This week, I gave a two hour talk to the Freehold High School Computer Science Academy on how VoIP works. This ended up being quite a bit of work actually, since I needed to distill my existing tutorials to something a high school student could understand. I ended up needing to explain a bunch of core IP concepts first. Here's what I came up with. The feedback from the students was positive - many said they understood it! You can find the PPT here. Comments on the content are most welcome.

IP communications services - voice, video and chat and the many variations therein - are all the rage again. Startups are sprouting daily. Though some focus just on mobile, many are building cross-platform applications.

When building such a service, the first and most important capability that you need to build is perhaps not so obvious. It is not wideband voice. It is not chat. It is automated (and silent) client software upgrade. 

The venerable operating system has been around almost as long as the computer has been in existence. Though the "computer" has changed - from mainframes to PCs and now to mobile devices and tablets - the role of its operating system is largely similar. The OS abstracts the underlying hardware and provides applications access to those hardware services. These services typically include file system access, network access, graphics and sound, and of course memory and compute. These are accessed via APIs provided by the OS.
Cloud provides a new way of writing software, and with it, new tools have emerged that make it easier to write that software. One of the newest ones on the block is the Platform as a Service or PaaS. Vendors of PaaS include Microsoft's Azure, Salesforce's Heroku, Cloud Foundry, and to some degree Amazon's AWS. What is a PaaS? PaaS is the operating system for the cloud. Like a computer OS, a PaaS provides a set of APIs which applications can access to make their lives easier. Whereas a computer OS provides access to the services of a single computer, a PaaS provides access to the services of many, spread across many data centers. Whereas a computer OS provides a software API bound to specific languages, a PaaS provides access to services over a network that is bound to specific on-the-wire protocols - typically REST. 

And just what are these services? Though they vary from provider to provider, these are the five core services which I view as foundational to PaaS:

1. Deployment Automation: The PaaS provides a way to take your code - for example your Java application - and then get it deployed across a number of machines in different data centers in a completely automated fashion. In Heroku, this is done with a git push. Heroku monitors your repo and once you push an update, it extracts it, distributes it to the various machines that will run your code, makes sure the JVM is up and running, and starts your app. Contrast this with AWS (which does not provide this capability). On AWS you can spin up a VM, but they its your job to get your code onto the VMs, make sure the JVM is there, and so on. A PaaS does all of that for you.
2. HTTP Request Routing: PaaS is really tuned around web services. The PaaS will provide its own HTTP reverse proxy, handle DNS configuration, TLS termination, and make sure requests for an HTTP URI are routed to a running instance of your code. As a developer, you no longer need to worry about any of that. Just write your web app, and the platform will get the queries to a running server. 
3. Scale and HA: If you write your app in the right way - namely, using stateless web services that store all persistent state in a shared backend database - the platform can provide scale and high availability. It can turn up as many instances of your app as is needed to handle the incoming request load. It can handle failed machines or server instances, and restart them for you. If a DC fails, through DNS it will route traffic to a backup DC to running instances of your code that are there. The trick to making this magic work is writing your app correctly and doing a good job on your database selection and schema design.
4. Data Storage: The PaaS will also provide databases as a service. This means there are databases up and running that you can access via some kind of protocol interface. This might be RESTful access (as in the case of Amazon S3 or Azure storage services), SQL queries for a relational database, or whatever the query protocol is for a noSQL database. As an application developer, you do not need to set up, run, or configure this database. The PaaS provides it for you. 
5. Application Upgrade/Downgrade: A cloud service needs to always be available. If you want to upgrade your cloud software, you cannot take everything down and do the upgrade. A PaaS will typically provide some kind of rolling upgrade capability, where you can install a new version, test it while the old is still running, and once everything looks good, do a cutover to the new service instance. And then if things fail, you can roll back. 

