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Auto-Negotiation

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Auto-Negotiation

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    1. Auto-Negotiation This is good stuff folks. By Matthew Hersh

    3. Auto-Negotiation What is ANEG? Some devices support more than one speed, i.e. 10BASE-T and 100BASE-TX. A device that supports multiple speeds and/or duplex’s needs a mechanism to decide what speed and duplex to link at. ANEG is that mechanism.

    4. The two islands Lets look at an example. Two men are stranded on two different islands. Each one is very lonely and wants to talk to someone. So one day the first man “James” carves a note into a piece of bark and throws it into the ocean. To his great surprise and excitement many days later a piece of bark floats onto his beach, but when he picks it up, the note he finds is in a different language. This is just a quick overview of the arbitration process. Basically both devices will transmit their base page, then if both device support next page, indicated by the next page bit they send a next page, and repeat until all the pages are complete before sending signaling. This is just a quick overview of the arbitration process. Basically both devices will transmit their base page, then if both device support next page, indicated by the next page bit they send a next page, and repeat until all the pages are complete before sending signaling.

    5. The two islands James isn’t about to give up, so he sits down and tries to figure out a way to communicate, first he decides they need to speak the same language, but he doesn’t know what language(s) his friend speaks. While he is thinking a second piece of bark floats onto the beach. He looks at it and finds that is identical to the first one, so he still can’t read it, but he realizes that the man he is talking to is very smart. By throwing more than one piece of bark with the same note, it increased that chance that he would receive it This is just a quick overview of the arbitration process. Basically both devices will transmit their base page, then if both device support next page, indicated by the next page bit they send a next page, and repeat until all the pages are complete before sending signaling. This is just a quick overview of the arbitration process. Basically both devices will transmit their base page, then if both device support next page, indicated by the next page bit they send a next page, and repeat until all the pages are complete before sending signaling.

    6. The two islands So now James starts to carve a new note. He writes down each of the languages he can speak, and if he speaks it fluently or not. Then he copies it many times and throws them into the ocean. Days later, he starts to get pieces of bark back. His friend had gotten the idea, and all of these pieces of bark listed the languages his friend could speak. So he circled a language they could both speak fluently and threw them back into the ocean. This is just a quick overview of the arbitration process. Basically both devices will transmit their base page, then if both device support next page, indicated by the next page bit they send a next page, and repeat until all the pages are complete before sending signaling. This is just a quick overview of the arbitration process. Basically both devices will transmit their base page, then if both device support next page, indicated by the next page bit they send a next page, and repeat until all the pages are complete before sending signaling.

    7. The two islands The next piece of bark he received was a hello note from his new friend “Chris” in a language that he could read, and from then on they were great pen pals. This is just a quick overview of the arbitration process. Basically both devices will transmit their base page, then if both device support next page, indicated by the next page bit they send a next page, and repeat until all the pages are complete before sending signaling. This is just a quick overview of the arbitration process. Basically both devices will transmit their base page, then if both device support next page, indicated by the next page bit they send a next page, and repeat until all the pages are complete before sending signaling.

    8. Transmissions A device will always be sending stuff, even when not connected to another device. If the device only supports one speed/duplex combo, then the device will be transmitting link signaling according with that speed (Does not support ANEG – Legacy device). If the device supports more than one speed (or duplex), then the device will be transmitting FLPs (Does Support ANEG).

    9. Copper ANEG (NLPs) This is a 10BASE-T LTP (link test pulse) It exactly matches an NLP (normal link pulse) sent by an Auto-Negotiating device

    10. Copper ANEG (FLPs) What is an FLP? An FLP is a Fast Link Pulse. It is a 16-bit code word that is transmitted through a burst of electronic pulses. An FLP has 17 “clock” pulses(NLPs). If there is a pulse between two clock pulses, then that pulse is considered a “data” pulse. Since there are 17 clock pulses, there are 16 possible data pulses, which is how the FLP is a 16 bit code word.

    11. Copper ANEG (FLPs) Since FLPs are 16-bit code words, that means that there are 16 bits that can be either one or zero. Each bit represents a capability that the DUT can or cannot support.

    12. Copper ANEG – Base Page All Auto-Negotiating devices transmit a Base Page to determine link partner capabilities. The Base Page is a series of transmitted FLPs that are identical. The Base Page is broken down as follows: Bits 0-4, Selector Field Combination – defines what technology is being used. Bits 5-11, Technology Ability Field – defines what capabilities are supported by the DUT. 10BASE-T full and half duplex, 100BASE-TX full and half duplex, 100BASE-T4, PAUSE, and ASM_DIR PAUSE are all possibilities that a device can advertise in the Technology Ability Field of its Base Page. Bit 12 – Recently defined as “Extended Next Pages” bit, intended for use with 10GBase-T. Bit 13 – Remote Fault Bit Bit 14 – Acknowledge Bit Bit 15 – Next Page Bit

    13. Copper ANEG – Base Page A device will set any of the bits in the Base Page that the device actually supports. If a device wants to indicate 1000BASE-T capabilities, the next page bit must be set because 1000BASE-T links can only be established through a Next Page Exchange. There are two types of Next Pages: Message Page and Unformatted Page.

