Which OS is behind IOS ?

Hello,

is IOS a custom OS or is it based on VXWorks or an other embedded System
like that ?

--
Georg
www.dingler-it.de

Georg Dingler

Georg Dingler wrote:
> Hello,
>
> is IOS a custom OS or is it based on VXWorks or an other embedded System
> like that ?
>

For the "standard" IOS, it is an OS fully designed by Cisco.
For IOS-XR / Modular IOS (ION), it is based on QNX.

Hi Georg,

Cisco IOS has a "monolithic" architecture, which means that it runs as
a single image and all processes share the same memory space.

There is no memory protection between processes, which means that bugs
in IOS code can potentially corrupt data used by other processes.

It also has a "run to completion" scheduler, which means that the
kernel does not pre-empt a running process -- the process must make a
kernel call before other processes get a chance to run.

For Cisco products that required very high availability, such as the
Cisco CRS-1, these limitations were not acceptable.

In addition, competitive router operating systems that emerged 10-20
years after IOS, such as Juniper's JunOS, were designed not to have
these limitations.

Cisco's response was to develop a new version of Cisco IOS called
IOS-XR that offered modularity and memory protection between processes,
lightweight threads, pre-emptive scheduling and the ability to
independently re-start failed processes.

IOS-XR uses a 3rd party real-time operating system microkernel (QNX),
and a large part of the current IOS code was re-written to take
advantage of the features offered by the new kernel -- a massive
undertaking.

But the microkernel architecture removes from the kernel all process
that are not absolutely required to run in the kernel, and executes
them as processes similar to the application processes.

Through this method, IOS-XR is able to achieve the high availability
desired for the new router platform.

Thus IOS and IOS-XR are very different codebases, though related in
functionality and design.

In 2005, Cisco introduced IOS-XR on the Cisco 12000 series platform,
extending the microkernel architecture from the CRS-1 to Cisco's widely
deployed core router.

Recently (in 2006), Cisco has made available IOS Software Modularity
which extends the QNX microkernel into a more traditional IOS
environment, but still providing the software upgrade capabilities that
customers are demanding.

It is currently available on the Catalyst 6500 enterprise switch.

Sincerely,

Brad Reese
BradReese.Com - Cisco Repair
http://www.bradreese.com/cisco-big-iron-repair.htm
1293 Hendersonville Road, Suite 17
Asheville, North Carolina USA 28803
USA & Canada: 877-549-2680
International: 828-277-7272
Fax: 775-254-3558
AIM: R2MGrant
BradReese.Com - Cisco Power Supply Headquarters
http://www.bradreese.com/cisco-power...-inventory.htm

Thank you very much for this information !

PS: Will IOS-XR be available for the smaller Routers or will it only be
available on the high end models ?

Georg

www.BradReese.Com schrieb:
> Hi Georg,
>
> Cisco IOS has a "monolithic" architecture, which means that it runs as
> a single image and all processes share the same memory space.
>
> There is no memory protection between processes, which means that bugs
> in IOS code can potentially corrupt data used by other processes.
>
> It also has a "run to completion" scheduler, which means that the
> kernel does not pre-empt a running process -- the process must make a
> kernel call before other processes get a chance to run.
>
> For Cisco products that required very high availability, such as the
> Cisco CRS-1, these limitations were not acceptable.
>
> In addition, competitive router operating systems that emerged 10-20
> years after IOS, such as Juniper's JunOS, were designed not to have
> these limitations.
>
> Cisco's response was to develop a new version of Cisco IOS called
> IOS-XR that offered modularity and memory protection between processes,
> lightweight threads, pre-emptive scheduling and the ability to
> independently re-start failed processes.
>
> IOS-XR uses a 3rd party real-time operating system microkernel (QNX),
> and a large part of the current IOS code was re-written to take
> advantage of the features offered by the new kernel -- a massive
> undertaking.
>
> But the microkernel architecture removes from the kernel all process
> that are not absolutely required to run in the kernel, and executes
> them as processes similar to the application processes.
>
> Through this method, IOS-XR is able to achieve the high availability
> desired for the new router platform.
>
> Thus IOS and IOS-XR are very different codebases, though related in
> functionality and design.
>
> In 2005, Cisco introduced IOS-XR on the Cisco 12000 series platform,
> extending the microkernel architecture from the CRS-1 to Cisco's widely
> deployed core router.
>
> Recently (in 2006), Cisco has made available IOS Software Modularity
> which extends the QNX microkernel into a more traditional IOS
> environment, but still providing the software upgrade capabilities that
> customers are demanding.
>
> It is currently available on the Catalyst 6500 enterprise switch.
>
> Sincerely,
>
> Brad Reese
> BradReese.Com - Cisco Repair
> http://www.bradreese.com/cisco-big-iron-repair.htm
> 1293 Hendersonville Road, Suite 17
> Asheville, North Carolina USA 28803
> USA & Canada: 877-549-2680
> International: 828-277-7272
> Fax: 775-254-3558
> AIM: R2MGrant
> BradReese.Com - Cisco Power Supply Headquarters
> http://www.bradreese.com/cisco-power...-inventory.htm
>


