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OBS core controller design and hardware realization

Print View , by: iSee ,Total views: 13 ,Word Count: 1855 ,Date: Fri, 26 Jun 2009 Time: 5:24 PM

O. Introduction

Optical Burst Switching (Optical Burst Switching, OBS) network is based on the existing technical conditions, combined with optical circuit-switched and the benefits of Optical Packet Switching, IP over WDM to achieve effective solutions. OBS network consists of core nodes and edge nodes. The main functions of the core node is based on packet burst control (BCP: Burst Contro1 Packet) to provide information channel routing and resource scheduling, set up optical switching matrix, for the unexpected packet BDP (Burst Data Packet) reserved for all-optical channel .

OBS network performance depends largely on emergency control packet core nodes in the processing speed, and OBS time offset (Offset Time) is directly related to the size. At present, the method of using software to achieve an agreement based on the JIT core node, processing speed of the general order of magnitude in ms. In order to improve the processing speed of BCP package, documentation of methods used hardware JIT agreement to control packet processing time of sudden dropped to middleweight us. JIT agreement, taking into account the simple scheduling algorithms, and scheduling to deal with fast module scheduling algorithm to achieve an independent and is not necessary, but will increase as a result of the additional module of the delay, and the need to consume more processing time. In this paper, a JIT-oriented protocol structure of the core-node controller, the network layer routing functions and OBS channel scheduling function layer into a module to deal with, on the one hand, the integration module can shorten the processing time of the BCP; On the other hand, the structure is transmitted after the implementation of scheduling, routing can be made optimal output channel is not available, the choice of other possible output ports and then the scheduling channel, thereby reducing lost the probability of packet.

1 Design and Implementation of Controller

Selected to achieve the establishment of an explicit estimate for removal of the JIT (Just-In-Time) signaling protocol SETUP message only, there is no news REALEASE. Core node SETUP message received and the completion of the treatment immediately after their set aside resources SETUP message in accordance with the bias included in the packet time and the release of resources to estimate the length of time.

1.1 system

Figure l for the OBS core controller system block diagram is divided into the receiving module, the frame analysis module, cross-matrix, sending module, routing and scheduling module. Between the various functional modules are provided with a cache structure, each module can be made independent, so the lines between the modules of work. The main functions of each module are as follows:

Receiver module to receive control channel data, after the restoration into Ethernet frames, write to the receiving cache.

OBS core controller design and hardware realization

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Frame analysis module to read from the cache to receive Ethernet frames, an agreement to resolve the corresponding domain information for the corresponding processing. BCP package if it is not directly transmitted to the operation; BCP package if it is to dispatch relevant information sent to the routing and scheduling module, and routing and scheduling module for forwarding the news of the return or discard.

Routing and scheduling module is responsible for network layer routing functions and OBS channel scheduling layer functions, including routing table contains a forward channel and a resource library, forwarding routing table to preserve the node routing table information for routing inquiries; record channel resources of the output ports of the nodes of the data channel resources occupied, and responsible for controlling the optical switch matrix.

Cross-matrix of the input buffer to the output of the packet switching cache. Send module update time BCP offset package, and then the composition of Ethernet frames sent to the Control Channel.

1.2 The main module of the Design and Implementation

1.2.1 Frame Analysis Module

Analysis of frame analysis module is responsible for the type of frame and content frame, and part of the network layer protocol and the OBS layer protocol processing, and routing and scheduling module control work. The main work can be divided into several parts as follows: l, to read from the cache to receive data packets received and recorded the time received for the updated package of bias BCP time; 2, network layer protocol processing , including the type of information, packet length, the purpose of obtaining the network address and the updated TTL and so on; 3, OBS layer protocol processing, including the calculation of bias and when asked to update the routing and scheduling of the control module; 4, on the good data processing package, upload it to the local packet network node module, the need to continue forward, then sent to the output cache.

OBS core controller design and hardware realization

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Frame analysis module state transition diagram shown in Figure 2. power to enter the Idle state after the first, in the Idle state to receive the cache to check whether there is any new data packets, so the state is entered ReadMAC, read mac header information to determine the type of MAC frame, non-IP packets will be its discarded, Otherwise, enter the ReadIP state, the state read the length of IP packets, as well as the type, TTL and other information, if it is not the BCP package, enter the Route, and for routing, if the local packet, then uploaded to the Network Management Module in, or enter the Update state; BCP package if it is, then enter the Route & Schedule status, routing and scheduling module to start the work. If the scheduling fails, the BCP should be discarded packets, if successful, also enter the Update state; in Update mode, the update of the TTL, if the scheduling by the change in its wavelength, but also to update the information. After entering the Forward, and good will has been updated to send the packet to the output cache for the next frame processing.

1.2.2 Routing and Scheduling Module

Figure 3 shows the routing table and channel structure of library resources. Routing table contains the number of routing table, each table entry, including the purpose of the network address and port number output of information in two parts. Find the process of routing as follows: from the beginning of the first table entry will be followed by the purpose of network address with the network address table entry match in, match the success of that output port number. Ptr to point to match the current table entry, for the second search, simply point to Ptr table from the beginning to find items.

OBS core controller design and hardware realization

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Channel resource library that contains all the port channel allocation information for each port as a group, including a control unit CU and a set of timers, each timer corresponds to a channel. Idle channel is idle timer is also time for the BCP after the success of the distribution channel, we need to open optical switch control signals, moving at the same time shoulder the corresponding timer, time set to offset + set aside time to time, from time to time the end of the closure of light switch control signal. Control unit can be based on the work of the state of the timer channel to determine the use of the state to carry out the distribution channel.

Figure 3 routing table and channel resources of the structure of routing and scheduling function of the realization of the process is as follows: first detection of the frame analysis module of the scheduling request signal, if so, read the purpose of the network address, at the same time start the process of routing and scheduling, first routing table to find the first match with the purpose of the network address of the routing table, the output port; Curitiba to channel resources to check whether the ports are idle data channel, any channel reserved for the set of optical switches matrix, the corresponding timer to start, scheduling success, returned to the frame analysis module output ports and data information channel; If there is no idle channel, you will need to continue to look for matching routing table entry to find the channel again to library resources Search free channel, so to continue; if you search for all the routing table after table entry can not be found after the channel is idle, then back to the failure of signals to the scheduling analysis module frame.

Test 2

We carried out the design and realization of hardware. Figure 4 for the use of tools QuartusII simulation of circuit timing diagram. 1,2,3,4,5 chart directions for the state of the signal, followed by the corresponding frame to complete receiving the signal, to read the state of the signal, the agreement to deal with the state of signal, signal routing and scheduling state, the state of the signal transmitted; 6,7 for the output signal , corresponding to the completion schedule set up signals and optical switching signal.

OBS core controller design and hardware realization

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Figure 2 BCP packet receive processing timing of the work (see the end) can be seen from Figure 4, in an OBS processing package, followed by experienced reading frame of data, protocol processing, routing and scheduling, forwarding and many other state , in which packets received from the BCP to issue a complete set of optical switches signal just lOOns, compared to the realization of the existing program has been greatly improved. Fully meet the existing network of OBS core node switching speed requirements.

3 summarizes

In this paper, a new channel routing and scheduling in a single module to address the OBS core node control system structure, and FPGA verification platform, the feasibility of the design and effectiveness. Test results show that: the receiving end to the issue of BCP packet optical switch setting signal for the shortest time lOOns. Significantly reduces the packet control node in the core processing time.

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