Messages

In AH:

a) Transport Mode:
Entire packet Authenticated

b) Tunnel Mode:
Entire packet authenticated

https://imgur.com/a/yfnyRxn


In ESP:

1) Transport Mode:
Only ESPH-ESPT  authenticated
Original IP Header not authenticated.

2) Tunnel Mode:
Only ESPH-ESPT  authenticated
New IP Header not authenticated.

https://imgur.com/a/TawV5KA


Why is this difference found in them? Is there a reason behind them? Why not authenticate all of the packet? What problem would it create?

And why is there no such thing called AH auth but there's ESP Auth? Shouldn't AH Auth data also be in the figure shown above?

Also, Is there a reason why the modes are named "Tunnel" And "Transport"?

Source:https://networklessons.com/cisco/ccie-routing-switching/ipsec-internet-protocol-security

What's 2*80 in Hexa?

EDIT: shady looking link

The result is shown to be 1B. How did we get this value?

So, this looks like a case of carry in hexa addition, so how'd we do this calculation?


I'm asking this question because of this. Here' for j=8, Round Constant is 80. The formula to find next round constant is to multiply the current round constant with 2. So, it's 2*80 and should be 100. But it's not the case. So, I want to know how is it done?

Source: EDIT: shady looking link

Intranets Resource Assessments: Network Infrastructure, Clients andServer Resources

Protocols, Structure and Scope of Networks

The full chapter is this-:

Internet and Intranet Systems Development (6 hours)

Introductions

Benefits and drawbacks of intranets

Protocols, Structure and Scope of Networks

Intranets Resource Assessments: Network Infrastructure, Clients andServer Resources

Intranet Implementation Guidelines

Content Design, Development, Publishing and Management

Intranet Design with Open source Tools: DRUPAL, UMLA

Tunneling Protocols. VPN

I am asking coz these things are not included in our teacher's slides. If you are eager to see it, here are they-:

https://drive.google.com/file/d/1SH9buT91POy-MqvsYD4CT40Fgh8cHPTr/view

https://drive.google.com/file/d/1WO81kwHQy4E1gFQnvP12_pYcYgMCTYKt/view

I don't have any teachers atm and the I have exhausted all the resources that I have to figure what they might be saying. Ofc there is no such thing as someone accurately being able to tell "Yes this is this exactly 100%". But I want your educated guess on what could these topics (those 2 at the top) expecting students to learn? What are they about. I am the only one studying this course so I don't have any friends as well.

ah i see. things are more and more confusing. but how can 1 request give you multiple responses? what kind of request might that be?

This figure is the one given in not my textbook mentioned in syllabus but the local author book that many teachers use to follow while checking exam papers. If you don't write according to what is written in these books, they won't even give you 0.001 marks. So I want to learn this figure rather than others.

https://imgur.com/a/vBN9wtl

Here
-> first RTT for starting TCP connection,
-> second for requesting the base file with elements not loaded.


Why are multiple objects being received from just 1 request-response RTT? Should not just 1 object be received from it?
I am assuming that one RTT is to establish TCP connection yet again and another RTT is to request and get response. But why are there multiple objects being received in a single request response RTT, I don't get that and that's why the confusion for.
How does non persistent serial http connections work? (the slides that I've used are ambiguous so I am asking this question)

You can ignore the rest part of the question if you have answer to this already. It is all my unorganized thoughts about this topic, my hypothesis of how they should work etc.





My attempt at how non persistent parallel connections should work-:
I made this figure how I think non persistent parallel connection should be, can you verify it and if wrong help me make a new one?
https://imgur.com/a/hnsTz2R



Handmade figure is below which I hope is more clearer-:
https://imgur.com/a/6AFoCkV



explanations of this figure-:

1) initiate tcp connection for base file RTT happens

2) request-response RTT for base file happens

3) initiate tcp connection for element1 as soon as the base file RTT completes, then as soon as connection is set up, send request for element1-> then its response comes after some times.

4) initiate tcp connection for element2 as soon as tcp connection initiation for element1  starts , subsequently, send request for element2-> then its response comes.

