TCP/IP is actually a suite, or stack, of protocols that
interconnect and work together to provide for reliable and efficient
data communications across an internetwork. The major protocols of the
TCP/IP suite are:
Transmission Control Protocol (TCP)
How the TCP/IP Protocol Stack Maps to the OSI Model
* These are networking technologies that function at the Data Link and Physical layers.
They aren't TCP/IP protocols or a part of the TCP/IP protocol stack.
Application Layer Protocols
FTP
FTP is a reliable, connection-oriented tool used to copy files from one computer to another over a TCP/IP network, such as the Internet of an intranet.
Another flavor of FTP is Trivial File Transfer Protocol (TFTP), which is an unreliable (maining delivery is not guaranteed) file trasfer protocol. Cisco reouters use TFTP to store and retrieve configuration files from a TFTP server.
Telnet
Telnet is a terminal emulation protocol used on TCP/IP-based networks to remotely log into a remote device to run a program or manipulate data. Telnet was originally developed for ARPAnet and is an inherent part of the TCP/IP communications protocol. In the Cisco world, Telnet is used to access and configure routers from remote locations.
Transport Layer Protocols
Network protocols are either connection-oriented or connectionless.
Connection-Oriented and Connectionless Protocols
Establishing a connection-oriented connection involves the process
of setting up sequence and acknowledgment fields and agreeing upon the
port numbers to be used. This is accomplished by a three-step handshake
process that works like this:
At this point, the connection is successfully established and the applications can begin transferring data. Both TCP and UDP use port number to move information along to the application layer.
The registering body, IANA (Internet Assigned Numbers Authority), divides port numbers into three groups:
Additional informaiton to know about port numbers:
Well-Known Ports
Transmission Control Protocol (TCP)
TCP is a connection-oriented reliable, delivery protocol that ensures that packets arrive at their destination error-free. Using TCP is similar to sending a registered letter. When you send the letter, you know for sure that it will get to its destination and that you'll be notivied that it got there in good condition.
What to know about TCP:
On the Transport layer, packets are referred to as segments. The image below depicts the format of the TCP segment:
TCP Segment Description
User Datagram Protocol (UDP)
Remember that UDP is connectionless and unreliable. UDP Datagram
UDP Datagram Description
Network Layer Protocols
A number of TCP/IP protocols operate on the Network layer of the OSI Model, including IP, ARP, RARP, BOOTP, and ICMP. Remember, the OSI Network layer is concerned with routing messages across the internetwork.
Internet Protocol (IP)
Where TCP is connection-oriented, IP is connectionless. IP provides for the best-effort delivery of the packets (or datagrams) that it creates from the setments it receives from the Transport layer protocols. The IP protocol provides for logical addressing on the Network layer.
User Datagram Protocol (UDP)
Domain Name System (DNS)
Internet Protocol (IP)
Address Resolutions Protocol (ARP)
File Transport Protocol (FTP)
Simple Mail Transport Protocol (SMTP)
Post Office Protocol (POP3)
Interactive Mail Access Protocol (IMAP)
Internet Control Message Protocol (ICMP)
Routing Information Protocol (RIP)
Open Shortest Path First (OSPF)
Hypertext Transfer Protocol (HTTP)
TCP/IP Utilities (PING, Telnet, IPCONFIG, ARP, and more)
Connection-oriented protocols - require
that a direct connection be established between two devices before data
can begin to transfer between the devices. Packets are transferred
using a prescribed sequence of actions that include an acknowledgment to
signal when a packet arrives, and possibly resending the packet if
there are errors. This method is reliable and, as a result of its
reliability and the overhead involved, much slower than connectionless
protocols.
Connectionless protocols - are largely based on
your faith in the technology. Packets are sent over the network
without regard to whether they actually arrive at their destinations.
There are no acknowledgments or guarantees, but you can send a datagram
to many different destinations at the same time. Connectionless
protocols are fast because no time is used in establishing and tearing
down connections. Connectionless protocols are also referred to as best-effort protocols.
Handshake one: Host 1 sends a synchronization message to Host 2
Handshake two: Host 2 acknowledges Host 1's synchronization message and sends back its own synchronization message.
Handshake three: Host 1 acknowledges Host 2's synchronizattion message.
Well-known ports - are the most commonly used TCP/IP ports.