--
Georg
www.dingler-it.de

Hi Georg,

To further answer your questions, please contact directly:

Mr. Harold Ritter, CCIE No. 4168.

Harold is a network consulting engineer for Cisco Advanced Network
Services.

He is responsible for helping Cisco top-tier customers to design,
implement, and troubleshoot routing protocols in their environment.

He has been working as a network engineer for more than eight years.

Harold's email address:

hritter *at* cisco.com

Georg, hope this helps.

Brad Reese
Cisco Network Engineer Directory
http://www.bradreese.com/network-engineer-directory.htm

When I use cisco IOS all I see is unix customized by cisco

In article < .com>,
"roger t" <> wrote:

> When I use cisco IOS all I see is unix customized by cisco

There's nothing Unix-related in IOS. The original designers came from
DEC, I believe, and patterned its CLI somewhat after TENEX and TOPS-20.
If you're talking about the automatic completion, that's something Unix
adopted from DEC (it first appeared in tcsh, and the "t" is often
considered to stand for TENEX).

--
Barry Margolin,
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
*** PLEASE don't copy me on replies, I'll read them in the group ***

On 26 Sep 2006 20:00:49 -0700, roger t wrote:
> When I use cisco IOS all I see is unix customized by cisco

When I use Cisco IOS all I see is VMS. Don't worry I know
Cisco isn't VMS. I really don't know how you get Unix though.
(???).


--
Linux Home Automation Neil Cherry
http://www.linuxha.com/ Main site
http://linuxha.blogspot.com/ My HA Blog
http://home.comcast.net/~ncherry/ Backup site

In article <barmar->,
Barry Margolin <> wrote:

> In article < .com>,
> "roger t" <> wrote:
>
> > When I use cisco IOS all I see is unix customized by cisco
>
> There's nothing Unix-related in IOS. The original designers came from
> DEC, I believe, and patterned its CLI somewhat after TENEX and TOPS-20.
> If you're talking about the automatic completion, that's something Unix
> adopted from DEC (it first appeared in tcsh, and the "t" is often
> considered to stand for TENEX).

<nitpick>
I believe, from messages from within Cisco on the old
mailing list, that what was implemented was
taken from the Korn shell (ksh) rather than tcsh.
</nitpick>

Sam

On Wed, 27 Sep 2006 10:48:33 +0100, Sam Wilson wrote:
> In article <barmar->,
> Barry Margolin <> wrote:
>
>> In article < .com>,
>> "roger t" <> wrote:
>>
>> > When I use cisco IOS all I see is unix customized by cisco
>>
>> There's nothing Unix-related in IOS. The original designers came from
>> DEC, I believe, and patterned its CLI somewhat after TENEX and TOPS-20.
>> If you're talking about the automatic completion, that's something Unix
>> adopted from DEC (it first appeared in tcsh, and the "t" is often
>> considered to stand for TENEX).
>
><nitpick>
> I believe, from messages from within Cisco on the old
> mailing list, that what was implemented was
> taken from the Korn shell (ksh) rather than tcsh.
></nitpick>

Oh, good point! 'We' (lots of folks) used to bug Cisco to get the
command line editing put in the routers. I prefered to ask Cisco when
they were going to add emacs (the full X version .

--
Linux Home Automation Neil Cherry
http://www.linuxha.com/ Main site
http://linuxha.blogspot.com/ My HA Blog
http://home.comcast.net/~ncherry/ Backup site