Layer 4 of the TCP/IP protocol stack: Application level

Services: TELNET, FTP, SMTP, HTTP, DNS, RIP, NFSHierarchy of protocols and services

Contents

1. Overview of the TCP/IP Networking Model2. Comparison between OSI and TCP/IP

Networking Models3. Layer 4 (Application Layer) Overview4. TCP Services5. Conclusion6. Sources

Overview of the TCP/IP Networking Model

• Created in 1970s by DARPA• Describes the guidelines for creation of

specific protocols to enable communication over network

• Divided into layers

Comparison between OSI and TCP/IP Networking Models

• The OSI Model- Layer 1 – Physical- Layer 2 – Data Link- Layer 3 – Network- Layer 4 – Transport- Layer 5 – Session- Layer 6 – Presentation- Layer 7 – Application

Comparison between OSI and TCP/IP Networking Models

• The TCP/IP Model– Layer 1 – Link – Layer 2 – Network– Layer 3 – Transport– Layer 4 - Application

Comparison between OSI and TCP/IP Networking Models

Layer 4 (Application Layer) Overview

• Refers to the higher-level protocols used by most applications for network communication

• Application layer protocols are most often associated with client-server applications, and the commoner servers have specific ports assigned to them

TCP/IP Services• TELNET

- Primary goal - to allow a standard method of interfacing terminal devices and terminal-oriented processes to each other

TCP/IP Services

• FTP - Primary goal - to allow the exchange and manipulate files over a TCP/IP based network, such as the Internet

TCP/IP Services

• Types of FTP - From a networking perspective, the two main types of FTP: - active - passive

In active FTP, the FTP server initiates a data transfer connection back to the client. For passive FTP, the connection is initiated from the FTP client.

TCP/IP Services

TCP/IP Services

• SMTP - Primary goal – SMTP is a a text-based protocol, in which a mail sender communicates with a mail receiver over a reliable ordered data stream channel, typically a Transmission Control Protocol (TCP) connection

TCP/IP Services

TCP/IP Services

• HTTP- Primary Goal - HTTP is an application-level protocol for distributed, collaborative,

hypermedia information systems. Its use for retrieving inter-linked resources, called hypertext documents, led to the establishment of the World Wide Web

- Resources to be accessed by HTTP are identified using Uniform Resource Identifiers (URIs)—or, more specifically, Uniform Resource Locators (URLs)—using the http or https URI schemes.

TCP/IP Services

TCP/IP Services

• DNS- Primary Goal – The DNS is a hierarchical naming system for computers, services, or

any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participants.

TCP/IP Services

TCP/IP Services

• RIP - Primary Goal - (RIP) is a dynamic routing protocol used in local and wide area

networks. As such it is classified as an interior gateway protocol (IGP). It uses the distance-vector routing algorithm.

TCP/IP Services

• NFS- Primary Goal - Network File System (NFS) is a network file system protocol originally developed by Sun Microsystems in 1984, allowing a user on a client computer to access files over a network in a manner similar to how local storage is accessed.

ConclusionIn the last few years the IT has reached a new phase. Servers and home workstations

being able to transfer terabytes of data daily, multicore systems, multimedia systems are all around us. In this satiation to understand the basics of the TCP/IP Networking Model is a must for every system administrator nowadays. In this paper we have covered some of the main aspects of the model such as:

• Overview of the TCP/IP Networking Model• Comparison between OSI and TCP/IP Networking Models• Layer 4 (Application Layer) Overview• Various TCP Services (TELNET, FTP, SMTP, HTTP, DNS, RIP, NFS) as long as their

implementation and impact in our everyday live as users and as system administrators.

Sources

• http://en.wikipedia.org/wiki/Internet_Protocol_Suite• http://www.speedguide.net/read_articles.php?id=120• http://www.ietf.org/rfc/rfc854.txt• http://www.faqs.org/rfcs/rfc959.html• http://elqui.dcsc.utfsm.cl/util/redes/TCPIP%20Tutorial%20and%20Technical%20O

verview/3376c44.html• http://codeidol.com/unix/linux-fix/Linux-FTP-Server-Setup/FTP-Overview/• http://en.wikipedia.org/wiki/Simple_Mail_Transfer_Protocol• http://telecomm.boisestate.edu/itm305l.fall.2008/Lab13.htm• http://neranjara.org/article/title/SMTP_Protocol_Tutorial• http://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol• http://en.wikipedia.org/wiki/Domain_Name_System• https://www.dnsexit.com/support/knowledge_base/how_dns_works_files/dns-

basics.gif• http://en.wikipedia.org/wiki/Routing_Information_Protocol