| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 1824.1 | Here ya are. | CGOU14::DMARLOWE | Have you been HUBbed lately? | Thu Dec 29 1994 14:14 | 52 |
|
Q1: Is this config OK if A+B < 2000m ?
-------------- 10 base 5
!
DR90FA/FL
II
II 10 base FL segment A
II 62,5/125
II
DR90FA/FL
!
-------------- 10 base 5
!
DR90FA/FL
II
II 10 base FL segment B
II 62,5/125
II
DR90FA/FA
!
-------------- 10 base 5
>> You could be OK if the overall length, including the thickwire does
not exceed 2.8KM. However, you have 4 repeaters between the top LAN
and the bottom LAN. You cannot put any repeaters on any LANs as you
are at the maximum of the 5-4-3 rule. You should look at replacing
one of the repeaters with a bridge.
Q2: What is the maximum length of the optical fiber allowed between 2
DECswith900EE with an optical transceiver each (DEFLM-AA)
>> 2KM
Q3: Can i configure the (2) and (3) DEChub900 to have this FDDI ring OK?
The 2 FDDI modules in each DEChub belongs to the same ring but are not
linked by an FDDI backplane link in the DEChub900. This is a logical
ring on a linear infrastructure.
DH900(1) DH900(2) DH900(3) DH900(4)
DS900EF---------DS900EF---------DC900MX---------DS900EF
DS900EF---------DS900EF---------DC900MX---------
DC900MX
>> If the 2 modules in each hub are part of the same ring, how are you
going to connect them together? If you are looking to have 2 separate
FDDI "wrapped" rings then OK, just use the front panel ports on all the
modules. If they are to be part of the same ring then the modules in
each hub should be connected via FDDI in the backplane.
dave
|
| 1824.2 | THANKS + OTHER QUESTIONS ? | MARS03::THOMAS | | Fri Dec 30 1994 02:19 | 43 |
|
Thank you for your answers.
For Q1:
What do you mean by the 5-4-3 rule ?
I think that i can put repeaters on the LAN in the middle but no
other repeater on the TOP and BOTTOM LAN. OK ?
If some of these 3 coax segments are 10 base 2, is the rule <2800m
still OK ?
For Q3:
ALL the modules of all DEChub will be part of the same FDDI because the
ring will be like that.
FDDI DH900(1) DH900(2) DH900(3) DH900(4)
in !--DS900EF---------DS900EF---------DC900MX---------DS900EF
back !--DS900EF !-----DS900EF---------DC900MX---------!
plane!--DC900MX---!
The ring is wrapped inside the DH900(1).
There is no FDDI in the backplane of DH900 (2), (3) and (4).
This configuration will be used only for a few monthes. After the
logical FDDI ring will map a physical ring.
I think that this configuration is going to work properly.
OK ?
Thanks for the answers.
Regards,
Bernard THOMAS
ring because a
|
| 1824.3 | ...Just an observation | NETCAD::BATTERSBY | | Fri Dec 30 1994 09:54 | 11 |
| I've noticed a growing number of notes mentioning the DECswitch
900EE and FDDI in the same context. Like Norm Abrams says on his
PBS carpentry program, "let me reassure you", there is no FDDI
circuitry inside the DECswitch 900EE. :-) There is only circuitry
to make FDDI connections in the DECswitch 900EF and PEswitch 900TX.
The DECswitch 900EE is an *Ethernet only* switch (2 AUI, & 4 UTP).
Keep in mind that if you use a pair of DELFM MAU's to link two 900EE's
this fiber link will only run at the wire speed of the interface of the
10baseT UTP ports IE: 10mhz that the MAUs are connecting.
Bob
|
| 1824.4 | Clairification | CGOU14::DMARLOWE | Have you been HUBbed lately? | Fri Dec 30 1994 13:21 | 45 |
|
>> ALL the modules of all DEChub will be part of the same FDDI because the
>> ring will be like that.