In addition to these core five, the PaaS can provide other services:

1. Logging - log collection, storage, and analysis tools
2. Developer tools - integration with developer tools (e.g., Azure provides integration in Microsoft Developer Studio)
3. Monitoring services
4. Metrics and dashboards
5. Message bus services
6. And more.

All of this used to be the stuff that made writing server side software hard. With PaaS, these hard problems are solved for you and you can focus your energy on the business logic of the app itself.

PaaS is the operating system of the cloud, and it is the future of how server side software will be built. The race is now on - who will be the leaders in providing PaaS services? Like operating systems, apps are "sticky" to their particular platform and require porting to go from platform to platform. As the set of APIs and services for PaaS's grow, the choice of PaaS becomes more crucial as the costs of porting go up. This is one of the benefits of open source PaaS offerings like Cloud Foundry - instead of being wed to the APIs of a particular vendor, the APIs are defined by a community and can be improved by contribution.

As a followup to my original post on airplane travel, enclosed are additional rules and guidelines for making travel better for all. 

Getting In

1. When you arrive at your designated row, and there are people in the row already, politely ask them to get up so you can get into your seat.
2. Ask folks to get up only after your bags have been stored in the overheads.
3. As someone in the row being asked to get up for someone to take their window seat, smile and get up and out of the row quickly. If you are the person getting up and are in the aisle row, when you go into the aisle, step back two steps so the person in the middle seat can get out and stand just in front of you with enough room for the person in the window seat to step in.
4. If, for whatever reason, the people in the row have elected not to get up (typically this can happen in economy plus or first class seats), be very very careful when getting into the row, that you do not step on toes. More importantly, if you have a laptop bag or purse with you - do NOT carry this in your hands as you move into the row! Instead, drop it into your empty seat, then move into your seat area, and then move your bags as needed (into your hands, then under the seat). This avoids the almost inevitable hitting-people-in-the-face-with-your-bags which will happen if you do not do this.
5. If you do make your way into a row while people are seated there already, it is recommended to enter facing forward (so your back is to the people sitting in the row). Hold onto the chairs in the row in front of you so you dont lose your balance and fall backwards into the lap of the people sitting in the row. 

Olfactory Considerations

1. Shower the day of your flight, no matter what. An airplane is a close quarters environment and even if you don't normally do this or dont normally care, please for everyone elses sake - do so. (credit: John Loughney)
2. Do not wear perfume or cologne on flights. It can trigger allergies or make other passengers uncomfortable.  (credit: Mary Barnes)
3. If you bring food onto the airplane to eat, do not bring something with a strong lingering odor. Even if it smells good, this can be distracting to other passengers who may well be hungry but dont want to buy the low quality and overpriced food on the plane. Worse, if its something with a smell that is something only some people like (e.g., ethnic food like Indian or Asian), eat it before you get on the plane. 

Colds and Coughs

Hopefully it really goes without saying but if you've got a serious communicable disease, for goodness sake stay at home. For folks with minor colds or coughs, it is usually just unavoidable that you're going to sometimes have to get on a plane, if you do, here are some rules:

1. Bring your own tissues, have them with you at all times.
2. When you cough, you cough into a tissue so as to minimize spread of germs.
3. If is recommended to frequently wipe your nose and for tissues that you are done with, put them in a plastic bag that is inside of your laptop bag or purse or whatever. Don't leave them on the tray, don't stuff them in the pocket of the chair, don't leave them in your lap.
4. When you sneeze, sneeze into a tissue and immediately discard.
5. Bring hand sanitizer with you and use it frequently, after every sneeze and every once in a while after wiping your nose. 

