Whats so difficult about ISSU

Fri Nov 9 03:12:12 UTC 2012

Heh you will find vendors avoid using the term hitless.  I can't think of any router which supports ISSU that is truly hitless.  The ASR9K ISSU states it will sustain less than 6 seconds of loss...

ISSU is still rife with caveats and incompatibilities as well if you are doing more advanced things.

Phil

On Nov 8, 2012, at 8:22 PM, Oliver Garraux <oliver at g.garraux.net> wrote:

> 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
> 