VDSL: beyond the distance limit of Traditional Ethernet

The birth of VDSL is not as elegant as ADSL, but more and more people are paying attention to it. Recently, TP-Link, known for pushing low-end network products, also launched a VDSL switch TD-VF1008. Tu qianliang, Project Manager of the TP-Link product department, stressed: "The biggest benefit of VDSL is that it breaks through the distance constraints of Traditional Ethernet ."

In fact, VDSL is similar to ADSL in terms of technical implementation. It achieves a higher transmission rate by reusing the upload and download pipelines. It also uses the built-in error correction function to compensate for noise and other interference. Maximum theoretical value of VDSL asymmetric transmission: 55 Mbps downstream, up to 19.2 Mbps upstream, or even higher. In addition, VDSL also supports setting symmetric Transmission to set symmetric 12.5 M ). The VDSL transmission distance can reach 1-kilometers. The transmission medium is a common telephone line and the transmission speed is fast. It is a good choice for broadband access. Like ADSL, VDSL is mainly used for real-time video transmission and high-speed data access. In terms of the compatibility of transmission information, VDSL can achieve the same telephone line as the original telephone line, ISDN, or even ADSL, and truly achieve the "three networks in one" ideal.

1.5 km copper Ethernet

The VDSL developed by TP-Link integrates Ethernet technology and VDSL technology, including the local device TD-VF1008VDSL switch and remote device TD9600VDSLModem, it can provide both voice services and VDSL services on the same telephone line. TD-VF1008VDSL switches provide 8-way VDSL access at the same time to provide remote users with VDSL and voice services. Each VDSL corresponds to a telephone line and is connected to the user's voice switch. A TD-9600VDSLModem can be directly connected to a computer's ethernet card.

The TD-VF1008VDSL switch system provides two-way symmetric 12.5Mbps transmission rate, the transmission distance can reach 1 km; if the two-way symmetric 4.167Mbps speed transmission, the transmission distance can reach 1.5 kilometers. On the one hand, TD-VF1008 is very suitable for fiber to the residential area after the "Last Mile" broadband access, especially residential areas, smart buildings, information-based hotels and campus broadband access; on the other hand, you can also use a telephone line to connect two locations over long-distance Ethernet and work-group-level access within the enterprise campus network.

As a VDSL Ethernet Switching Device, The TD-VF1008VDSL switching system adopts the QAM coding technology and has high bandwidth utilization. FDD can effectively prevent remote interference and lightning burst interference. TD-VF1008 uplink 10/100 Mbps Ethernet port supports 802.3x adaptive function and traffic control function, the entire system supports 8 VLANs, can achieve security isolation of different working groups, support port lock, prevent illegal users into the network.

Broadband Access

As a broadband access system, in addition to long-distance transmission, it must also support port isolation, user authentication, billing, and management. Tu qianliang pointed out that the following aspects should be taken into account when using VDSL for broadband access:

First, VDSL products must be able to isolate ports and divide VLANs. They must support the 802.1Q protocol or VLAN Based on ports. On the other hand, vswitches must support multiple security authentication methods, for example, it supports DHCP and Web Authentication. In addition, the most important thing is to support the IEEE802.1x Protocol. To support the passthrough transmission of 802.1xeap packets, some switches can also terminate the 802.1xeap packets.

The VDSL switch must support port aggregation. When the device provides multiple M uplink Ethernet interfaces, we recommend that you support port aggregation and IEEE 802.1ad. In addition, the VDSL switch should support the traffic control function. The VDSL switch also needs to support filtering broadcast, multicast, unicast, and illegal frames. It also supports other layer-2 packet filtering functions, such as source MAC addresses and device ports; in addition, multiple suppression policies, such as broadcast suppression and multicast suppression, need to be supported.

For video applications, VDSL switches must support the multicast function. In man networks with relatively complex topologies, the support for spanning trees is also very important. The VDSL switch may not support the billing function, but it must be able to transparently transmit some billing protocol packages to ensure the work of the billing system. In addition, it is also important to support user traffic statistics.

VDSL switches have higher requirements for network management. Apart from SNMP and other protocols, they can manage switches in the out-of-band, out-of-band, command line, and Web mode, and act as telecom network devices, VDSL also needs to be able to perform a port loop test to monitor and test physical lines.

At present, most VDSL devices are used in broadband access networks of telecom carriers and rarely used in enterprises. According to the analysis of this phenomenon, tu qianliang pointed out: "Currently, the main reason hindering users from accepting VDSL is the inconsistency of the VDSL standards ." The VDSL standard is still in the definition stage. Some associated standardization teams, such as ANSIT1E1.4 of the United States, ETSI of Europe, DAVICTheDigitalAudio-visualcouncer) the ATM Forum and the ADSL Forum are trying to regulate it. Once a standard is set for VDSL, users will be relieved of their worries about adopting this low-cost and high-efficiency solution.

1. VDSL: a qualitative change in Broadband Access Networks
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