Food Service

1. If the flight attendant comes and looks for food or drink orders, and they are trying to get the attention of the person next to you that doesn't notice them, help out and tap them on the shoulder and point to the flight attendant. Of course, do not do that if they are sleeping. This often happens when they are listening to music or a movie or engrossed in work.
2. When the attendant comes back with drinks or food, help pass them down the row so the attendant does not need to lean over everyone. (credit: Chaim Hass)
3. When the attendant comes back to collect trash, please help and pass forward trash from folks towards the window, so they don't need to reach over you to do so.
4. When passing drinks down, pay careful attention to any laptops or electronics that are out. Do NOT put the drink the airspace above said electronic device! One bump and its toast!
5. During beverage or food service, it's a social faux pas to get up and go to the washroom or get up in general. (credit: Dave Ward)
6. The people serving have a hard enough time getting drinks and food to other customers that having people in the aisles is more than a mild inconvenience. If you have to go and the carts are out but nothing served more than 6 rows "before you," then politely ask your aisle neighbors to let you out (remembering they are fixated on getting their drinks, snacks and food). Use the washroom that doesn't require the servers to have to push their cart back and forth to let you back into your seat or shimmy past the cart. Don't even think of getting up if you have to have them disrupt their service to accommodate your poor lack of timing. (credit: Dave Ward).
7. Never ask your aisle mates to let you out if they have been served food except for an imminent attack food poisoning or potential of gastrointestinal thermonuclear explosion. Getting up with food on your tray is almost impossible - the balancing act required almost always results in a spill or other catastrophe. (credit: Dave Ward).
8. For multi-course meals (typically first class), do not get up and go to the washroom between courses. There is almost certainly folks in your row still eating, or trays out, or flight attendants trying to get to the next round of service. Just way until the end of the service. (credit: Dave Ward).

Misbehaving Children

1. If there is a child behind you that is being loud, kicking the seat, or disturbing you, set a mental timer for 5 minutes. If the behavior does not improve after five minutes, you have the option of turning around to the parents of the child and asking politely for them to stop. (credit: Mary Barnes). Always ask the parent and not the child.

Overhead Bin Space Management

1. Like it or not, the overhead space is allocated in time order of boarding.
2. Once a bin is totally full, close it. 
3. If you are looking for space, please don't walk up and down the aisle opening closed bins. If they are closed it is because it is full already.
4. You may move items already in the bin in order to make space for your own, within reason. That means, moving within the bin, changing orientation, or putting the other item ONTOP of your own (not under) as long as it is not being crammed in. You may ask for jackets to be removed and moved. If you want to make a non-trivial move, ask the people in the row if the item is theirs before the move (e.g., moving to a different adjacent bin).
5. When on a redeye, if you have a laptop bag and a rollerboard, you may put both in the overhead storage in order to allow yourself room to stretch in the room under the seat in front of you. You may do this ONLY if your rollerboard fits lengthwise and your laptop bag or purse fit into the overhead standing up, not lying down. And only for redeyes.
6. You can put your jacket in the overhead, but you must put it ontop of your bag, or jammed between it and another bag.

This post was originally shared on Facebook. Enclosed you will find a slightly revised and improved version.

After many years of frequent air travel, I've  built up my personal list of air travel etiquette. Additions and comments welcome!


Leaning Back

1. Before you lean back in your chair, please look behind you. If the person is sleeping, go ahead. If they are working with a laptop, or eating on the tray, do not lean back all the way. Go just half way or 1/3. When you lean back, it makes it impossible for the person behind you to have enough room to see their laptop screen at a usable viewing angle. 
2. If you do lean back - do it slowly! To get maximum viewing angle on my screen, I will typically put the top of my laptop screen flush against the seat in front of me, often nudged in just below the release lever for the tray. If the person in front of me leans back suddenly, this puts pressure on my laptop screen and may damage it. Lean back slowly so the person behind you has time to react!
3. Only lean back if you intend to sleep or there is no one behind you. Remember, when you lean back, you are taking space away from the person behind you. Don't take if you don't need.
4. If you do lean back, please do not constantly adjust yourself or your seat position. As you lean back or forward, the position of your seat shifts, and thus impacts the person behind you. The person behind you will suffer from bouncing and shifting of their tray, and variation in the amount of space they have available to them. Comfort for people behind you is obtained when the amount of space they have is maximized and the variation in that space is minmized. Please, sit still and keep a constant wait on the back of your seat to avoid thee shifts.
5. If there is a car seat in the seat behind you holding a kid - never lean back.
   

