High-speed access: 10 Gigabit all-optical Ethernet network (1)

1. Metro access

1. High-speed access requirements

Bandwidth acceleration is a significant feature of the rapid development of modern information society. From the operator's perspective, the demand for Household broadband acceleration, the emergence of IPTV operations, the construction of 2G/3G and LTE base stations and core networks, the expansion of business outlets and OSS systems, all of them propose IP, broadband, and comprehensive access requirements for the transmission network. From the perspective of government and enterprise customers, the number of leased line branches and bandwidth also increase exponentially, as shown in table 1 ). There must be an access platform that can meet the IP/ETH-based and High-Speed Integrated Access Requirements of the above businesses.

Table 1. bandwidth requirements of various projects

2. Traditional access methods

Traditional access methods include ADSL/VDSL, LAN, and SDH/MSTP. The new PON access methods are gradually becoming the mainstream under the support of carriers.

XDSL: copper cable access mode, which generally provides Ethernet interfaces. Generally, the downlink speed is no more than 20 M. In practice, the distance is controlled at around 2km, which is a typical "last mile" access.

PON: optical fiber access mode with a wide range of ONU interfaces. It can provide interfaces such as FE, GE, and POTS. The uplink bandwidth can be dynamically allocated and is related to the split ratio. The value is calculated equally at, and each branch is about MB. The downstream bandwidth depends on the system load, and a single user can reach 200 ~ About MB. The coverage scope is centered on the OLT, and the theory can reach more than 15km. In practice, the coverage scope is controlled within 10km, generally 2 ~ 5 km.

LAN: the LAN access rate is relatively high and can reach more than M. Generally, it is an Ethernet interface. The cable access covers several hundred meters to several kilometers, and the optical fiber access can reach more than 10 kilometers. In a sense, the LAN and PON are the same access type.

SDH/MSTP: 30 ~ within the urban area ~ 150 km) provides channels for base station backhaul and IP Access, interfaces are PDH, SDH, ATM, and ETH, and the branch speed ranges from 2 M to 10 M.

3. Access Mode Analysis

Among the above access methods, only PON can meet the access needs of high-speed bandwidth integrated services such as triple playback in terms of bandwidth, interface, and comprehensive access. However, PON access has some limitations.

First, it is difficult to ensure network reliability. Because PON is based on a bare fiber network, the reverse speed of the trunk protection cannot meet the telecom-level requirements, which requires the OLT to be too far away from the ONU. Otherwise, it is difficult to ensure line security and maintain the network, for example, road excavation, engineering construction, and frequent network cutover may affect the safety of optical cables and lead to network faults. In practice, it is generally controlled in 5 ~ Within 6 kilometers.

Second, it cannot cover the city. The theoretical coverage is 20 km, but the engineering practice is generally 15 km, and the OLT to ONU radius cannot be too large. Therefore, within a city, PON networks are destined to become edge access networks attached to Metro access or transmission networks.

Third, it cannot carry services such as 2G/3G/LTE base stations. In addition to the unreliable network, the hybrid transmission of telecommunication and broadband services also brings the risk of network attacks. In addition, LTE requires interconnection between NodeB, while the OLT has a strong L2 aggregation function, and the layer-3 forwarding function between branches is weak. It is not suitable for Base Station access.

In practice, PON is positioned as an edge Access Technology for IP Man. To meet the needs of a wide range of coverage and access to high-bandwidth value-added services, operators generally build multiple aggregation bureaus to sink the OLT location to the aggregation point or user edge, uplink access to the Metropolitan Area Network (man) Aggregation node through optical fiber direct connection or transmission network. Base station services use SDH/MSTP or other new IP-based transmission technologies, as shown in ip ran or PTN1 ).

Figure 1. Position of PON in man

Ii. CE access mode: 10 Gigabit all-optical Ethernet network

In view of CE's ability to replace SDH/MSTP and become a condition for mainstream next-generation transmission technologies, SDH/MSTP is considered to be part of the access layer in the 2G/3G base station backhaul network or ip man architecture. From this perspective, CE is a type of access network. CE access not only effectively avoids the defects of the preceding access modes, but also provides high-speed and reliable integrated service access within the city like SDH/MSTP. It is the best technology for high-speed urban access.

As a complete transmission system, CE can be divided into core, aggregation, and access layers. The typical CE Access Mode features can be summarized as one sentence: The H3C CE scheme is used as an example to describe the 10-Gigabit all-optical Ethernet ring network ).

1. 10 Gigabit network

The H3C CE implements a 10g symmetric channel from the access layer to the core layer. The access layer uses the CE3000 series. Each node can provide at least 24 GE optical ports for access and 10 gigabit uplink traffic. The convergence layer uses the CE5000 series to achieve 10 Gigabit port line rate forwarding.

IP Man 10 Gigabit access

Most traditional ip man networks use xDSL, SDH/MSTP, and PON for access. Due to the widespread bandwidth acceleration requirements of users, for example, China Telecom has made m access a standard for home broadband, it is difficult for xDSL and SDH/MSTP to meet the above requirements, although PON can achieve small-scale high-speed access, due to the limitations described above, there is a lack of conditions for the transfer of urban areas, and it needs to be attached to a high-speed urban access and transfer platform. CE's Metro coverage and 10 Gigabit access meet this requirement ..

Through ce access, the uplink optical fiber of devices such as OLT and SW is effectively reduced, the network security of the optical fiber is ensured, and the Link Utilization is improved, as shown in figure 2 ).