    14. Copper ANEG - Next Pages A device will support a Next Page Exchange usually if it has additional information that it wants to transmit (i.e. 1000BASE-T capabilities). If the device wants to indicate 1000BASE-T capabilities, the first Next Page it will send is a Message Page.

    15. Next Pages – Message Page A device can indicate a Next Page to be a Message Page by setting the Message Page bit (bit 13). The Message Page will contain a code number. This code number corresponds to the reason for going through a Next Page Exchange. A message code 8, for example, indicates that the device wants to attempt a 1000BASE-T link and that two Unformatted Next Pages are following. A message code 1 indicates that it is Null Message Page, and no more information needs to be transmitted.

    16. Next Pages – Unformatted Page Contains 11 bits of information Contents of these pages can be defined by previous message pages. When a message code 8 had already been sent, the first Unformatted Page following the message page would contain the 1000BASE-T capabilities. This also includes Master/Slave bits. The second Unformatted Page in a 1000BASE-T Next Page Exchange contains a seed value which is the last resort to resolve a Master and Slave.

    17. “Bitwise” look at pages This is a bit by bit look at the three types of pages As you can see each is the same 16 bits long, but have slightly different configurations Blue indicates the Base Page, and Yellow indicates Next Pages

    18. Fiber Auto - Negotiation 1000BASE-SX and 1000BASE-LX devices also determine a link using ANEG. These technologies use fiber, so ANEG is different than it is for copper, however the concepts are the same.

    19. /C/ Ordered Sets Fiber ANEG still uses 16-bit code words. It also has a Base Page, but instead of using FLPs, it uses /C/ ordered sets. ANEG coordinates with the PCS to decide what to send. If ANEG is restarted, ANEG temporarily takes control of the PCS. While the device is ANEGing, ANEG tells the PCS what to transmit within the /C/ ordered set. When a link is established, the PCS takes control and transmits /I/ ordered sets and/or packets. Synchronization required before ANEGing. Synchronization required before ANEGing.

    20. /C/ Ordered Sets /C/ ordered sets contain the following abilities: 1000BASE-X full and half duplex PAUSE settings Remote Fault Next Page

    21. Fiber ANEG – Next Page Devices can call for a Next Page Exchange, however, it is not required and rarely implemented.

    22. “Bitwise” look at the Page This is a bit by bit look at the Base Page for Fiber ANEG.

    23. Copper ANEG vs. Fiber ANEG The major issue between copper and fiber ANEG is where each is located in OSI stack. For copper, ANEG is located below the PMA. This means that the ANEG process can occur before signaling is transmitted For fiber, ANEG is located in the PCS. This means that two devices must transmit signaling before ANEG can be done What this means is that copper ANEG can be used for multiple speeds that use difference signaling techniques, while fiber ANEG can only be used for 1000BASE-X devices.

    24. OSI location

    25. OSI Location

    26. Priority Resolution When two devices are connected, before they actually establish a link, they send information back and forth to determine what each device supports. There is an order of speed/duplex combinations in which every device should follow. This is called Priority Resolution. Once all information is transmitted, a link should be established according to the Priority Resolution.

    27. Copper Priority Resolution 1000BASE-T full duplex 1000BASE-T 100BASE-T2 full duplex 100BASE-TX full duplex 100BASE-T2 100BASE-T4 100BASE-TX 10BASE-T full duplex 10BASE-T

    28. Fiber Priority Resolution 1000BASE-X full duplex 1000BASE-X half duplex 1000BASE-X refers to either 1000BASE-SX or 1000BASE-LX.

    29. Priority Resolution Auto-Negotiating devices that are connected should establish the Highest Common Denominator(HCD) link in accordance with the Priority Resolution.

    30. Parallel Detection Legacy devices only support one speed, and only half duplex at that speed. If an Auto-Negotiating device is connected to a Legacy device, the ANEG device needs a method to detect the type of signaling being received. The link established will be a half duplex link. This method is called parallel detection.

    31. Parallel Detection Some devices can be configured to transmit only one speed. If the other device connected is ANEGing, that device will have to parallel detect to the appropriate speed in order to establish a link. However, in this case, the ANEGing device should always establish a half duplex link, but the manually configured device could be set to full duplex, in which case the link established will be full duplex on one end and half duplex on the other.

    32. Software Much software created by former and current students. Software all written in Labview, a picture oriented programming language. Two main parts to the code: receive, and transmit.

    33. Receive Software

    34. Transmit Software

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