Ranging is one of the key technologies in Broadband Passive Optical Network based on the ATM (BPON) system. It is complex for software designers and difficult to test. In order to simplify the ranging procedure, enhance its efficiency, and find an appropriate method to verify it, a new ranging procedure that completely satisfies the requirements specified in ITU-T G.983.1 and one verifying method is proposed in this paper. A kind of ranging procedure without serial number (SN) searching function, called one-by-one ranging are developed under the condition of cold PON, cold Optical Network Termination (ONU). The ranging procedure includes the use of OLT and ONU flow charts respectively. By using the network emulation software OPNET, the BPON system is modeled and the ranging procedure is simulated. The emulation experimental results show that the presented ranging procedure can effectively eliminate the collision of burst mode signals between ONUs, which can be ranged one-by-one under the controlling of OLT, while also enhancing the ranging efficiency. As all of the message formats used in this research conform with the ITU-T G.983.1, the ranging procedure can meet the protocol specifications with good interoperability, and is very compatible with products of other manufacturer. According to the present study of ranging procedures, guidelines and principles are provided, Also some design difficulties are eliminated in the software design.
As EPON system becomes attractive integrated broadband access solution in worldwide Fiber To The Home(FTTH) and Fiber To The Building (FTTB) deployment, the QoS guarantee and the management of multiple services is inevitably a urgent issue in EPON system implementation. Instead of only using priority method as defined in IEEE802.1p, this paper proposes a native model for multi-service access platform with SLA enforcement, which specifying Service Level Agreements (SLAs) on logical links in EPON transmission segment and strictly enforcing SLAs by EPON MPCP protocol and DBA algorithm in both upstream and downstream. SLA normally uses multiple parameters to describe requirements of service bandwidth, delay and jitter. In EPON, the specification of SLA for service may use 4 parameters: the minimal Guarantee bandwidth, maximum allow bandwidth, sensitivity of delay and maximum burst size. As EPON schedules traffic on logical link basis, the right QoS demand of each service will be the same as its logical link. To guarantee different services' different SLAs, it was supposed to use multiple logical link IDentifies (LLIDs) in each remote ONU, each service is mapped to its own LLID. By classifying services packet into different links, combining with powerful Hierarchical WRR schedule algorithm it is possible to guarantee the bandwidth and control transmission delay and jitter for each service bidirectional. The proposed scheme has overcome the best-effect forwarding deficiency of the Ethernet, brought the management of multiple services and the management of remote ONUs into a new framework, given cost efficient and effective solution for EPON multiple services access.
Proc. SPIE. 5626, Network Architectures, Management, and Applications II
KEYWORDS: Lithium, Light emitting diodes, Fiber to the x, Remote sensing, Networks, Passive optical networks, Telecommunications, Local area networks, Broadband telecommunications, Standards development
Ethernet Passive Optical Network (EPON), which represents the convergence of low-cost Ethernet equipment and reliable fiber infrastructure, appears to be the best candidate for the next-generation broadband access network. A coin has two sides. Although EPON inherits the benefits of Ethernet, it also suffers some disadvantages. With its origin as a LAN technology, where “best effort” delivery and 99.96% uptime were acceptable, Ethernet was never considered to be a candidate for achieving “carrier-class” status, mainly because lack of powerful OAM capabilities. That’s to say OAM function is essential to carrier-class EPON. In this study, the principals of EPON and OAM, together with the necessity of OAM, are presented firstly. Besides, different ways to provide OAM in ITU-T APON, GPON are analyzed respectively. Three means to obtain EPON OAM, using MAC Control Frame, Physical Link Service Overhead Coding Sublayer (PLSOCS) and Reconciliation Sublayer (RS) Preamble are proposed in detail. Moreover, the main functions, such as remote failure indication, remote loop-back, link monitoring and variable retrieval are studied subsequently. After that, the concrete implementation of OAM in EPON is addressed, combining with hardware and software. As a result, an effective way to carry out EPON OAM can be easily drawn.
Ethernet Passive Optical Network (EPON) has been considered as the best candidate of the next generation access network, because of it’s particular advantages, such as inexpensive, simple, scalable, and capable of delivering bundled voice, data and video services. However, the standard isn’t approved, many questions are still discussing. Dynamic Bandwidth Allocation (DBA) is one of the hop topics. If we use static bandwidth allocation in EPON system, slots may not be filled to capacity in the case when the OLT grants to an ONU a slot smaller than the ONU requested based on its queue size. Then the packet will have to wait for the next slot, so there is an unused remainder at the end of the slot. As a result variable-length packets don’t fill the static slot completely. Conventional E-PON uses a slot-size based DBA algorithm. Packets of all priorities are put in the same slot. Due to the burstness of traffic and packet length variation, the starting point of each slot is push-pulled from frame to frame, as a result delay variation of packet is not under control. We can not support appropriate Qos to real-time traffic. In our design, we divide Ethernet data into three parts, one is the steady part that has N time slots for voice traffic, corresponding to N ONUs. In this case, there are M ONUs those has video traffic for transmit, the second part having M time slots will be established named Quasi-dynamic. And the other is the dynamic part that is basically one giant slot for data traffic, shared by all ONUs. Since the steady part of the frame can be approximated by constant flows, it will make influence upon voice. Establish or remove Quasi-dynamic channels will take less than 50ms delay variation. So this arithmetic can match the video’s character of less than 100-ms maximum jitter. Usually, for the low priority class traffic, there is no requirement on any QoS parameters; therefore, optimizing throughput is the goal. So we use IPACT algorithm in the third part, making utilization almost 100%.
