Auto-negotiation is a requirement for using 1000BASE-T according to IEEE standard. Gigabit Ethernet needs link auto-negotiated to determine master and slave association pair. Without auto-negotiation, the link clock will not form properly and underlying physical problem can occur. Due to this reason, Packetshaper is following IEEE standard to ensure properly Gigabit Ethernet connections. Following are extract from IEEE standard on 1000BASE-T.
All 1000 BASE-T PHYs shall provide support for Auto-Negotiation (Clause 28) and shall be capable of operating as MASTER or SLAVE. Auto-Negotiation is performed as part of the initial set-up of the link, and allows the PHYs at each end to advertise their capabilities (speed, PHY type, half or full duplex) and to automatically select the operating mode for communication on the link. Auto-negotiation signaling is used for the following two primary purposes for 1000BASE-T:
a) To negotiate that the PHY is capable of supporting 1000BASE-T half duplex or full duplex transmission.
b) To determine the MASTER-SLAVE relationship between the PHYs at each end of the link. 1000BASE-T MASTER PHY is clocked from a local source. The SLAVE PHY uses loop timing where the clock is recovered from the received data stream.
Some vendors are providing the option of manual setting the speed of gigabit interface.Since this is not defined in the IEEE 802.3ab standard, it is only recommended to manually set the interfaces when connecting to the same vendor products to prevent vendor incompatibility issues.
Imported Document ID: 000016500
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