5)then start closing tcp connections for base file, element1, then element2 consecutively.











HTTP Definitive guide figure discussion-:
What does connect-1 means in this figure below? Does it mean just starting the connection? Why is it not including the terminating of connection? Are we ignoring end of connection for each request-response in parallel connection?(If you watch the serial connection, it is ignoring tcp connection termination even in serial connections)
Source-: HTTP the definitive guide.
Both of the below figures I am assuming to be non persistent connections.
https://imgur.com/a/4QL4IZm














How non persistent(serial) connections should be working-:

But Isn't this how non persistent(serial) connections work?
-> tcp connection establishment 1 RTT
-> request response A 1 RTT
-> tcp connection close 1 RTT

Now for request response B
-> tcp connection establishment 1 RTT
-> request response B 1 RTT
-> tcp connection close 1 RTT

A source that confirms this-:
https://imgur.com/a/M1j3Ugs



But some sources are writing this-:

https://imgur.com/a/yZHjxpJ

So in this case there will be 1 less RTT for each file transfer i.e connection close RTT isn't considered. How is this alright? The first one that I said and this is totally different. As you can see for 2 objects, it will require just 2RTT+2 file transmission time

Now if i just calculate non persistent serial connection working(according to what I've understood from the slide just shown above)
-> 1 RTT to establish TCP connection
-> 1 RTT for request-response.
->file transfer time
-> 1 RTT for connection close
Again for second object same process happens. So it gives 6 RTTs+2*file transmission  time. Why isn't that the case in the slide shown there?The figures and explanations are from the same slides. (You can google kurose ross persistent non persistent http slides)

title-: What combination and permutation of version number should/can be used in request and response messages for persistent HTTP connections?

You can ignore rest of the post and just tell me the version number combinations that are allowed for persistent connections and little bit of why. I thought only 1.1 in request and 1.1 in response was allowed but I am seeing textbooks which are using combinations of 1.0 and 1.1, and 1.0 and 1.0 in request and response messages.


And for simplicity can I just used 1.1 both in request and response in these below figures instead for persistent connections?
​

Rest of the post-:

Image link-: https://i.stack.imgur.com/tsYd8.png


should not we use 1.1 there as that is the version of http for persistent connection? I don't understand this.

My confusion came due to this paragraph in the book.

Image link-:https://i.stack.imgur.com/85n34.png

HTTP 1.0 is non-persistent whereas HTTP 1.1 is persistent.

Here in figure 8-9 b), we are using persistent connection. But the version of HTP we are using is 1.0.


Remaining page just for context(same page as 1st red arrow confusion)-:

Image link-: https://i.stack.imgur.com/c8k1R.png

And for simplicity can I just used 1.1 both in request and response in these figures for persistent connections?




BELOW THIS ISN'T REQUIRED TO BE READ FOR ANSWERING THIS QUESTION


Not sure if they are related to my question, but I found them while googling about the issue.
According to RFC-:

"An HTTP client SHOULD send a request version equal to the highest
   version for which the client is at least conditionally compliant, and
   whose major version is no higher than the highest version supported
   by the server, if this is known.  An HTTP client MUST NOT send a
   version for which it is not at least conditionally compliant."

Not sure exactly what this would translate to.

https://stackoverflow.com/questions/57334986/why-is-http-version-number-presented-in-both-a-request-line-and-a-status-line

"An HTTP server SHOULD send a response version equal to the highest version for which the server is at least conditionally compliant, and whose major version is less than or equal to the one received in the request. An HTTP server MUST NOT send a version for which it is not at least conditionally compliant. A server MAY send a 505 (HTTP Version Not Supported) response if cannot send a response using the major version used in the client's request."

This means-:
if server supports 1.1, then for both 1.1 and 1.0 requests, it should respond with 1.1 response
if server supports only 1.0, then respond 1.1 request with 1.0 response

 I am not a web developer or anything professional. I am just a student learning topic called HTTP protocol. In which I got confused by PUT vs POST methods. This is probably not even 1 marks stuffs in most exams (unless we are explicitly asked about HTTP methods where it can weigh upto 2.5+2.5=5 marks as the maximum marks that can be asked from this topic is 10 marks and we would be expected to write 4 of the methods).

