topic-system engineerring roles in software enginerring
cap 590
rollno.46
section-1101
reg no-11001009
submitted to-pawan sir
submitted by-jaspreet singh
TABLE OF CONTENTS
Introduction to tcp/ip
tcp
ip
operaction ,s of tcp/ip
layers in tcp/ip model
tcp/ip protocols
References
INTRODUCTION TCP/IP------------
The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite (IP), and is so common that the entire suite is often called TCP/IP. TCP provides reliable, ordered, error-checked delivery of a stream of octets between programs running on computers connected to a local area network, intranet or the public Internet. It resides at the transport layer.
Web browsers use TCP when they connect to servers on the World Wide Web, and it is used to deliver email and transfer files from one location to another. HTTP, HTTPS, SMTP, POP3, IMAP, SSH, FTP, Telnet and a variety of other protocols are typically encapsulated in TCP.
Applications that do not require the reliability of a TCP connection may instead use the connectionless User Datagram Protocol (UDP), which emphasizes low-overhead operation and reduced latency rather than error checking and delivery validation.
TCP----------
The Transmission Control Protocol (TCP) is one of the core protocols of the
Internet protocol suite. TCP provides reliable, in-order delivery of a stream of bytes, making it suitable for applications like file transfer and e-mail. It is so important in the Internet protocol suite that sometimes the entire suite is referred to as "the TCP/IP protocol suite." TCP is the transport protocol that manages the individual conversations between web servers and web clients.
Key Fields in the TCP Header
|Field |Function |
|Source Port |TCP port of sending host. |
|Destination Port |TCP port of destination host. |
|Sequence Number |Sequence number of the first byte of data in the TCP segment. |
|Acknowledgment Number |Sequence number of the byte the sender expects to receive next from the other side of the connection. |
|Window |Current size of a TCP buffer on the host sending this TCP segment to store incoming segments. |
|TCP Checksum |Verifies the integrity of the TCP header and the TCP data. |
1 IP---------------
IP is a connectionless, unreliable datagram protocol primarily responsible for addressing and routing packets between hosts. Connectionless means that a session is not established before exchanging data. Unreliable means that delivery is not guaranteed. IP will always make a best effort attempt to deliver a packet. An IP packet might be lost, delivered out of sequence, duplicated, or delayed. IP does not attempt to recover from these types of errors.
Key fields in the IP header
|IP Header Field |Function |
|Source IP Address |The IP address of the original source of the IP datagram. |
|Destination IP Address |The IP address of the final destination of the IP |
| |datagram. |
|Identification |Used to identify a specific IP datagram and to identify |
| |all fragments of a specific IP datagram if fragmentation |
| |occurs. |
|Protocol |Informs IP at the destination host whether to pass the |
| |packet up to TCP, UDP, ICMP, or other protocols. |
|Checksum |A simple mathematical computation used to verify the |
| |integrity of the IP header. |
|Time to Live (TTL) |Designates the number of networks on which the datagram is|
| |allowed to travel before being discarded by a router. The |
| |TTL is set by the sending host and is used to prevent |
| |packets from endlessly circulating on an IP internetwork. |
| |When forwarding an IP packet, routers are required to |
| |decrease the TTL by at least one. |
2.OPERATION OF TCP
Connection Establishment and Termination-----
TCP provides a connection-oriented service over packet switched networks.
Connection-oriented implies that there is a virtual connection between two endpoints. There are three phases in any virtual connection. These are the connection establishment, data transfer and connection termination phases. Three-Way Handshake----
In order for two hosts to communicate using TCP they must first establish a connection by exchanging messages in what is known as the three-way handshake. The diagram below depicts the process of the three-way handshake.
From figure 2.1, it can be seen that there are three TCP segments exchanged between two hosts, Host A and Host B. Reading down the diagram depicts events in time.
To start, Host A initiates the connection by sending a TCP segment with the
SYN control bit set and an initial sequence number (ISN) we represent as the variable x in the sequence number field.
