Re: Clock Rate

I DONT agree to you last point .

U have male and female parts in smart serial cables .

Just take following example :

CAB-SS-V35MT and CAB-SS-V35FC

The ends that goes in WIC / HWIC card is the same ..(atleast physically
they look the same)
But the other end of cable definatly is a male/female .

HTH
Gaurav Madan

On Mon, Jul 18, 2011 at 9:42 PM, Carlos G Mendioroz <tron_at_huapi.ba.ar>wrote:

> GAURAV MADAN @ 18/07/2011 11:52 -0300 dixit:
>
> Agreed ..
>> wahtever you told is correct ! thats what a clocking and a DCE end means .
>>
>> Whatever I told was from Cisco point of view and how things work in cisco
>> routers environment . Hence what i meant was that cisco routers only act
>> as
>> DCE .(providing clock)
>>
>
> I don't think this is right. Routers (including cisco's) are DTEs.
> Their ability to provide clock do not make them DCEs, even if we
> call them so. But this is semantic.
>
>
> As far as your last point is concerned ; Cisco does sell the cables with
>> one
>> end as DCE and other end as DTE . In fact all the SS (smart serial) cables
>> have a Male part and a female part (connector in middle) and hence have a
>> DCE end and a DTE end .
>>
>
> This is confusing. There's only one gender for SS cables, and I would say
> they are "male". If that is the case, a DTE cable has two males,
> and a DCE cable has one of each. Note that a "DTE" cable is one that
> signals the router to behave as a DTE.
>
> The cables I was referring to have two SS connectors.
>
> -Carlos
>
>
>
>
>> Thnx
>> Gaurav Madan
>> CCIE
>>
>> On Mon, Jul 18, 2011 at 3:35 PM, Carlos G Mendioroz <tron_at_huapi.ba.ar
>> >wrote:
>>
>> Gaurav,
>>> I would like to share my understanding of what clock is.
>>> I guess it should be clear that clock rate is of no use in
>>> dynamips and its clients (dynagen/GNS3), as no phy layer
>>> emulation takes place there, and data is transferred using
>>> UDP between interfaces.
>>>
>>> When you have an asynchronous link, the bits timing is recognized
>>> on each byte boundary in an independent way. Each byte is independent of
>>> the previous, and there is no out of band reference between Tx and Rx.
>>> This is expensive in terms of time, because you need start bits and
>>> stop bits.
>>>
>>> So in synchronous links, a reference timing is kept at the endpoints
>>> to be reused for all bits/bytes. DCE's do that (recover the clock)
>>> and share it via an out of band signal with the DTE. Each side of
>>> a serial link is supposed to have a DCE and a DTE.
>>>
>>> So routers (DTEs) should actually use clock info from its associated DCE.
>>> Routers has no business in clocking.
>>>
>>> But we sometimes use routers connected back to back, and we don't want
>>> to set up DCEs, so we use sort of null modems, thanks to the ability
>>> of routers to fake being a DCE to the linked router. This faking implies
>>> the provision of a clock reference, hence the clock rate command, and
>>> a specially wired cable that connects a clock source pin on the smart
>>> connector to the pin used by DCEs to provide the clock. What we call
>>> a DCE cable. Routers recognize the presence of such cable (that's why
>>> we call them smart cables I guess :) and enable the clocking.
>>>
>>> Last, some actually use cables that combine a DTE cable and a DCE
>>> cable, becoming real "null modems". Those cables do have a DCE end
>>> and a DTE end indeed. AFAIK, cisco does not sell such cables, but
>>> they are handly in labs.
>>>
>>> HTH,
>>> -Carlos
>>>
>>>
>>> GAURAV MADAN @ 17/07/2011 11:35 -0300 dixit:
>>>
>>> :)))))
>>>>
