What Is IP DSLAM?

ip dslam (Internet Protocol, Digital Subscriber Line Access Multiplexer, full English name internet protocol digital subscriber line access multiplexer) ip dslam is used as an access device, and user traffic is mainly based on IP. The traditional 20th century dslam uses asynchronous transfer mode (atm) technology to connect to the ATM upstream router. Then extract the IP traffic of these devices and pass it to an IP network. The ip dslam device extracts its own IP communication in the dslam device. So it is all ip from there.

IP DSLAM

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ip dslam (Internet Protocol, Digital Subscriber Line Access Multiplexer, full English name internet protocol digital subscriber line access multiplexer) ip dslam is used as an access device, and user traffic is mainly based on IP. The traditional 20th century dslam uses asynchronous transfer mode (atm) technology to connect to the ATM upstream router. Then extract the IP traffic of these devices and pass it to an IP network. The ip dslam device extracts its own IP communication in the dslam device. So it is all ip from there.

The traditional dslam is a completely ATM-based device, which is often referred to as the dslam based on the ATM method. It provides atm interface (such as 155mbit / s atm interface or n * 2mbit / s ima atm interface), Shanghai Metropolitan Area Core Network, with atm vp / vc cross-connection, provides atm traffic aggregation, and is implemented by atm's qos technology Service quality of service and flow control. The vast majority of dslams currently installed on the Internet are dslams in this way. However, in many areas, operators have no longer expanded their existing metro ATM core networks and switched to building IP broadband metro core networks. Therefore, with the decreasing availability of metro ATM resources, ATM-based dslam has become increasingly difficult to adapt to the needs of actual networking, and ip dslam will become the direction of dslam's future development.

1. Implementation principle ip-dslam is the same as atm dslam in the processing of adsl signals. The uplink signals are demodulated by dslam and converted into adsl signals. But in ip-dslam, these atm signals do not perform multiplexing and service type processing as in atm dslam. Instead, they implement the aal5 sar function and convert them into corresponding mac frames, that is, atm termination. During the termination of atm signals, , Establish the corresponding relationship between the corresponding mac address and pvc. After the ATM signal is terminated, it is transmitted to the upper layer device through the fe uplink port of the LAN board, and enters the IP metropolitan area network. The downlink signal is just the opposite. The MAC frame signal sent from the upper-level device to the ip-dslam completes the signal processing of the second layer function. Finally, the aal5 sar function is used in the ip-dslam to convert the mac frame into an atm cell and realize Mac address to PVC conversion. The atm signal in the ip-dslam is processed, converted into an adsl signal format, and transmitted to a remote adsl modem through modulation. Adsl users can access through bridged private line or pppoe, establish 1483 (bridged) bridged PVC on atu-r, establish internal PVC connection between adsl port and LAN cell vlan through dslam, and the LAN board terminates PVC and 1483 (bridged) bridge protocol, which is converted into an Ethernet packet to access the lan switch module in the lan board and upstream. When an adsl user accesses in pppoe mode, pppoe dial-up software needs to be installed on the user's pc, and ppp calls are terminated on the bas device. 2. The application network ip dslam uses the fe port of the lan board to provide the uplink ip interface, and connects to the backbone node of the metropolitan area network through the uplink device. The system supports the trunk uplink function of 4 fe ports, and the data stream directly enters the IP data network at high speed, avoiding serious bandwidth bottlenecks caused by traversing the two networks of ATM and IP; the system has good user security management, and achieves the Layer isolation and three layers of controlled mutual visits prevent illegal users, address theft, spoofing, and malicious attacks.

