Encapsulation question

tecnodog7

So many a times when we are doing frame relay, or switch port we use the encapsulation command.
My question is what does encapsulation mean. Like I read online but I am having a difficulty understanding.

This is from google. Can someone translate this for me please into understandable English.

Encapsulation is the packing of data and functions into a single component. The features of encapsulation are supported using classes in most object-oriented programming languages, although other alternatives also exist.

OfWolfAndMan

I want you to take a brief glance at this picture:

Encapsulation (networking) - Wikipedia, the free encyclopedia

Now I want you to think of an onion (Doesn't it make your eyes water just thinking about it? ). Now imagine for a moment that you can take this onion apart, layer per layer, and put it back together at will. At the core of this onion is application data (Whether it be FTP, HTTP, SMTP, whatever). Lets assume for a minute that Session, Presentation and Application Data is unified in this app data. Not much of an onion with any layers right?

Now your computer wants to send this application data to its destination, but how? HOW you ask? Well, before this packet can traverse the inter webs, it must have some layers attached to it, just like an onion! What's an onion without its layers? NOTHING! Nobody sheds a tear when an onion has no layers. Meaning a packet is nothing without the address data. What is the final destination? Oh that's cool, but I have to reach the first hop router first, how do I get there (Data Link)? How do I deal with packets that are out of order, and how do I know when to slow down if the other side can't handle all of my traffics (Transport)? After application data has been created, but before the information is physically sent over a link, the lower layer information is encapsulated, or wrapped around upper layer information. Transport header is wrapped around the application data, network data is wrapped around the trans header/app data, data link frame is wrapped around net data/trans header/app data, etc. Think of encapsulation as an envelope... inside an envelope... inside an envelope (I feel a movie title coming on. Inception of the Mail man!). When it gets to the right place, an envelope is taken off and replaced with another, or all the envelopes are removed altogether.

tecnodog7

Ohhhhhhhh ok makes sense now. So before the data can go anywhere everyone wants to give it it's own baggage. I'm still a bit fuzzy cuz there are so many encapsulation. For example in trunking we use 802.1q encapsulation. Verses when you are configuring frame relay it has it's own encapsulation frame relay or ppp. Does that mean it's applying it own envelopes? One sending with fedex while other with ups and other with usps?

But with that said I still get your analogy and it was beautiful.

Thank you

OfWolfAndMan

Thank you for that!

Now what does 802.1q and frame relay have in common? They're both data link layer protocols, along with ethernet, ARP, UDLD, STP, CDP, etc. When looking at the data link layer:

1. The message does not leave the intranetwork (Meaning anything before the first hop router)
2. They have different purposes in what kind of information they relay and what their ultimate objective is.

Think of each layer of the TCP/IP model as different categories of workers (IT, Sales, Administrative, Management, etc). Each has a different purpose, and all are necessary to make the system as a whole work. Now, think into subcategories (IT: Network, Systems, InfoSec, Project Manager, Software). These are the different protocols for each layer. Each has a different purpose, but they're not needed in every situation. Each has a specific objective. Some are needed in a workforce, others aren't needed at all. Their skill set could just not be relevant in the area, or obsolete altogether. A network guy can talk to a network guy, but a network guy is going to have difficulty explaining technical information to a Project Manager with minimal IT experience. At the same time, you're not going to send an SDN frame or a NDP frame into a Cisco Catalyst IOS environment. Why? They won't know what to do with the messages.

tecnodog7

Thank you. That has helped me understand the concept better than I originally stated.

tecnodog7

So i have read the post about 10 times and its finally starting to sink in. Once again OfWolfAndMan you are the man and thank you!

Vask3n

Great analogy Wolf, this is one example of those things where even if you may be familiar with the concept already, seeing it explained in a different way can both strengthen your current understanding and fill in any gaps you may have had.

OfWolfAndMan

Thanks guys! Glad to help.