>>>> DTE , DCE are devices (routers in your case) each having defined purpose
>>>> .
>>>>
>>>> But you need to plug in right cable to right device .
>>>> Physically a serial WIC / HWIC card plugged in a router can assume a
>>>> role
>>>> of a DTE as well as DCE.
>>>> It depends on the cable that is connected to serial interface that the
>>>> end
>>>> takes a role of DCE or a DTE .
>>>>
>>>> Each serial cable type (RS 232 , V.35 , 449 , 530 etc etc) have a DTE
>>>> end
>>>> and a DCE end ; so depending on what is plugged in where .. the end is
>>>> defined .
>>>>
>>>> Hope some clarity this time ,
>>>>
>>>> Gaurav Madan
>>>> CCIE .
>>>>
>>>> On Sun, Jul 17, 2011 at 7:05 PM, Carlos G Mendioroz <tron_at_huapi.ba.ar
>>>> <mailto:
>>>> tron_at_huapi.ba.ar>> wrote:
>>>>
>>>> This is getting so distant from reality ... as a lab can get.
>>>> What exactly is DCE and DTE ? Is a router a DTE or a DCE ?
>>>> Is the cable a DCE or a DTE ? :)
>>>> -Carlos
>>>>
>>>> Radioactive Frog @ 17/07/2011 01:57 -0300 dixit:
>>>>
>>>> Great explaination Gaurav.
>>>> Just would add on top of gaurav's statement - You need a very
>>>> SPECIFIC
>>>> cables that has one end DTE and other end DCE to get it working.
>>>>
>>>> On Sun, Jul 17, 2011 at 2:12 AM, GAURAV MADAN
>>>> <gauravmadan1177_at_gmail.com
>>>> <mailto:gauravmadan1177_at_gmail.****com <gauravmadan1177_at_gmail.com>
>>>>
>>>> __wrote:
>>>>>>
>>>>>
>>>> Things to consider here are :
>>>>
>>>> 1) Clock rate is applicable to DCE devices and not on DTE
>>>> devices
>>>> 2) Devices can be categorized as DCE or DTE depending the
>>>> cable connected
>>>> to
>>>> serial interface.
>>>> 3) Generally DCE devices are FR switch etc.
>>>> 4) If you are configuring the back to back connection ;
>>>> configure "clock
>>>> rate <> " CLI on DCE end only
>>>> 5) I think latest IOS on serial HWIC will take clock rate
>>>> command only on
>>>> DCE end and not on DTE end . However older IOS used to take
>>>> it on any
>>>> device
>>>> 6) Any rate is good ... as long as it is working .. default
>>>> 9600 bps should
>>>> be OK .
>>>>
>>>>
>>>> HTH
>>>> Gaurav Madan
>>>> CCIE
>>>>
>>>> On Sat, Jul 16, 2011 at 9:36 PM, <jhnrose401_at_gmail.com
>>>> <mailto:jhnrose401_at_gmail.com>> wrote:
>>>>
>>>> Dear
>>>>
>>>> I want to know what clock rate i will use when i am in
>>>> the lab or when i
>>>>
>>>> am
>>>>
>>>> using
>>>> dynamips what is the method or way i will configure
>>>> the correct clock
>>>> rate to
>>>> my routers
>>>>
>>>> Eg
>>>>
>>>> For DCE i ll configure the clock rate not for DTE correct
>>>>
>>>> if both devices are DCE i will define CR on both or in a
>>>> single devices.
>>>>
>>>> R1 --ser1/0 -------------------s1/0 R2
>>>>
>>>> I am facing problem my ospf adj flap after few minutes
>>>> is CR are the
>>>>
>>>> reason
>>>>
>>>> R1 = s1/0 ip add 10.1.1.1/24 <http://10.1.1.1/24> and
>>>> loop back 1.1.1.1/24 <http://1.1.1.1/24>
>>>> R2 = s1/0 ip add 10.1.1.2/24 <http://10.1.1.2/24> and
>>>> loop back 2.1.1.1/24 <http://2.1.1.1/24>
>>>>
>>>> clock rate 64000 on both sides
>>>> R1 and R2
>>>>
>>>> router ospf 1
>>>> net 0.0.0.0 255.255.255.255 are 0
>>>>
>>>> thks
>>>>
>>>>
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>>>>
>>>>
>>>>
>>>>
>>>> -- Carlos G Mendioroz <tron_at_huapi.ba.ar <mailto:tron_at_huapi.ba.ar
>>>> LW7 EQI Argentina
>>>>
>>>>
>>>>
>>>> --
>>> Carlos G Mendioroz <tron_at_huapi.ba.ar> LW7 EQI Argentina
>>>
>>
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>>
>>
> --
> Carlos G Mendioroz <tron_at_huapi.ba.ar> LW7 EQI Argentina

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Received on Mon Jul 18 2011 - 22:14:10 ART