At some moment later in time, Host B receives this SYN segment, processes it and responds with a TCP segment of its own. The response from Host B contains the SYN control bit set and its own ISN represented as variable y. Host
B also sets the ACK control bit to indicate the next expected byte from Host A should contain data starting with sequence number x+1.
When Host A receives Host B's ISN and ACK, it finishes the connection establishment phase by sending a final acknowledgement segment to Host B. In this case, Host A sets the ACK control bit and indicates the next expected byte from Host B by placing acknowledgement number y+1 in the acknowledgement field. In addition to the information shown in the diagram above, an exchange of source and destination ports to use for this connection are also included in each senders' segments.
The Network Interface Layer (also called the Network Access Layer) is responsible for placing TCP/IP packets on the network medium and receiving TCP/IP packets off the network medium. TCP/IP was designed to be independent of the network access method, frame format, and medium. In this way, TCP/IP can be used to connect differing network types. This includes LAN technologies such as Ethernet or Token Ring and WAN technologies such as X.25 or Frame Relay. Independence from any specific network technology gives TCP/IP the ability to be adapted to new technologies such as Asynchronous Transfer Mode (ATM).
The Network Interface Layer encompasses the Data Link and Physical layers of the OSI Model. Note that the Internet Layer does not take advantage of sequencing and acknowledgment services that may be present in the Data Link Layer. An unreliable Network Interface Layer is assumed, and reliable communications through session establishment and the sequencing and acknowledgment of packets is the responsibility of the Transport Layer.
3 Internet Layer
The Internet Layer is responsible for addressing, packaging, and routing functions. The core protocols of the Internet Layer are IP, ARP, ICMP, and IGMP.
The Internet Protocol (IP) is a routable protocol responsible for IP addressing and the fragmentation and reassembly of packets.
The Address Resolution Protocol (ARP) is responsible for the resolution of the Internet Layer address to the Network Interface Layer address, such as a hardware address.
The Internet Control Message Protocol (ICMP) is responsible for providing diagnostic functions and reporting errors or conditions regarding the delivery of IP packets.
The Internet Group Management Protocol (IGMP) is responsible for the management of IP multicast groups.
The Internet Layer is analogous to the Network layer of the OSI model.
4 Transport Layer
The Transport Layer (also known as the Host-to-Host Transport Layer) is responsible for providing the Application Layer with session and datagram communication services. The core protocols of the Transport Layer are TCP and the User Datagram Protocol (UDP).
TCP provides a one-to-one, connection-oriented, reliable communications service. TCP is responsible for the establishment of a TCP connection, the sequencing and acknowledgment of packets sent, and the recovery of packets lost during transmission.
UDP provides a one-to-one or one-to-many, connectionless, unreliable communications service. UDP is used when the amount of data to be transferred is small (such as the data that would fit into a single packet), when the overhead of establishing a TCP connection is not desired, or when the applications or upper layer protocols provide reliable delivery.
The Transport Layer encompasses the responsibilities of the OSI Transport Layer and some of the responsibilities of the OSI Session Layer.
5 Application Layer
The Application Layer provides applications the ability to access the services of the other layers and defines the protocols that applications use to exchange data. There are many Application Layer protocols and new protocols are always being developed.
The most widely known Application Layer protocols are those used for the exchange of user information:
The HyperText Transfer Protocol (HTTP) is used to transfer files that make up the Web pages of the World Wide Web.
The File Transfer Protocol (FTP) is used for interactive file transfer.
The Simple Mail Transfer Protocol (SMTP) is used for the transfer of mail messages and attachments.
Telnet, a terminal emulation protocol, is used for remote login to network hosts.
Additionally, the following Application Layer protocols help facilitate the use and management of TCP/IP networks:
The Domain Name System (DNS) is used to resolve a host name to an IP address.
The Routing Information Protocol (RIP) is a routing protocol that routers use to exchange routing information on an IP internetwork.