The Middle Seat

1. Whomever sits in the middle seat gets to put their arms on the armrests. The people in the aisle and window seats have their own bits of "extra space" - the person in the aisle seat can lean into the aisle a bit or put their elbows out; the person in the window seat can lean against the wall more. The person in the middle row is crunched and the only extra space they can get is the armrests. It belongs to them.
2. When the middle seat is unoccupied, the free space becomes a shared, reusable resource, and gets split 50/50 between the person in the aisle seat and the person in the window seat. Either person can put down the laptop tray in the middle and claim one half of the space of that tray, as well as one half of the space of the seat itself. I typically use my half of the tray for coffee and food, so my own tray table can be used for my laptop and mouse. The space underneath the middle seat is for one party or the other, on a first come, first served basis.
   

Moving Seats

1. If you see an empty seat and want to move into it, the following rules apply:

• The seat change should not decrease the comfort level for the people in the area you want to move into. So for example, if you are currently in a middle seat, and want to move into a middle seat in a different row, but the aisle and window seats in your target row are taken, your move will decrease the comfort level for the people in the row you want to move to (and increase it in the row you are moving from). Consequently you should not make this move, nor should you ask the people in the target row if it is OK. Just stay where you are. Following similar logic, you can move into a target seat under the following cases: (1) The target row has no one seated in it, in which case you may take any seat. (2) The target row has someone in the aisle, and no one in the window or middle. You may take the window seat. (3) The target row has someone in the window seat, and no one in the aisle or middle. You may take the aisle seat.
• You make the move just after the door on the plane closes, and before takeoff. Don't defer your move until halfway through the flight, because moving in general annoys people as they get settled in. You'll have to go fast because the flight attendants don't generally like people moving around.
• Don't move your bags from the overhead, just take the stuff you had with you. Again, this is to avoid hustle and bustle and last minute shuffling of stuff.

The Window Shade

1. For morning and day flights, the window shade should stay down. This is to make sure the outside sun doesn't come in and cause glare on laptop screens and monitors. It is the job of the person in the window seat to close this shade. 
2. The person in the window shade may keep it open during landing and takeoff to observe the procedure. If it was closed initially, please check to make sure no one is sleeping next to you before  you open it. If you are in a mostly dark airplane interior (because everyone elses shade is closed), opening it can let in a glare of light that can awaken the people in your row.
   

Getting Out

1. If you need to get out of your seat to go to the restroom, and you are in a middle or window seat, you should turn to the other people and politely say, "Excuse me I need to get out". Before you do this, you should have packed up enough of your stuff that you can move once the other folks are ready. For example, if you had your laptop open on your tray, close the laptop, put it away, and close your tray table before asking.
2. The other people in the row should get out of their seats (exception in first class where there is enough room to exit without them getting up) to let the person out.
3. If you need to get out and one of the people in the row is sleeping, try and "schedule" this event. Don't wait till you urgently need to use the restroom. Keep an eye on the person who is sleeping, and if it looks like they wake, then go ahead. Give yourself about half an hour for this. If they do not wake, you gently tap them on the shoulder, and say, "Excuse me, I hate to wake you, but I need to get out". 
4. The exit process is the following. Person in the aisle exits first (naturally), and steps towards the front of the plane two steps, so that the middle person can get out and also step forward (typically restrooms are in the rear of the plane). Middle person comes next, goes into the aisle, steps forward towards the front of the plane. Now the window person can get out and use the restroom.
5. For people that have stepped out, there are two possible next-steps while they wait for the return. They can go back to their seats, remain in the aisle for a standing break, or take this opportunity to also go to the restroom. The person in the middle seat makes this call. If they remain standing, the person in the aisle seat should also remain standing and not complain. If the person in the middle seat returns to their seat, the person in the aisle seat can make an independent choice on whether to return to their seat or wait in the aisle or go to the restroom. Once the person who went to the restroom in the innermost seat comes back, the exit and return process repeats.
6. When you get out to let someone else go to the restroom, clear any blockages you left on the floor (e.g., your shoes or a bag) so that the person get out without needing to step over your stuff.
7. When getting out, it is frequently necessary to hold on to something to balance. You have two options - the seats in front of you, or the armrests of the seats in your row (the latter requiring you to turn around when exiting). The latter is recommended - it avoids pulling on the seats in front of you, which will bounce the people in front of you and decrease their comfort. If you turn around and lean forward slightly using the armrests to balance, you avoid touching the backs of the chairs in front of you which is nicer. 
8. When walking through the aisle, do NOT put your hands on the aisle seats as if you were mountain climbing up the aisle. Do not bump the seats with your shoulders or arms. The best way to move is to basically walk sideways. Move carefully so you are not moving those seats. Jostling them can wake sleeping passengers and in general decrease their comfort.
   

