What are the characteristics of network applications? What are the different nature of (1) and stand-alone applications there? (2) What kind of network application architecture should adopt?
Architecture of network applications (1) The client / server architecture (Client-Server, C / S) (2) point to point configuration (the Peer-to-Use the peer, are P2P) (. 3) hybrid structure (the Hybrid)
The client / server architecture (1) Server | --7 * 24 hour service | - permanent access address / domain name | - the use of a large number of servers to achieve scalability (2) Client | - communicate with the server using services provided by the server | - intermittent access network | - may use dynamic IP addresses | - does not communicate directly with other clients (3) examples: Web
Pure P2P structure (1) is not an always-server (2) may be any direct communication between end-system / node (3) Intermittent access network node (4) may change the node IP address (5) advantages: highly scalable ( 6) disadvantages: difficult to manage
Hybrid structure (1) whether the two structures mixed together? (2) mixing the two at the same time be able to take advantage of it to avoid the disadvantages of both? (. 3) Napster | - P2P file transfer using the structure | - searching for a file using C / S Structure - Centralized | ---- register their content of each node to the central server | ---- each node submit a query request to the central server, look for interest
Questions (1) identify five or more for each network application architecture. (2) Comparison of the three architectures from advantages and disadvantages of various aspects / angles.
Interprocess communication network applications 2
Basic network applications: interprocess communication (1) Process: program running on the host. (2) How to communicate between processes running on the same host? | - inter-process communication mechanism | - operating system how to communicate between (3) processes running on different hosts? | - Message exchange (4) client process: initiating a process communication (5) server process: wait for the process communication request (6) Application using P2P architecture exists sub-process client / server processes it? Exist, when a host as a receiver, it will run the client process, and as the host of the sender on the running server process.
Socket: Socket between (1) the process using the communication socket send / receive messages implement (2) is similar to post the letter | - the sender mail message to the door | - dependent sender (outside) transmission infrastructure the news reached the facilities where the recipient host, and sent to the recipient's door | - recipient gets the message from the outside (3) transport infrastructure provides an API to process | - transport protocol selection | - parameters set up
How to address the process? (1) inter-process communication on different hosts, each process must have identifier (2) how to address a host? --IP address | --Q: After the host has an IP address, is sufficient to locate the process? | --A: No. At the same time on the same host may have multiple processes need to communicate. (3) port number / Number The Port - | assigned to each process needs to communicate with a host on port number |: - HTTP Server 80 | --Mail Server: 25 identifier (4) process | --IP + port number
Application layer protocol (1) network applications need to follow the application layer protocol (2) disclosed protocol | - RFC (Request For Comments) defined by | - allowing interoperability | - HTTP, the SMTP, ...... (. 3) proprietary protocol | - most P2P file-sharing applications
SUMMARY application layer protocol (1) message type (type) | - Request message | - Response Message Syntax (2) a message (synatx) / format | - which fields (field) with a message? | - describing how each field (3) field semantics (semantics) | - meaning of the information field (4) rule (the rules) | - process when sending / response messages | - the process of how to send / response news
3 network applications
Network applications demand for transport services (1) loss of data (data loss) / reliability (Reliability) | - Some network applications can tolerate some data loss: VoIP | - Some web applications require 100% reliable data transfer: file transfer, the Telnet (2) time (timing) / delay (delay) | - some applications only at sufficiently low latency when "effective" | - Internet phone / online games (3) Bandwidth (bandwidth) | - some applications only when the bandwidth of minimum requirements for "effective": network video | - some applications can adapt to any bandwidth - elastic application: email
Typical network applications demand for transport services
Transport service provided by the Internet (1) TCP service | - connection-oriented: between the client / server processes needed to establish a connection | - reliable transmission | - flow control: sender will not send too fast, the recipient of more than processing capacity | - congestion control: when the network load can limit the transmission rate of the sender | - does not provide a time / delay protection | - does not provide a minimum bandwidth guarantees (2) UDP service | - no connection | - - unreliable data transfer | - does not provide: reliability, security, flow control, congestion control, latency protection, bandwidth guarantees
Transport layer service in a typical network application
After-school practice (1) inventory of all your network application on your computer, make a list, including the name of network applications, functions, protocols and so on. (2) Based on the above list, create a table, analyzing these network applications demand for transport services. (3) analysis of these transport services network application using TCP or UDP.