The ip dslam is divided into two forms from the perspective of the implemented functions. One form of dslam only processes the ethernet layer (layer2), and the other form of dslam not only processes the ethernet layer, but also the ip layer Processing and integration of broadband access server bas functions. The first form of dslam performs the following functions. 1. 1. Support local forwarding enable / disable control of Layer 2 ethernet data packets; 2. Support port-based Layer 2 ethernet packet filtering. Some devices also support packet filtering based on mac address (including source mac address and destination mac address). Support Layer 2 isolation of different adsl ports; 4. 4. Support ieee 802.1q protocol, support VLAN division by port, and some devices also support VLAN division by mac address; 5. Broadcast storm suppression, which can suppress the traffic of broadcast packets and multicast packets; 6. Port configuration, port status query and setting, port-based data flow sending and receiving statistics; 7. 7. When dslam provides multiple fe / ge uplink ports, it supports ieee802.3ad link aggregation function; 8. 9. Support flow control function; Support igmp snooping multicast function. In addition, some devices also implement ieee802.1p priority control, ieee802.1d spanning tree function, and 802.1x port access control function. The dslam of the second form has the following functions in addition to the functions of the ethernet layer. 1. 1. IP data packet forwarding, support static routing, ripv2, ospf protocol; 2. Support IP multicast, and support IP multicast igmpv2, dvmrp, pim protocol; 3. Support user access rate control; 4. Support IP priority control and queuing strategy (wrr, drr, wfq, wf2q, etc.), some devices also support congestion control function; 5. Support dynamic and static user IP address assignment; Broadband access server function. Currently, mainstream broadband access servers support pppoe / pppoa user access control, and some devices support both pppoe / pppoa and 802.1x authentication. Since the bas function is integrated, the following functions are also available. 7. 8. Support the anti-theft of IP address of adsl private line users; 9. Support the binding of access accounts and ports for adsl users; 10. Support to limit the number of IP addresses obtained by adsl under the same PVC; 11. Support local and radius user authentication methods; It must support automatic detection of users' abnormal offline, release corresponding network resources, and stop billing. 12. Provides accounting information of users based on duration and traffic after successful authentication.

1. 1. Fully distributed ATM and IP conversion, greatly improving the overall processing capacity of the equipment, dispersing the risk of equipment failure, and improving the performance and stability of the equipment; 2. Fully distributed ATM conversion, which can directly correspond to ATM PVC and VLAN ID, meet the security requirements of private line users, and support VPN-based VPN applications; 3. Fully distributed ATM conversion, which can make full use of mature and cheap three-layer switching architecture, provide very high backplane switching capability, support adsl wire-speed forwarding, and eliminate equipment switching bottlenecks; 4. IP core design, can use high-capacity switching backplane to provide high-bandwidth port support capabilities, can support multiple ge / fe interfaces, and eliminate equipment upstream bandwidth bottlenecks; Due to the use of the IP core design, there is no need to be restricted by the expansion of the ATM bus. The use of high-density and high-bandwidth ports can achieve flexible cascade expansion and support single-point user capacity that is more than 7 times larger than traditional methods; 6. When users migrate, there is no need to make full configuration of atm pvc, and the client and network can continue to provide services to users without making any changes, which greatly shortens the time of business changes and reduces the workload provided by the business; 7. 8. Using the multicast support capability provided by the ip core, multicast services and video-on-demand services can be opened on dslam and uplink devices, which improves the network's service provision capabilities and lays a superior network foundation for more value-added applications; Supports fully distributed pppoe authentication, which can provide users with authentication, billing and management capabilities without centralized bras equipment and is fully compatible with the original operating model, avoiding the performance, stability and business support capability bottlenecks introduced by centralized bras, improving 8. Stability of the entire network and the ability to provide bandwidth; Adopting fully distributed authentication, inheriting the ability of pppoe authentication to manage users, and since user authentication can carry the physical location information of each user (the IP address of the dslam and the physical port number of the user on the dslam) to radius, 10. It is very easy to check the IP address. 11. Adopt fully distributed pppoe authentication, which can use the binding ability of account + port to provide the network security required by the operator and prevent the loss of tariffs; Using pppoe authentication, data can be generated on radius according to user requirements when opening an account, and bandwidth is dynamically allocated without the need for configuration per device or complicated PVC configuration, saving operating costs, and providing monthly bandwidth, duration + bandwidth + preferential policies, etc. Complex billing policies, enriching the adsl product line;