Study On Realizing Vlan's Function In HFC Network

Great market potential brings many kinds of access network technologies; each of them has their own portion of market. Among them, the broadband access based on HFC network is one of the best.technology; it has the advantages of high speed, low cost, multiple services, and excellent enhancement ability.VLAN, a new kind of technology based on switch network, plays a more and more important role in network design and management. VLAN is composed of many members. Although these members are located on different physical LANs, they can communicate with each other like that in one LAN, with no limitation of their locations, which makes it highly valuable on many applications. Firstly, it greatly enhances the centralized management of dynamic network while decreases its costs. Secondly, it can set up virtual work group easily. Thirdly, it decreases the network's demands of Routers. Finally, it improves the security of network.As VLAN technology has these advantages, we hope to introduce its functions in HFC network to solve the security problems that exist in our CMTS and CM products when they are used in HFC network.HFC network is a specific kind of shared-medium LAN and it has essential differences with switch network in topological architecture. We introduce functions of VLAN in HFC network, not to completely implement VLAN that based on switch network, but to control the communication of CM groups in a software way. So, it can be realized only by some necessary change of CMTS control code. It needs no extra hardware or complete redevelopment of CMTS control code.The same as that of network adapter, MAC address of CM is a unique 48 bit binary physical address, which can be use as CM's identity. Because CMs are registered when they are installed in HFC network, CMTS acquires the MAC addresses of all of the CMs in the system. Therefore, we can divide the CMs into many groups according their MAC addresses. That is, the CMs allowed to communicate with each other are gathered in the same group and assigned the same Group ID; those not allowed to communicate with each other are divided in different groups and assigned different Group IDs. Then, we can control the communication of CMs by compare their Group IDs. We have tested this method in the HFC network of our lab. The result shows thatthis software method can successfully control the communication of CM groups, offering the HFC network VLAN functions.