New Added Modules in the NCTUns

4.2.1.Optical Physical Module (named “ophy”)

I. The ophy module simulates optical fibers. It simulates the propagation delay, the bit error rate, and the bandwidth. It also provides the function that you can set the optical fiber failed during a certain period of time.

II. The ophy module provides packet trace log. It also provides

accumulation data log such as drop rates, collision rate, and throughput.

III. This module is used for any type of our all-optical networks.

4.2.2.Optical Port Module (named “op”)

I. The op module reads the optical header of a packet and it sends the packet to the destined wavelength channel. From the view point of the NCTUns, the op module decides which ophy module the packets should go to.

II. When it receives a LPC (light path configuration) packet, it records the coming-in wavelength number and the going-out wavelength number, and it adds the information on the LPC packets.

III. This module is used for any type of our all-optical networks.

4.2.3.Management Module (named “opmanage”)

I. This module is the main body of optical network protection and survivability.

II. The main functions of this module are constructing the protection ring

and maintaining the survivability of the optical networks. The module will re-switch the traffic to the protection paths if the working paths are broken.

III. The opmanage module has a table of protection rings. This table contains the mapping information of working path and protection path. In general cases, working path is the default way to transmit traffic. The protection path is the backup path when the working path is failed [2, 3].

IV. When the working path is normal, the opmanage module acts as a port-layer multiplexing module. The work of this module is deciding which port the packets should go to.

V. When the opmanage module detects a working-fiber failure, the module will switch the traffic to the protection fiber.

VI. The module is used for our all-optical network systems, but the

protection feature is available only in traditional all-optical network. In optical burst switching networks, it is only a module deciding which port the packets should go to.

4.2.4. Wavelength Assignment Modules (the one is named “wa” at switches, and the other is named

“rwa” at routers)

I. The two modules handle the routing and wavelength assignment

configurations. The rwa module is in the router, and the wa module is in the switch. They are used only in the traditional all-optical networks.

II. The rwa module generates the optical header. The modules below the

wavelength channel according to the information of optical header.

III. The wa module stores the light path configurations, and it helps the osw module to build its switching table. For example, if there is a light path

“1-2-3-6-7, wave 1”, the wa module in node6 will remember “I will send the packets to port 7, wavelength 1, if the packets come from port 3, wavelength 1.”, and it updates the switching table in the osw module.

IV. We will discuss the cooperation of the 2 modules with dynamic RWA scheme and static RWA scheme at Chapter 5.

4.2.5. Optical Switching Module (named “osw”)

I. It is the switching management module. The function of this module is switching the incoming packets to the right light path according to the switching table.

II. The osw module creates and maintains a switching table. The format of this table is: [in-port][in-wave]-[out-port][out-wave].

III. The wa module will tell the osw module the switching information. This is the only way that the osw module obtains the switching information.

The wa module creates switching information, and the osw module stores the information and executes the traffic switching.

IV. It is used by all of our all-optical network system.

4.2.6. Optical Burst Switching Module (named

“obsw”)

I. This module is for optical burst switching networks only.

II. The main function of this module is the bursts reservation and contended

bursts dropping.

III. It has a reservation table storing and managing the incoming control packets and bursts.

IV. When control packet comes, this module decides to reserve the light path for the burst or not. If the burst reservation is permitted, the obsw

module stores the control packet to the reservation table. When the data bursts come, the obsw module decide to let the bursts pass or drop them according to the reservation table.

4.2.7. Optical Burst Wavelength Assignment Module (named “obwa”)

I. This module is only for the optical burst switching networks.

II. The module is responsible for generating control packets and aggregating data bursts.

III. When the data packets come, the obwa module queues them in the burst queue. When the burst length reaches the burst length limit or the queuing timer is expired, the obwa module generates a control packet and sends it to the next-hop switch for configuring the burst reservation.

After sending the control packet, the obwa module sends the data bursts out.

IV. Of course, the obwa module always uses static RWA scheme to

determine which port and which wavelength channel the packets should go to.

4.3. The Work Flow of Our System

4.3.1. Traditional All-optical Networks

I. At the beginning, users have to set the configuration details of routers and switches such as wavelength conversion, RWA scheme, and protection ring assignment.

II. When the packets come to the border router of the optical networks from other sub-networks, the rwa module checks the packets’ destination.

Then the rwa module decides which light path the packets should go to according to the next-hop router IP.

III. The optical header (it is equal to the MAC header in Ethernet.) will be created, and the rwa module will attach optical header to the front of the packets. After this attaching process, the packets will be sent to the opmanage module.

IV. The opmanage module sends the packets to the destined op module.

V. When the packets go down to the op module, the module will send the packets to the destined wavelength channel according to the optical header.

VI. When the packets arrive at the ophy module, the ophy module simulates the bit error, transmission time, and propagation delay. Then the ophy module sends the packets to the next node.

VII. When the packets reach the switch, it will be received by the ophy module, and the ophy module sends the packets up to the osw module.

The osw module will determine which port and which wavelength channel the packets should go to. The osw module sends those packets

down to the lower modules from wa module to ophy module, and the packets go to the next node.

VIII. The step III to step VII will continue until the packets arrive at the destination router port. The packets will be received by the interface module and written into kernel when they reach the destination router.

4.3.2. Optical Burst Switching Networks

I. At the beginning, the users set the setting details of routers and switches such as wavelength conversion, burst length, and reservation scheme.

II. When the packets come to the obwa module from another subnet, the module will assemble them to create a burst. If the timer of burst

gathering is expired or the burst queue is full, the obwa module generates a control packet and sends it to the next-hop switch. After sending the control packet, the data burst is sent.

III. What the op module, ophy module, opmanage module and the osw module do to the packets in optical burst switching networks is the same as those modules do in the traditional all-optical networks.

IV. When the obsw module gets a control packet, it will check the reservation scheme and the reservation table to decide to offer the bandwidth resources for burst transmission or not.

V. The control packet travels through switches to do burst reservation for its own burst. The travel of control packets ends up at the destination router.

VI. When the data burst (packets) comes to the obsw module, the module sends the burst to the osw module or drops it according to the reservation table and the contention drop scheme.

VII. The burst data will reach the destination router if the destined path is all reserved by its control packet. The burst will be dropped in the middle of the burst transferring if reservation is denied by the obsw module in any one of the optical burst switches.

4.3.3. The Scheme of Protection Ring

I. The users have to assign protection rings and set some parameters

manually before the simulation starts. The protection mechanism will not work without these works.

II. At normal time, the traffic goes on the working path.

III. When the working path is broken, the opmanage module senses it from the link failure signal triggered by ophy module. The opmanage module automatically switches the traffic to the protection port when it knows that the working path is failed.

IV. When the packets go to the opmanage module, the opmanage module checks whether the packets come from working path or protection path.

If they come from working path, the module sends the packets to the working path. If they come from protection path or they come from working path but the working port of this switch is broken, the module sends the packets to protection path.

V. The protection ring mechanism is available only in traditional all-optical networks, but it is not available in optical burst switching networks.

Because in optical burst switching networks the transmission of data burst needs to send control packet to each node on the path to the destination to reserve light path for the burst, the changing of light path

caused by protection switching will fail the reservation which is already done. If one of the links on the light path is failed, the data burst has to send control packet again to reserve a new light path for transmission.