Whats so difficult about ISSU

Fri Nov 9 01:22:20 UTC 2012

I know some people here have mentioned good experiences with ISSU on
Nexus.   I don't doubt that it usually works right, but in my latest
experience with upgrading NX-OS on dual-SUP'ed 7k's, it was "hitless"
if, by "hitless", you mean ~20% packet loss while troubleshooting with
TAC before we found that we had to remove and re-apply QoS policies
from every interface.

Also, depending on the update, linecards might have to be reset.

Oliver

-------------------------------------

Oliver Garraux
Check out my blog:  www.GetSimpliciti.com/blog
Follow me on Twitter:  twitter.com/olivergarraux

On Thu, Nov 8, 2012 at 8:00 PM, Kasper Adel <karim.adel at gmail.com> wrote:
> Does that mean they are the only vendor capable of doing this today?
>
> I am interested in the technology behind this if this is something public,
> any ideas?
>
> Thx
>
> On Friday, November 9, 2012, Kenneth McRae wrote:
>
>> I have performed micro code upgrades using ISSU on the Juniper platform.
>>
>> On Thu, Nov 8, 2012 at 4:52 PM, Kasper Adel <karim.adel at gmail.com<javascript:_e({}, 'cvml', 'karim.adel at gmail.com');>
>> > wrote:
>>
>>> What i was asking is full ISSU, even with micro code. I assume between
>>> Major release there will be microcode upgrade most of the time.
>>>
>>>
>>> On Fri, Nov 9, 2012 at 2:48 AM, Phil <bedard.phil at gmail.com<javascript:_e({}, 'cvml', 'bedard.phil at gmail.com');>>
>>> wrote:
>>>
>>> > The major vendors have figured it out for the most part by moving to
>>> > stateful synchronization between control plane modules and implementing
>>> > non-stop routing.
>>> >
>>> > ALU has supported ISSU on minor releases for many years and just added
>>> > support for major releases.
>>> >
>>> > The Cisco Nexus ISSU works well, I've done an upgrade on a 5K switch and
>>> > it was completely hitless.
>>> >
>>> > Juniper and Cisco with the 9K have gone through some hurdles but ISSU is
>>> > actually usable now if the software versions support it.
>>> >
>>> > The main remaining hurdle is updating microcode on linecards, they still
>>> > need to be rebooted after an upgrade.
>>> >
>>> > Phil
>>> >
>>> > On Nov 8, 2012, at 6:22 PM, Kasper Adel <karim.adel at gmail.com<javascript:_e({}, 'cvml', 'karim.adel at gmail.com');>>
>>> wrote:
>>> >
>>> > > Hello,
>>> > >
>>> > > We've been hearing about ISSU for so many years and i didnt hear that
>>> any
>>> > > vendor was able to achieve it yet.
>>> > >
>>> > > What is the technical reason behind that?
>>> > >
>>> > > If i understand correctly, the way it will be done would be simply to
>>> > have
>>> > > extra ASICs/HW to be able to build dual circuits accessing the same
>>> > memory,
>>> > > and gracefully switch from one to another. Is that right?
>>> > >
>>> > > Thanks,
>>> > > Kim
>>> >
>>>
>>
>>