[j-nsp] Upgrade without PCMCIA card?

[Richard A Steenbergen]

On Fri, Dec 21, 2007 at 09:31:30AM -0000, michael.firth at bt.com wrote:
> I think that if you want to run JunOS 7.5 or 7.6 you will have to talk
> to your Juniper support people to see if they can get hold of them for
> you.
> 
> Given that a lot of people seem to be having problems getting JunOS 8.x
> releases to run reliably on older hardware, it may be that eventually
> there will be enough of a build up of pressure for them to make a
> 'legacy JunOS', or similar, available for users of older M5, M10, M20 or
> M40 platforms.

Based on personal experience I suspect you want to run something like 7.4 
rather then 7.6, but I've done no actual analysis on exactly when the 
resource utilization increased. Despite the major version bump, the trend 
that I've noticed is that all the heavy lifting or "infrastructure 
changes" tend to happen in advance of the major version bump, and then the 
changes from say 7.6->8.0 are actually fairly minimal.

Remember that JUNOS versioning/development doesn't follow the same rules 
as, for example, FreeBSD. In FreeBSD, developers do work based on major 
version branches (occasionally porting some of the "simpler" changes back 
to the stable branch) until eventually they swap out the whole branch and 
make the new one the stable branch. JUNOS is very different, its dev 
branches and cycles occur between minor versions, and then the major 
version bumps are largely arbitrary.

Tracing the source of a particular issue by code version can be a 
difficult process. Any given major feature you see released in a 
particular version of code has likely been broken up into many smaller 
components which had to happen first, which have likely been written in 
over several releases, and which may interact with any number of other 
"features" or bugs in complex ways. Also, the feature may well have been 
fully written a version or two earlier than you see it publicly, and 
simply hidden in the CLI/release notes so that insiders interested in or 
driving a particular feature can test it first. It is not safe to assume 
that just because you saw a feature pop up in 7.3 that an issue caused by 
it is not there in 7.2, for example. And remember that whatever code you 
see as the latest and greatest available for download, the developers are 
already writing 2 future versions ahead. :)

So in other words, don't think that 7.6 is going to be the "latest and 
most stable" code from a "7.x branch" (because no such thing exists), or 
that it is in turn going to be significantly different from the 8.0 
release. JUNOS routinely gets major internal changes to its infrastructure 
in the middle of a major version, whenever they see fit. What Juniper 
could do for people with older gear is keep the R4 code (or whatever the 
final bug-fix build is) for older versions accessable on the website, with 
a disclaimer that no new development or fixes are going to occur in this 
branch of code and you run it at your own risk. But they'd rather you just 
buy a new box instead. :)

-- 
Richard A Steenbergen <ras at e-gerbil.net>       http://www.e-gerbil.net/ras
GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)