What's that all I need to know about this?
I did a huge research for learning this. Mostly I stumbled upon stackoverflow. Most online sites have copied pasted the stackoverflow answer. I haven't read the HTTP RFC as I feel

a) I am not at that caliber to read and understand RFC yet. I prefer reading books written by authors who simplify those RFCs.

b) I don't feel I should do this all for a subtopic(if my luck is bad, we could get asked HTTP methods for 10 marks in exam lol, hope i don't get jinxed).

But I have read MDN docs about them, but really speaking, they added no value to my learning. Maybe that is great for web developers but as a computer science student, that really didn't make lots of sense.

So till now I have collected this much information-:

1) PUT and POST both are same thing logically. It is just that one is used for sth and another for sth just for convention.

2)PUT write documents to server. It can create new documents in specified URL or if document already exists in that URL, it can replace its contents. Whereas POST is used to send input data to server rather than some random document data.





So the difference could be in type of data sent. One sends data to store in server only, whereas other sends data to query the server for other data.

3)PUT for update in CRUD, and POST for create in CRUD.

4) PUT-: I just want data to be created at this location. Or data to be updated if it already exists.
POST-: I just want data to be sent to this location.

5)PUT displays data to be sent in URL. POST doesn't. So PUT is used in google search, google maps, whereas POST is used in forms data.

6)PUT is idempotent meaning doing PUT 1000 times will have the same result as doing PUT 1 time.

This is all I have learnt. While I know whatever I have learnt is all correct and well. I want few things from the users of this website.
1) A simple definition that can explain PUT and POST.

If possible, extra explanations to solidify my concept.

Figure for explanations of PUT and POST-:

https://i.stack.imgur.com/nbHen.png

https://i.stack.imgur.com/iNS2T.png

can you guys explain how i can stuff bits in my case? and can you also explain about finding exact length of data from total length and padding?

Full question-: What should we do if the number of bytes to be transferred are not in multiples of eight in ipv4?

Theory that I want to understand is as follows-:
https://i.stack.imgur.com/RDVcG.png

So i found a question  that is relevant to this-:
->a total of 1440 bytes that is routed through an interface with MTU of 576 bytes. Calculate flag, fragmented offset, total length and data transmitted in each packet after fragmentation. Assume IP header to be 20 bytes.

Solution-:

1440=20+1420

MTU is 576.
Number of fragments=1420/576=3

So let's call 3 packets P1,P2,P3.

P1=>20+556
P2=>20+556
P3=>20+308

So I am trying to understand what the above picture is trying to say.

There are 2 cases-:
-> Is it trying to say that total length of P1 should be divisible by 8?

-> Is it trying to say that "only data" part should be divisible by 8?

I have even further questions about it.

->Say, the total length  of P1 should be divisible by 8. What will we do if it is not?

->(I believe) Say the "only data" part should be divisible by 8, then what should we do as neither 556 nor 308 is divided by 8.

So say I reiterate and do this arrangement(I  believe this is correct way)-:
P1->20+552
P2>20+552
P3->20+316

Still 316 isn't divisible by 8, what should I do now?

i don't understand the solution that is written in the picture that i attested above. how can we use that solution to our case?

IRRESPECTIVE OF WHATEVER I WROTE,if you want,YOU CAN EXPLAIN LIKE I AM BEGINNER TO ALL THESE

oh i see thanks for the kind information. i had no idea APNIC didn't support IPV4..

what are the cons and pros of doing it...this came in a subject we are studying this semester called internet and intranet...


i have asked this question because i learnt that isp could buy ip addresses directly from APNIC or from NIRs. what's the basic difference between buying from these two?


https://www.ioenotes.edu.np/ioe-syllabus/internet-and-intranet-1342

this is our syllabus if anyone is interested what's it all about.