Saturday, May 23, 2020

Global STAC Live

I normally don't do product or vendor shilling on this blog. But I've always liked Peter Lankford at STAC, and I think he did a good job with this video:

Yes, it's a funny advertisement, but instead of being just plain funny, it's actually pretty clever. And I don't just mean the jokes.

The Coronavirus has really disrupted professional conferences and events. Many are postponed, some are just plain cancelled. I assumed that STAC would be a casualty, but Peter is trying to make lemonade by making his 2020 summit virtual.

Now it's not like that has never been done before. Zoom has made quite a name for itself by saving the business meeting. (In fact, many meetings that used to be simple phone conferences have mysteriously and inexplicably drifted into Zoom meetings, I'm not sure why.)

So when I first heard that the 2020 summit was going virtual, I was like ho-hum ... another endless series of Zoom presentations. And it got me to thinking, what was going to be lost? The sales-oriented participants will of course miss glad-handing prospective customers. But what about engineers like me?

We'll miss getting together with our smart friends and colleagues that we haven't seen for a while, and maybe being introduced to their smart friends and colleagues for interesting conversation, war stories, and maybe even the occasional brilliant technical insight. Not going to get any of that out of a zoom presentation.

But Peter's video suggests that he was fully aware of that drawback, and he is experimenting with approaches to address it. I'm skeptical that I will be blown away by it, but I'm intrigued enough to give it a go. And whether it turns out revolutionary, or just another chat room, I respect Peter for effort.

Plus, I  just plain like the ad. :-)

UPDATE: June 3

At the end of day 2, I can safely say that the STAC Live event was well done. The speakers did a good job of dealing with the new format, and there were very few technical glitches. The system seemed to scale well.

In particular, it is nice to be able to replay sessions that you missed (or just couldn't pay attention to) the same afternoon. This is a clear *advantage* to this format as compared to a traditional in-person conference.

The technical content was also very good, but that's not what I want to talk about.

I'm a little sad to report that the social aspect turned out worse than I had hoped. It's not STAC's fault, nor the fault of Ubivent, the technology behind the virtual event. It's the fault of human nature.

When I travel to a venue to attend a function, I am engaged with the event. Yes, I sometimes check email, and will even sometimes hide in a corner to do an important call. But >90% of my time is spent being fully engaged with the people, both in and out of a session. So conversations happen naturally and productively. You get introduced to new people with similar interests. I made a very good friend at a conference a few years ago, just because I was there.

During STAC Live, the chat feature was there, but wasn't used very much. And like all chats, I might type something, and minutes would go by before the response came back. Why? BECAUSE WE'RE ALL BUSY, THAT'S WHY! During an in-person event, we are mostly engaged with our surroundings, but when attending remotely, we are balancing the virtual event with work. And work usually wins. And working from home means there's also family members and pets who need attention.

So even if the event technology were somehow more conducive to socializing, the attendees were not.

So, overall STAC was a good event, better than it had any right to be given the circumstances. And I've already learned some things that I plan to put into practice, so it's been well worth the time. But it being a virtual event does detract something meaningful. And I miss it.

Friday, May 1, 2020

Wireshark: "!=" May have unexpected results

How is it that I haven't sung the praises of Wireshark in this blog? It's one of my favorite tools of all time! I can't get over how powerful it has become.

Occasionally, there are little gotchas. Like when using the "!="  operator, a yellow warning flashes a few times saying:
"!=" may have unexpected results (See the User's Guide)
My first thought: "There's a User's Guide?" My second: "Couldn't you give me a link to it?"

OK, Fine. Here's a direct link to the section "A Common Mistake with !=". The problem is related to "combined expressions", like eth.addr, ip.addr, tcp.port, and udp.port. Those expressions do an implicit "or"ing of the corresponding source and destination fields. E.g. saying tcp.port==12000 is shorthand for:
  (tcp.srcport==12000 || tcp.dstport==12000)

So if you want the opposite of tcp.port==12000, it seems logical to use tcp.port!=12000, thinking that it will eliminate all packets with either source or destination equal to 12000. But you're wrong. It expands to:
  (tcp.srcport!=12000 || tcp.dstport!=12000)
which, doing a little boolean algebra is the same as:
  !(tcp.srcport==12000 && tcp.dstport==12000)
In other words, instead of eliminating packets with either source or destination of 12000, it only eliminates packets with both source and destination of 12000. You'll get way more packets than you wanted.

The solution? Use:
or better yet, expand it out:
  tcp.srcport!= 12000 && tcp.dstport!=12000
I prefer that.

What's So Special About "!="?

It got me to thinking about other forms of inequality, like ">" or "<". Let's say you want to display packets where source or destination (or both) are an ephemeral port:
  tcp.port > 49152
Now let's say you want the opposite - packets where *neither* port is ephemeral. If you do this:
  tcp.port <= 49152
you have the same problem (but this time Wireshark doesn't warn you). This displays all packets that where source or destination (or both) are non-ephemeral.

At the root of all this is the concept of "opposite". With:
  a compare b
you think the opposite is:
  a opposite_compare b
But given the existence of combined expressiions, it's usually safer to use:
  !(a compare b)