These ports are in the range of 0 through 1023. These ports can be
used only by system processes or privileged programs. Well-known ports
are TCP ports but are usually registered to UDP services as well.
Registered ports - are in the range of 1024 through 49151.
Registered ports are used on most systems by user programs to create and
control logical connections between proprietary programs.
Dynamic (private) ports - are in the range of 49152 through
65525. These ports are unregistered and can be used dynamically for
private connections.
Port numbers below 256 are assigned to public applications.
Port numbers 256 - 1023 are assigned to companies for saleable applications
Port numbers above 1023 are dynamically assigned in the host application
Source and destination port numbers don't have to be the same
Connection-oriented
Reliable transfer
Error-checking
Full-duplex transmission
Flow control
Multiplexing
| OSI Layers | TCP/IP Protocols |
| Application, Presentation, Session | Telnet, FTP, SMTP, SNMP, DNS, HTTP |
| Transport | TCP, UDP |
| Network | IP, ICMP, ARP, RARP |
| Data Link, Physical | Ethernet, Token Ring, FDDI* |
They aren't TCP/IP protocols or a part of the TCP/IP protocol stack.
FTP is a reliable, connection-oriented tool used to copy files from one computer to another over a TCP/IP network, such as the Internet of an intranet.
Another flavor of FTP is Trivial File Transfer Protocol (TFTP), which is an unreliable (maining delivery is not guaranteed) file trasfer protocol. Cisco reouters use TFTP to store and retrieve configuration files from a TFTP server.
Telnet
Telnet is a terminal emulation protocol used on TCP/IP-based networks to remotely log into a remote device to run a program or manipulate data. Telnet was originally developed for ARPAnet and is an inherent part of the TCP/IP communications protocol. In the Cisco world, Telnet is used to access and configure routers from remote locations.
Connection-Oriented and Connectionless Protocols
| Protocol | Type |
| FTP | Connection-oriented |
| IP | Connectionless |
| IPX | Connectionless |
| TCP | Connection-oriented |
| UDP | Connectionless |
| SPX | Connection-oriented |
At this point, the connection is successfully established and the applications can begin transferring data. Both TCP and UDP use port number to move information along to the application layer.
The registering body, IANA (Internet Assigned Numbers Authority), divides port numbers into three groups:
Additional informaiton to know about port numbers:
Well-Known Ports
| Port Number | Application |
| 21 | FTP |
| 23 | Telnet |
| 25 | SMTP |
| 69 | TFTP |
| 80 | HTTP |
TCP is a connection-oriented reliable, delivery protocol that ensures that packets arrive at their destination error-free. Using TCP is similar to sending a registered letter. When you send the letter, you know for sure that it will get to its destination and that you'll be notivied that it got there in good condition.
What to know about TCP:
On the Transport layer, packets are referred to as segments. The image below depicts the format of the TCP segment:
TCP Segment Description
| Field | Lenght in Bits | Purpose |
| Source port | 16 | The number of the calling port |
| Destination port | 16 | The number of the calling port |
| Sequence number | 32 | Used to ensure correct sequencing of data |
| Acknowledgment # | 32 | Sequence number of the next expected TCP octet |
| HLEN | 4 | Header lenght |
| Reserved | 6 | Set to zero |
| Code bits | 6 | Functions that set up and terminate the session |
| Window | 16 | Size of window sender can accept |
| Checksum | 16 | Sum of header and data fields (error correction feature) |
| Urgent Pointer | 16 | End of the urgent data |
| Option | 0 or 32 | Maximum TCP segment size |
| Data | - | Data from upper layers |
Remember that UDP is connectionless and unreliable. UDP Datagram
UDP Datagram Description
| Field | Size in Bits | Purpose |
| Source port | 16 | The number of the calling port |
| Destination port | 16 | The number of the called port |
| Length | 16 | The length of the datagram |
| Checksum | 16 | Sum of header and data fields (error correction feature) |
| Data | - | Data from upper layers |
A number of TCP/IP protocols operate on the Network layer of the OSI Model, including IP, ARP, RARP, BOOTP, and ICMP. Remember, the OSI Network layer is concerned with routing messages across the internetwork.
Internet Protocol (IP)
Where TCP is connection-oriented, IP is connectionless. IP provides for the best-effort delivery of the packets (or datagrams) that it creates from the setments it receives from the Transport layer protocols. The IP protocol provides for logical addressing on the Network layer.
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