參數(shù)資料
型號(hào)： MB86976PF-G
元件分類： 微控制器/微處理器
英文描述： 2 CHANNEL(S), 10M bps, LOCAL AREA NETWORK CONTROLLER, PQFP144
封裝： PLASTIC, QFP-144
文件頁(yè)數(shù)： 11/46頁(yè)
文件大?。?/td> 212K
代理商： MB86976PF-G
MB86976
Fujitsu Microelectronics, Inc.
19
Advanced 11/5/98
the MB86976 deviates from the 802.1d specification in regards to
bridging operations in that frames are not aged. There exists no
mechanism that will timestamp incoming frames to ensure that the
frames are not “obsolete” prior to transmission.
The following steps are performed for each new frame as it is
received from the LAN receive port:
1.
A10-bit hash value (see “Hashing Algorithm” on page 20) is cal-
culated from the 48-bit Destination Address and is used as the
pointer to one of 1024 database “buckets”.
2.
The corresponding “bucket” is linearly searched until a valid
entry containing an identical 48-bit address is found or the end of
the “bucket” is reached. Each bucket may contain up to 8 entries.
3.
If a matching entry is found, the Destination field of the matching
entry is captured.
If no matching entry is found, the Destination field defaults to the
WAN transmit port.
The result of this filtering, along with the results of the (UDLT)
look-up table filtering process, are OR’d together in eliminating
possible destinations of the frame. In the event that either the found
Destination field or the look-up table filtering result is “000,” the
frame is rejected.
Auto-Learning
As new Source Addresses are encountered, they are automatically
added or “l(fā)earned” by the Source Address Database, if space
permits. As entries age, they are periodically removed to make
room for new entries.
Since auto-learned entries in the Source Address Database are
marked with the Destination field set to “000”, the next frame on
the LAN that has this as a destination address will be rejected from
crossing the WAN link. This serves to keep the frame local to the
LAN network.
Static Address Entries
One of the consequences of the auto-learning of Source Addresses is
that entries will periodically expire and need to be re-learned. If a
user wishes to avoid this periodic purging and learning cycle, the
Source Address Database can be configured by the firmware with
static entries.
For example, if the user knows that a given device will always be on
the LAN port of the bridge, its address may be loaded into the
Source Address Database by the firmware. This static filter entry is
identical to that created by the auto-learning process with one
exception - the dynamic field is set to “0” to indicate a static entry.
A static entry is exempt from the periodic purging of the database
and persists until it is removed by the firmware.
Use the following steps to configure the Source Address Database
with a static entry:
1.
Generate a 10-bit hash value using the 48-bit Destination Address
that is to be learned.
2.
Use the hash value as the pointer to one of 1024 database “buck-
ets” and write into the first free location that does not contain a
static entry. The dynamic field must be set to “0,” the valid field to
“1,” and the Destination field to the desired value. In the event
that multiple static entries hash to the same value, the entire
“bucket” may need to be read prior to finding an available free
location
The filtering process using static entries is identical to the filtering
process using dynamic entries. If an ethernet frame comes in with
the same MAC source address as an existing static entry, the static
entry is preserved and the incoming frame is not learned.
Static entries can contain any values for the fields in the header
word, which allows configuring the Source Address Database to
prohibit the transmission of frames to a given remote Destination
Address. Similarily, to allow frames intended for the MB86976 to
reach the processor, the MB86976’s own MAC address (as assigned
by the system developer) should be loaded by firmware into the
source address database with the destination field set to 001 to
forward the frame to the processor in addition to the WAN
transmit port. An appropriate filtering entry in the UDLT is
required to forward frames to the processor alone.
Additonal uses for static entries include allowing frames
containing a multicast address or Bridge Protocol Data Unit
(BPDU) frames to reach the processor. The desired multicast
address or the BPDU address range 0180_C200_0000 to
0180_C200_000F should be loaded into the source address
database with the destination field set to 001.
Source Address Database Maintenance
The Source Address Database requires periodic maintenance in the
form of learning new entries, updating existing entries, and
purging older entries.
Learning New Entries & Updating Existing Entries
As each new frame is received from the LAN port, the following
相關(guān)PDF資料
PDF描述
MB87033BPF SCSI BUS CONTROLLER, PQFP80
MB8867P 21.33 MHz, PROC SPECIFIC CLOCK GENERATOR, PDIP24
MB88R157A OTHER CLOCK GENERATOR, PDSO8
MB89498PMC 8-BIT, MROM, 12.5 MHz, MICROCONTROLLER, PQFP100
MB89F051PMC 8-BIT, FLASH, 12 MHz, MICROCONTROLLER, PQFP64
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MB86977 制造商:FUJITSU 制造商全稱:Fujitsu Component Limited. 功能描述:IP PACKET FORWARDING ENGINE
MB86977PFV-G-BND 制造商:FUJITSU 制造商全稱:Fujitsu Component Limited. 功能描述:IP PACKET FORWARDING ENGINE
MB86A21PMC-G-BNDE1 制造商:FUJITSU 功能描述:
MB86A21PMC-G-JNE1 制造商:FUJITSU 功能描述:
MB86A22PMC-ES-BNDE1 制造商:FUJITSU 功能描述:
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。

采購(gòu)需求

(若只采購(gòu)一條型號(hào)，填寫一行即可)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

*型號(hào) *數(shù)量 廠商 批號(hào) 封裝
添加更多采購(gòu)

我的聯(lián)系方式

*
*
*