Application Layer Flashcards
What are the characteristics of a client vs a server?
Dynamic vs permanent IP address, location, communication etc etc
What is a process?
A program running within a host
Client vs server process.
Process that initiates communication vs a process that waits to be contacted
How do processes communicate within the same host vs in different hosts?
Inter-process communication vs exchanging messages
What does a process use to send/receive messages?
A socket
What is the relationship between the host, processes, sockets, ip addresses and port numbers
Within a host, there are processes.
And processes send messages from client to server through sockets. Each host has an IP address, and each process within the host has a port number. This port number is an identifier, and each process must have on in order to receive messages
Does the IP address of the host on which a process runs suffice for identifying the process?
No, many processes can be running on the same host
What are the port numbers for the following servers?
Http (TCP)
Https (TCP)
Telnet (TCP)
DNS (UDP)
SSH (TCP)
mail server
Http (TCP) - 80
Https (TCP) - 443
Telnet (TCP) - 23
DNS (UDP) - 53
SSH (TCP) - 22
mail server - 25
What does an application layer protocol define?
Types of messages exchanged; message syntax; message semantics; rules for how processes send and respond to messages; open protocols, proprietary protocols.
What does reliable data transfer entail?
All bytes sent get to the other side in the same order with no gaps.
What transport service does an app need?
Data integrity which includes reliable data transfer; Timing, which refers to low delay, Throughput whether elastic or a minimum amount, And security, encryption and data integrity.
TCP vs UDP go.
Reliable transport, flow control, congestion control, connection oriented.
Vs
Unreliable data transfer.
What do neither TCP nor UDP have?
Timing, minimum throughput guarantee, and security.
How can TCP be made more secure?
Transport layer security (TLS) encrypts TCP connections and allow for data integrity and end point authentication.
What does a web page consist of?
Objects, a base html file which contains several referenced objects, each addressable by a URL.
What is a url comprised of?
A host name and a path name
In hypertext transfer protocol (HTTP), what is a client/server?
A client is a browser that requests receives and displays objects.
A server sends objects in response to requests.
What does it mean to say HTTP is stateless?
The server maintains no information about past client requests.
Non-persistent HTTP vs persistent HTTP.
For non persistent HTTP, only one object can be sent over TCP connection.
for persistent HTTP, multiple objects can be sent over one TCP connection.
What is round-trip time (RTT)?
The time for a small packet to travel from client to server and back.
Non-persistent HTTP response time =
2RTT + file transmission time
How does persistent HTTP address non persistent HTTP issues?
What are the two types of http messages?
Request and response
Name four http request methods
Get, post, head, put
List 5 http status response codes
200 OK
301 Moved Permanently
400 Bad Request
404 not found
505 http version not supported
Which http request-response interaction is stateless?
Get.
