, described
in Port Filter Table (CCU and EUM) on page 231, the packet is discarded.
3. If it is not already in the list, the CCU adds the source Ethernet address to the Bridge
Table, described in Bridge Table (EUM or CCU in Switched Ethernet or Through Only
Mode) on page 242.
4. The CCU checks the Bridge Table. If the destination address is in the Bridge table,
then the packet is discarded since it is not destined for a host in the CCU's radio
subnet.
5. Using the destination Ethernet MAC address, the CCU obtains the EUM ID from the
Address Translation Table, described in Address Translation Table (CCU only) on
page 238.
6. Using the EUM ID, the CCU obtains the EUM grade of service from the Registration
Table, described in Registration Table (CCU only) on page 240.