Which OS is behind IOS ?

Hello,

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

Reply to
Georg Dingler
Loading thread data ...

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

Reply to
Christophe Fillot

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

formatting link
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
formatting link

Reply to
www.BradReese.Com

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

formatting link
schrieb:

Reply to
Georg Dingler

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

formatting link

Reply to
www.BradReese.Com

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

Reply to
roger t

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).

Reply to
Barry Margolin

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. (???).

Reply to
Neil Cherry

I believe, from messages from within Cisco on the old snipped-for-privacy@spot.colorado.edu mailing list, that what was implemented was taken from the Korn shell (ksh) rather than tcsh.

Sam

Reply to
Sam Wilson

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 :-).

Reply to
Neil Cherry

Since I didn't say that it was taken from tcsh, your "rather than" doesn't really make sense. I said that Cisco got it from DEC (maybe it was VMS rather than TENEX/TOPS-20), not from any Unix source.

The most obvious way that IOS differs from Unix is the lack of "-" to introduce command options. On the other hand, there are a few commands that use /option:value, a very VMS-ish thing.

Reply to
Barry Margolin

Reply to
Pirke

:-) How nitpicky do you want to get? I concede that you didn't say Cisco got the command completion from Unix, however since it did come from ksh then in fact they DID get it from Unix. If you really want to get picky then your parenthetical comment about it first appearing in tcsh is only true for Unix since it had previously appeared in TENEX.

A very DEC thing in general - I was a relatively late user of DEC OSs - TOPS-10 and various stuff on PDP-8s in the late 1970s, and RT-11 in the early 80s, by which time CP/M had also borrowed the command names and syntax.

Sam

Reply to
Sam Wilson

Every history I have ever read of Cisco says that the two original founders were long-time Stanford DECSystem-10/DECSystem-20 hackers (and perhaps PDP-6 as well), which would make sense since Stanford in that era was a fanatical bastion of 36-bit Digital systems. After cashing out one of the Cisco founders want on to fund XKL which for a while was building new DEC-10 compatibles running a clone of TOPS-10.

TOPS-10 hackers in particular found Unix(tm) sort of amusing in a pat-the-little-brother-on-the-head way, and I doubt that when starting out to create a new CLI that any Unix variant would have been the basis of choice.

sPh

Reply to
sphealey

I had no idea what DEC was. Thanks to the users who pointed DEC out and for the history lesson.

formatting link
this article confirms what you guys are saying. Roger Thompson

Reply to
roger t

Cabling-Design.com Forums website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.