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參數(shù)資料
| 型號： | RTL8305SB |
| 英文描述： | RTL8305SB |
| 中文描述： | RTL8305SB |
| 文件頁數(shù)： | 38/66頁 |
| 文件大小： | 963K |
| 代理商： | RTL8305SB |
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RTL8305SB
2002/04/09
38
Rev.1.0
7.1.6 Address Search, Learning and Aging
When a packet is received, the RTL8305SB will first use the least 10 bits of the destination MAC address to index the
1024-entry look-up table and at the same time will compare the destination MAC address with the contents of the 16-entry
CAM. If the indexed entry is valid or the CAM comparison is match, this received packet will be forwarded to the
corresponding destination port. Otherwise, the RTL8305SB will broadcast the packet. This is called ‘search’.
The RTL8305SB then extracts the least 10 bits of source MAC address to index the 1024-entry look-up table. If this indexed
entry is empty, it will record the source MAC address and update switching information. If this is an occupied entry with the
same switching information, it will update the entry with new information. This is called ‘learning’. If the indexed location has
been occupied by different MAC address (hash collision), the new source MAC address will be recorded into the 16-entry
CAM. The 16 entry CAM can reduce the address hash collision and will improve the switch network performance.
Address aging function is used to keep the contents of the address table correct in a dynamic network topology. The look-up
engine will update time stamp information of an entry whenever the corresponding source MAC address appears. An entry
will be invalid (aging out) if it’s time stamp information is not refreshed by the address learning process during the aging time
period. Aging time of the RTL8305SB is around 200 to 300 seconds.
7.1.7 Address Direct Mapping Mode
The RTL8305SB uses the least 10 bits of the MAC address to index the 1024-entry look-up table. For example: the index of
MAC address “12 34 56 78 90 ab” will be 0ab.
7.1.8 Half Duplex Operation
In half duplex mode, the CSMA/CD media access method is the means by which two or more stations share a common
transmission medium. To transmit, a station waits (defers) for a quiet period on the medium (that is, no other station is
transmitting) and then sends the intended message in bit-serial form. If, after initiating a transmission, the message collides
with that of another station, then each transmitting station intentionally transmits for an additional predefined period to ensure
propagation of the collision throughout the system. The station remains silent for a random amount of time (backoff) before
attempting to transmit again.
When a transmission attempt has terminated due to a collision, it is retried until it is successful. The scheduling of the
retransmissions is determined by a controlled randomization process called “truncated binary exponential backoff” At the end
of enforcing a collision (jamming), the switch delays before attempting to retransmit the frame. The delay is an integer
multiple of slotTime (512 bit times). The number of slot times to delay before the n
th
retransmission attempt is chosen as a
uniformly distributed random integer r in the range:
0
≦
r < 2
k
where
k =min (n, backoffLimit), The 802.3 defines the backoffLimit as 10.
7.1.9 Inter-Frame Gap
The Inter-Frame Gap is 9.6μs for 10Mbps Ethernet and 960ns for 100Mbps Fast Ethernet.
7.1.10 Illegal Frame
Illegal frames such as CRC error packets, runt packets (length < 64 bytes) and oversize packets (length > maximum length)
will be discarded.
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相關(guān)代理商/技術(shù)參數(shù) |
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|---|---|
| RTL8305SC | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:用于100M網(wǎng)絡(luò)交換 |
| RTL8305SC-LF | 制造商:Realtek Semiconductor 功能描述: |
| RTL8308B | 制造商:Realtek Semiconductor 功能描述:8-PORT 10/100 ETHERNET SWITCH CONTROLLER WITH EMBEDDED MEMORY, PQFP128 |
| RTL8309SB | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:SINGLE-CHIP 9-PORT 10/100MBPS SWITCH CONTROLLER |
| RTL8309SB-LF | 制造商:Realtek Semiconductor 功能描述:RTL8309 Series 9 Port 10/100 Mbps Ethernet Switch Controller - PQFP-128 制造商:Realtek 功能描述:RTL8309 Series 9 Port 10/100 Mbps Ethernet Switch Controller - PQFP-128 |
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