TCP/IP Architecture

It is an open protocol.

It allows public access to network protocols.

It allows integration between platforms over a network.

It is vendor independent.

The TCP/IP architecture is a different architecture than the OSI model. It comprises of four levels.

Application - Telnet, FTP, Gopher, SMTP, HTTP, MIME, POP, DNS, SNMP

Transport - TCP, UDP

Internet - IP, ARP

Network Interface - Ethernet, Token Ring, FDDI, X.25, ISDN, ATM, PPP, SLIP

 

Transport – TCP, UDP

(corresponds roughly to OSI Transport and Session Layer)

TCP is a sophisticated full-duplex (both directions of transmission are used simultaneously) protocol that chops the file to be transmitted into pieces called 'segments' that can be as small as 21 bytes and as big as 64,000 bytes. Each segment is sequenced by the sending TCP and acknowledged by the receiving TCP. The receiving TCP is controlling the flow of segments by allocating a 'window' of 'so many bytes' that the transmitter can send at any time. In addition, TCP can flag data as "urgent" or "externally urgent/to be pushed", and can negotiate maximum segment size. The segments are transmitted in sequence and checked for accuracy (with an error checking code called CRC or "Cyclic Redundancy Check") and retransmissions are requested when errors are detected.

TCP performs the packetizing

 

 

Internet – IP, ARP

(corresponds to OSI Network Layer)

IP makes the segments into datagrams by writing the IP headers, then sends the datagrams to a 'default router' (which the TCP/IP nerds call a gateway). Each router examines each datagram's IP header and compares the destination IP address to that of the network under its supervision. If the addresses match, than the router admits the packet in and sends it on the network to the destination host. If not, the router looks in some tables to find the next hop router (post office) where to send(route) the datagram. The last router (the one that matched the destination IP address to its network) has to physically deliver the datagram to the destination IP address host. Since there is absolutely no correspondence between an IP address and a MAC (Medium Access Control) physical address, the router has to have a table like a directory that shows which MAC address corresponds to which IP address. This table is called an Address Resolution Protocol (ARP) table. If the host's address is not in the table, the router will send an "ARP" packet asking "Host IP address - what's your MAC address, buddy?" The host responds (or some proxy for that host), and then the router sends the IP datagram to the physical MAC address found in the response.

 

IP Addressing

It encapsulates TCP packet in an IP datagram which contains a header with "lots" of information including Source Address and Destination Address (which are both 32 bits in length)

To accommodate different size networks, there are five classes of Internet addresses

Dynamic Addressing

Address Resolution
    1. Host sends an ARP request packet advertising the destination IP address asking for the associated data link layer address
    2. The destination machine will recognize it’s own IP address and send an ARP response along with its data link layer address

 

 

IP Routing

The process of determining the route or path through the network that a message will travel from the sending computer to the receiving computer

 

Network Interface

SLIP – Serial Link Internet Protocol

Provides asynchronous communication over duplex circuits. Usually used with dial-up connections.

PPP – Point to Point Protocol

Provides synchronous or asynchronous communication over duplex circuits. Can be used with dialed circuit, dedicated or circuit switched networks.

 

 

Application -

Telnet, FTP, Gopher, SMTP, HTTP, Finger, POP, DNS, SNMP

SMTP – Simple Mail Transfer Protocol

Other mail protocol standards

MIME – Multi-purpose Internet Mail Extension

 

 

 

 

HTTP – Hypertext Transfer Protocol

SNMP – Simple Network Management Protocol

McDaniel Notes