>> FDDI DH900(1) DH900(2) DH900(3) DH900(4)
>> in !--DS900EF---------DS900EF---------DC900MX---------DS900EF
>> back !--DS900EF !-----DS900EF---------DC900MX---------!
>> plane!--DC900MX---!
Even though you have represented the FDDI in Hub 1 like HUBWATCH does
it does not work like that. There will be NO ring wrap in Hub 1.
Hub 1 will actually work like this:
<------------------------------------------------ Hub 2
| ------------> Hub 2
| |
---------- ---------- ----------
|A | | | | B| External FDDI
|DC 900MX| |DS 900EF| |DS 900EF| ---------------------
| B| |A B| |A | FDDI in 900 backplane
---------- ---------- ----------
| | | |
--------- --------
>> There is no FDDI in the backplane of DH900 (2), (3) and (4).
Correct.
>> I think that i can put repeaters on the LAN in the middle but no
>> other repeater on the TOP and BOTTOM LAN. OK ?
No. You have 4 repeater between the top LAN and the bottom. No
repeaters can be on any of the thickwire segments. A bridge must
replace a repeater.
>> If some of these 3 coax segments are 10 base 2, is the rule <2800m
>> still OK ?
<=2800M is the max no matter what the media.
dave
|
| 1824.5 | repeater or propagation delay pb ? | MARS03::THOMAS | | Tue Jan 03 1995 03:04 | 12 |
|
I don't understand why i can't put any repeater on the middle LAN.
If for instance, i put a Dec repeater 90 t on the middle LAN, i will
still have less than 4 repeaters between any 2 Ethernet stations.
So why not ?
Is it for propagation delay ?
Regards,
Bernard
|
| 1824.6 | configuration rule ??? | MARS03::THOMAS | | Tue Jan 03 1995 03:51 | 39 |
|
I have just used a DEC configurator tool that has been given to NIS
people. This tool runs on PC. I don't remember its name.
I drew a network like my Q1 question and i changed some coaxial
cable length or optical cable length.
With this configurator tool, i find these result/rules:
* We have a budget of about 4 200 m of optical fiber for the
propagation delay rule,
* A DR90 FL alone can have 2 fiber optical of 2km each,
DR90FL
! !
2km ! !
! !
S1 S2
* A DR90 FL/FA is equivalent to 200 m of optical fiber.
* 500 m of coaxial cable is equivalent to 800 m of optical fiber.
Are this result/rules rigth ?
If they are right, my Q1 network will not work with 500 m coaxial
segments, because the equivalent length in optical fiber will be:
800 + 200 + 1000 + 200 + 800 + 200 + 1000 + 200 + 800 = 5 200 m
OK ?
Regards,
Bernard
|
| 1824.7 | 2 out of 3 ain't bad. | CGOU14::DMARLOWE | Have you been HUBbed lately? | Tue Jan 03 1995 13:49 | 31 |
|
>> I don't understand why i can't put any repeater on the middle LAN.
Sorry, I was a little brain dead a few days ago. Yes you can put
repeaters on the middle LAN. However, repeaters cannot be put on
either the top or bottom LAN. Breaking up the LAN with one or more
bridges would be the best way to go.
>> We have a budget of about 4 200 m of optical fiber for the
propagation delay rule,
Do you mean 2000 instead of 200? If its 200M and not 2000M then you
are OK.
>> A DR90 FL alone can have 2 fiber optical of 2km each,
True, but you cannot put 2KM off 2 ports on the DR 90FL and expect it to
work reliably. This would give you a repeated LAN length of 4KM + 200M
which is a tad over the 2.8KM allowed. Strange things like late
collisions will plague the network.
Planning a network strickly based on timing will allow you to place 5,
6, 7 or more repeaters in line on a LAN without any bridges. However,
network people at customer sites do change and anyone taking over the
LAN had better know the network cold and have all the tools to
calculate delays at a moments notice. Otherwise some user, just by
adding a repeater or 30 feet of coax, could take down the entire network.
The 5-4-3 rule is conservative but generally more forgiving.
dave
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