DLINK Q:Is Auto-Negotiation a standard? A:Auto-Negotiation is a technology standard that defined by the IEEE 802.3u 100BASE-T Working Group for a mechanism to adapt multi-speed network devices. Currently, the Auto-Negotiation mechanism is defined in Clause 28 of the D5 draft of the ANSI/IEEE Std 802.3 MAC Parameters, Physical Layer, Medium Attachment Units and Repeater for 100 Mb/s Operation. This draft has been approved by the IEEE 802.3 Working Group. Q:What is Auto-Negotiation? A:Auto-Negotiation is a mechanism that takes control of the cable when a connection is established to a network device. Auto-Negotiation detects the various modes that exist in the device on the other end of the wire, and advertises it own abilities to automatically configure the highest performance mode of interoperation. Auto-Negotiation acts like a rotary switch that automatically switches to the correct technology, such as 10BASE-T, 100BASE-TX, 100BASE-T4, or a corresponding Full Duplex mode. Once the highest performance common mode is determined, Auto-Negotiation passes control of the cable to the appropriate technology and becomes transparent until the connection is broken. Auto-Negotiation leverages the proven link function of 10BASE-T to provide robust operation over Category 3, 4, or 5 Unshielded Twisted Pair (UTP.) Q: What are the benefits of Auto-Negotiation? A:- AUTOMATIC CONNECTION The primary benefit of Auto-Negotiation is the automatic connection of the highest performance technology available without any intervention from a user, manager, or management software. - BACKWARDS COMPATIBILITY If Auto-Negotiation exists at only one end of a twisted-pair link, it finds that the Link device does not support the Auto-Negotiation mechanism. Instead of exchanging configuration information, it examines the signal it is receiving. If Auto-Negotiation discovers that the signal it is receiving. If Auto-Negotiation that the signal matches a technology that the device supports that the signal matches a technology that the device supports, it will automatically connect that technology. This function, know as Parallel Detection, gives Auto-Negotiation the ability to be compatible with any device that does not support Auto-Negotiation, yet support: 10BASE-T, 100BASE-TX, or 100BASE-T4, Connection to any technology by Parallel Detection other than those listed above is not supported by Auto-Negotiation. - NETWORK PROTECTION If there is no common technology exists, Auto-Negotiation will not make a connection. This assures preservation will not make a connection. This assures preservation of network integrity and minimization of network down time. In particular, Hubs are a primary beneficiary of this feature. For example, if a user connected through that switch. However, if the hub has Auto-Negotiation, it would refuse the connection and allow the rest of the networks to continue as usual. In fact, with Auto-Negotiation in the hub, the network users are protected from any connection that the hub cannot recognize of accept. - UPGRADE PATH New nodes on the market will have 100Mb/s functionality also traditional 10BASE-T. This means that there will be some latent performance available as these new nodes are added to an old 10BASE-T network. When the performance issue becomes critical, the latent ability can be tapped into by upgrading the hub. Auto-Negotiation enables the upgrade to occur without reconfiguring each node and/or each port on the new hub. Q:How many situations of Auto-Negotiation? A:There are two basic cases that Auto-Negotiation accounts for as shown following. 10BASE-T/100BASE-TX Switch with Auto-Negotiation 旼컴컴컴컴컴컴� 旼컴컴컴캑 Hub 쳐컴컴컴커 旼컴컴좔컴커 읕컴컴컴컴컴컴� 旼컴컨컴컴커 � Node A � � Node B � 읕컴컴컴컴켸 읕컴컴컴컴켸 100BASE-TX/10BASE-T 10BASE-T Auto-Negotiation 1. Auto-Negotiation exists at both ends of a twisted-pair link. (Node A to hub) Auto-Negotiation is most useful if it exists at both ends of the link since both ends speak the same "language" at start up. This allows a rich set of information to be transferred. 2. Auto-Negotiation exists at only one end of a twisted-pair link. (Node B to hub) The key to Auto-Negotiation's interoperation with installed, legacy LANs are the Parallel Detection function. The Parallel Detection function accounts for the case where only one end or a twisted-pair link has Auto-Negotiation. For example, consider an installed 10BASE-T node connected to a hub that supports 10BASE-T, 100BASE-TX, and Auto-Negotiation (see Figure). Here, the hub recognizes the unique signals that the 10BASE-T only device produces and switches to 10BASE-T operation. Q:How does Auto-Negotiation operate? A:An Auto-Negotiation device advertises its abilities and detects the abilities of the remote device by Fast Link Pluse. Once Auto-Negotiation has received the link device's abilities in this way and it receives acknowledgment that its abilities have also been received by the link device, Auto-Negotiation compares the two sets of abilities and decides which technology to connect. This decision is based upon a preagreed priority of technologies. Auto-Negotiation attaches the highest performance common technology to the medium and becomes transparent until the link goes down or is reset. Q:What is the priority hierarchy of Auto-Negotiation? A:1.100BASE-TX Full Duplex 2.100BASE-T4 3.100BASE-TX 4.10BASE-T Full Duplex 5.10BASE-T Q:How does Parallel Detection operate? A:Auto-Negotiation passes the signals presently on the receiver to the 100BASE-TX and 100BASE-T4 Link Monitor functions. If Auto-Negotiation finds that exactly one Link Monitor function shows that the link is good, then it can connect that technology to the media. Note, however, that this function is only carried out for 10BASE-T, 10BASE-TX, and 100BASE-T4. Future multi-mode devices will use Auto-Negotiation as the basis of automatic mode switching. Auto-Negotiation incorporates a modified 10BASE-T Link Integrity Test function as interoperate properly with installed 10BASE-T devices. The modifications ensure that Auto-Negotiation can control the function such that 10BASE-T devices are always correctly detected.