Turbulence

1. When there is turbulence, you are responsible for making sure your drink doesn't spill. You should either pick up your drink and hold it carefully to compensate for the turbulence, or put your hand over the top to prevent spill. If the drink is mostly empty and you are confident there will be no spills - you can leave it be but be careful it doesn't slide away.
   

The Bathroom

1. Be quick, even if no one was waiting behind you. Don't bring reading materials.
2. Throw away your paper towels.
3. You should use a seat protector. If you do, make sure it is completely flushed and some shreds of it haven't ripped off and landed on the floor. 
4. When using the sink, don't get water on the floor. Be careful to keep it in the sink.
5. Flush (really hope this is obvious).
6. Dont bother wiping down the sink. I know the instructions say to do this, but I feel its a waste of water and as long as the sink is just wet (as opposed to having soap on the sides of the sink), who cares. Sinks are wet normally.
7. Aim for guys really, really matters. If you miss and - ahem - get some on the toilet or floor, please wet a paper towel and wipe it up, then dry the floor and toilet area with a dry paper towel. The restroom is not cleaned during the flight. Its really gross to go to the bathroom and the floor is wet, and of course you dont know whether its water or not. If you enter the bathroom with a dry, clean floor, exit it with the same! Remember people on planes often remove their shoes and definitely no one wants to go into a bathroom with a wet floor wearing socks.
   

Armrest Movement

1. The default position of the armrests is lowered. If you want them raised, you must ask the person next to you if it is OK. If they say yes, then proceed. 
   

Lights and Air

1. You have complete autonomy over the controls for your light and your air vent. However, you may not adjust the direction of the airflow in a way that blows on the people next to you. 
2. You do not have the right to tell the people in your row to turn on or off their air, or turn on or off their overhead lights.
   

Getting on the Plane

1. Seriously - once you've found your row, if the aisle is unoccupied,  move yourself into that row and pull your bags with you, so that people can pass. The stuff that is meant to go under your seat, put that on the aisle row seat. Then, put your overhead stuff up top, all while mostly standing in front of the aisle row seat. This rule applies even if you need to put your bags into an overhead bin that is NOT your row. Move into the aisle seat area, put your bags up, then move on. 
2. Respect families and kids. As a frequent business traveler you get into this rush-rush mentality and will want to go first and lose patience with folks moving slowly. Let families with kids go first and give them time to do what they need to do. 
3. If you are in the window or middle seat, and arrive to your seat before there are folks there yet, go ahead and sit of course - but don't buckle your belt, don't lean back, don't open your tray table. Be in a position to move immediately to get out so the other person can get in.
   

Working

1. Never wedge your laptop screen into the seat in front of you, because the person in front of you probably hasn't read this. (credit: Scott Brim)