The Simple Network Management Protocol (SNMP) is used between network management console and network devices (routers, bridges, and intelligent hubs) to collect and exchange network management information.
2 TCP/IP Core Protocols
The TCP/IP protocol component that is installed in your network operating system is a series of interconnected protocols called the core protocols of TCP/IP. All other applications and other protocols in the TCP/IP protocol suite rely on the basic services provided by the following protocols: IP, ARP, ICMP, IGMP, TCP, and UDP.
The Internet layer is responsible for addressing, packaging, and routing functions. The core protocols of the Internet layer are IP, ARP, ICMP, and IGMP.
The Internet Protocol (IP) is a routable protocol responsible for IP addressing, routing, and the fragmentation and reassembly of packets.
The Address Resolution Protocol (ARP) is responsible for the resolution of the Internet layer address to the Network Interface layer address such as a hardware address.
The Internet Control Message Protocol (ICMP) is responsible for providing diagnostic functions and reporting errors due to the unsuccessful delivery of IP packets.
The Internet Group Management Protocol (IGMP) is responsible for the management of IP multicast groups.
The Internet layer is analogous to the Network layer of the OSI model.
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2 Transport Layer
The Transport layer (also known as the Host-to-Host Transport layer) is responsible for providing the Application layer with session and datagram communication services. The core protocols of the Transport layer are Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP).
TCP provides a one-to-one, connection-oriented, reliable communications service. TCP is responsible for the establishment of a TCP connection, the sequencing and acknowledgment of packets sent, and the recovery of packets lost during transmission.
UDP provides a one-to-one or one-to-many, connectionless, unreliable communications service. UDP is used when the amount of data to be transferred is small (such as the data that would fit into a single packet), when the overhead of establishing a TCP connection is not desired or when the applications or upper layer protocols provide reliable delivery.
The Transport layer encompasses the responsibilities of the OSI Transport layer and some of the responsibilities of the OSI Session layer.
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3 Application Layer
The Application layer provides applications the ability to access the services of the other layers and defines the protocols that applications use to exchange data. There are many Application layer protocols and new protocols are always being developed.
The most widely-known Application layer protocols are those used for the exchange of user information:
The Hypertext Transfer Protocol (HTTP) is used to transfer files that make up the Web pages of the World Wide Web.
The File Transfer Protocol (FTP) is used for interactive file transfer.
The Simple Mail Transfer Protocol (SMTP) is used for the transfer of mail messages and attachments.
Telnet, a terminal emulation protocol, is used for logging on remotely to network hosts.
Additionally, the following Application layer protocols help facilitate the use and management of TCP/IP networks:
The Domain Name System (DNS) is used to resolve a host name to an IP address.
The Routing Information Protocol (RIP) is a routing protocol that routers use to exchange routing information on an IP internetwork.
The Simple Network Management Protocol (SNMP) is used between a network management console and network devices (routers, bridges, intelligent hubs) to collect and exchange network management information.
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TCP over wireless--------
TCP has been optimized for wired networks. Any packet loss is considered to be the result of congestion and the congestion window size is reduced dramatically as a precaution. However, wireless links are known to experience sporadic and usually temporary losses due to fading, shadowing, hand off, and other radio effects, that cannot be considered congestion. After the (erroneous) back-off of
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the congestion window size, due to wireless packet loss, there can be a congestion avoidance phase with a conservative decrease in window size. This causes the radio link to be underutilized. Extensive research has been done on the subject of how to combat these harmful effects. Suggested solutions can be categorized as end-to-end solutions (which require modifications at the client and/or server), link layer solutions (such as RLP in CDMA 2000), or proxy based solutions (which require some changes in the network without modifying end nodes
References-----
internet working with tcp/ip by comber
An introduction to TCP/IP by John Davidson
Internet references---------- http://www.encyclopedia.com/doc/1G1-17568923.html http://condor.depaul.edu/~jkristof/technotes/tcp.html
http://www.erg.abdn.ac.uk/users/gorry/course/inet-pages/tcp.html