Recent years, data traffic is increasing at an unprecedented rate. Digital Subscriber Line (DSL) and cable modem (CM) networks will not afford the huge bandwidth consuming in the near future. Ethernet Passive Optical Network (EPON) is an inexpensive, simple, scalable, and capable of delivering bundled voice, data and video services to an end-user over a single network. EPON, which is a typical point to multi point topology, has become an attractive technology to both vendors and carriers. To ensure compatibility with the IEEE 802 architecture, Logical Link Identifier (LLID) tag is introduced in EPON to achieve point to point emulation. Usually one LLID tag associates with one stream or one ONU (Optical Network Unit) which is remote device of EPON. In order to simplify operations, LLID tag is added as part of preamble in Optical Line Terminal (OLT) Reconciliation Sublayer (RS) and is checked at ONU side. It’s urgent to have a powerful mechanism to achieve dynamic LLID filtering. Just in the downstream, each packet must have its own LLID according to the Destination Address field before being sent; in the upstream, LLID is learned based on the Source Address Field of the packet. Although address filtering is very popular in the L2 switch chips, it can’t be applied to EPON LLID filtering directly, owing to EPON is neither a point to point network nor a broadcast network. In this paper, the main principles and features of Logical Link Identifier (LLID) tagging system are firstly explained, and then the process of LLID both in OLT and in ONU side is described. What’s more, a novel method to realize dynamic LLID filtering is discussed in detail, involving in LLID scanning, LLID learning, LLID aging, and so on. An erasable Content Addressable Memory (CAM) structure is used to meet this demand. Not only the architecture of the concrete circuits, but the related timing sequences, operation process, service arbitration and aging state transition diagram are presented. Note that this mechanism has been verified in the actual EPON system and worked very well. At last, some conclusion remarks about using LLID filtering to enhance the performance of EPON is given.
Ethernet Passive Optical Network (EPON) aims at providing full services to end users over a single platform, which combines the low cost Ethernet equipment and economic fiber infrastructure, appears to be the best candidate for the future broad access network. Due to Ethernet has a seamless connection with modern IP network, EPON has shown excellent performance when transmitting data service. However, a key technical challenge for EPON vendors lies in enhancing Ethernet’s capabilities to support real-time services, such as VoIP, live video and other TDM services, e .g. POTS and T1/E1. In order to guarantee the required QoS, many new technologies are introduced, either common to all IP based network or dedicated to EPON network. Firstly, a short overview of EPON technology is given. Then, two prevailing QoS architectures, Intserv and Diffserv, are presented in detail. Both their advantages and disadvantages are also discussed. Subsequently, the light is turned to a certain DBA algorithm, which is more efficient in EPON. Both the features of the algorithm and the main ideas are described in particular. At last, reserving bandwidth for TDM service, which is simple but not very efficient, is also proposed.
A dynamic bandwidth allocation policy to better support the TDM services in EPON is proposed. The analytical and simulation results prove that the proposed scheme does best in what it is designed to do.
A newly broadband access technology comes into being with the combination of IP and access technique, which is considered as EPON (Ethernet passive optical network). EPON system resolves the limitation of point-to-point, instead uses the topology architecture of point-to-multipoint. It extends the fiber cable to the last mile, so we can get the end-to-end network system with high efficiency, well expansibility and low maintenance cost. There are many key techniques and problems in EPON system, for example, CDR (Clock and data recovery), RTT (Round-Trip Time), DBA (Dynamic Bandwidth Allocation) and ULSLE (Upper-Layer Shared LAN Emulation). The essential character of MPCP (Multi-Point Control Protocol) used in EPON is to schedule the transmission of the upstream data packets, and to avoid data collision. A central counter is applied to synchronize the upstream data through a time-stamp flag. A REPORT control frame is transmitted, which give the length of the different priority queues. On receiving this control frame, central office device modifies the bandwidth allocation in the grant table. The function relating to the ULSLE protocol is similar with IEEE802.1D Bridge, and also includes point-to-multipoint, therefore so many problems are resolved, such as the frame reflection, the communication among different ONUs.