TDP/IP includes a wide range of protocols which are used for a variety of purposes on the network. The set of protocols that
are a part of TCP/IP is called the TCP/IP protocol stack or the TCP/IP suite of protocols.
Considering the many protocols, message types, levels, and services that TCP/IP networking supports, I believe it would be
very helpful to categorize the various protocols that support TCP/IP networking and define their respective contribution to
the operation of networking. Unfortunately I have never seen this done to any real extent, but believe it would be worthwhile
to help those learning networking understand it faster and better. I cannot guarantee that experts will agree with the
categorizations that will be provided here, but they should help the reader get the big picture on the various protocols, and
thus clarify what the reason or need is for each protocol.
As mentioned previously, there are four TCP/IP layers. They are link, network, transport, and application. The link layer is
the hardware layer that provides ability to send messages between multiple locations. In the case of this document, ethernet
provides this capability. Below I define several categories some of which fit into the 4 layer protocol levels described
earlier. I also define a relative fundamental importance to the ability of the network to function at all. Importance includes
essential, critical, important, advanced, useful.
1. Essential - Without this all other categories are irrelevant.
2. Critical - The network, as designed, is useless without this ability.
3. Important - The network could function, but would be difficult to use and manage.
4. Advanced - Includes enhancements that make the network easier to use and manage.
5. Useful - Functionality that you would like to be able to use as a network user. Applications or some functionality is
supported here. Without this, why build a network?
The categories are:
Name(layer) Importance Names of protocols What it does
Hardware(link) Essential
ethernet, SLIP, PPP, Token Ring,
ARCnet
Allows messages to be packaged and sent
between physical locations.
Package management(network) Essential IP, ICMP
Manages movement of messages and
reports errors. It uses message protocols
and software to manage this process.
(includes routing)
Inter layer communication Essential ARP
Communicates between layers to allow one
layer to get information to support another
layer. This includes broadcasting
Service control(transport) Critical TCP, UDP
Controls the management of service
between computers. Based on values in
TCP and UDP messages a server knows
what service is being requested.
Application and user support Important DNS, RPC
DNS provides address to name translation
for locations and network cards. RPC
allows remote computer to perform
functions on other computers.
Network Management Advanced
RARP, BOOTP, DHCP, IGMP,
SNMP,RIP, OSPF, BGP, CIDR
Enhances network management and
increases functionality
Network Categories
Utility(Application) Useful
FTP, TFTP, SMTP, Telnet, NFS,
ping, Rlogin
Provides direct services to the user.
There are exceptions to my categorizations that don't fit into the normal layering scheme, such as IGMP is normally part of
the link layer, but I have tried to list these categorizations according to network functions and their relative importance to the
operation of the network. Also note that ethernet, which is not really a protocol, but an IEEE standard along with PPP, SLIP,
TokenRing, and ArcNet are not TCP/IP protocols but may support TCP/IP at the hardware or link layer, depending on the
network topology.
The list below gives a brief description of each protocol
l ethernet - Provides for transport of information between physical locations on ethernet cable. Data is passed in
ethernet packets
l SLIP - Serial line IP (SLIP), a form of data encapsulation for serial lines.
l PPP - Point to point protocol (PPP). A form of serial line data encapsulation that is an improvement over SLIP.
l IP - Internet Protocol (IP). Except for ARP and RARP all protocols' data packets will be packaged into an IP data
packet. Provides the mechanism to use software to address and manage data packets being sent to computers.
l ICMP - Internet control message protocol (ICMP) provides management and error reporting to help manage the
process of sending data between computers.
l ARP - Address resolution protocol (ARP) enables the packaging of IP data into ethernet packages. It is the system
and messaging protocol that is used to find the ethernet (hardware) address from a specific IP number. Without this
protocol, the ethernet package could not be generated from the IP package, because the ethernet address could not be
determined.
l TCP - A reliable connection oriented protocol used to control the management of application level services between
computers.
l UDP - An unreliable connection less protocol used to control the management of application level services between
computers.
l DNS - Domain Name Service, allows the network to determine IP addresses from names and vice versa.
l RARP - Reverse address resolution protocol (RARP) is used to allow a computer without a local permanent data
storage media to determine its IP address from its ethernet address.
l BOOTP - Bootstrap protocol is used to assign an IP address to diskless computers and tell it what server and file to
load which will provide it with an operating system.
l DHCP - Dynamic host configuration protocol (DHCP) is a method of assigning and controlling the IP addresses of
computers on a given network. It is a server based service that automatically assigns IP numbers when a computer
boots. This way the IP address of a computer does not need to be assigned manually. This makes changing networks
easier to manage. DHCP can perform all the functions of BOOTP.
l IGMP - Internet Group Management Protocol used to support multicasting.
l SNMP - Simple Network Management Protocol (SNMP). Used to manage all types of network elements based on
various data sent and received.
l RIP - Routing Information Protocol (RIP), used to dynamically update router tables on WANs or the internet.
l OSPF - Open Shortest Path First (OSPF) dynamic routing protocol.
l BGP - Border Gateway Protocol (BGP). A dynamic router protocol to communicate between routers on different
systems.
l CIDR - Classless Interdomain Routing (CIDR).
l FTP - File Transfer Protocol (FTP). Allows file transfer between two computers with login required.
l TFTP - Trivial File Transfer Protocol (TFTP). Allows file transfer between two computers with no login required. It
is limited, and is intended for diskless stations.
l SMTP - Simple Mail Transfer Protocol (SMTP).
l NFS - Network File System (NFS). A protocol that allows UNIX and Linux systems remotely mount each other's file
systems.
Network Categories
l Telnet - A method of opening a user session on a remote host.
l Ping - A program that uses ICMP to send diagnostic messages to other computers to tell if they are reachable over the
network.
l Rlogin - Remote login between UNIX hosts. This is outdated and is replaced by Telnet.
Each protocol ultimately has it's data packets wrapped in an ethernet, SLIP, or PPP packet (at the link level) in order to be
sent over the ethernet cable. Some protocol data packets are wrapped sequentially multiple times before being sent. For
example FTP data is wrapped in a TCP packet which is wrapped in a IP packet which is wrapped in a link packet (normally
ethernet). The diagram below shows the relationship between the protocols' sequential wrapping of data packets.
are a part of TCP/IP is called the TCP/IP protocol stack or the TCP/IP suite of protocols.
Considering the many protocols, message types, levels, and services that TCP/IP networking supports, I believe it would be
very helpful to categorize the various protocols that support TCP/IP networking and define their respective contribution to
the operation of networking. Unfortunately I have never seen this done to any real extent, but believe it would be worthwhile
to help those learning networking understand it faster and better. I cannot guarantee that experts will agree with the
categorizations that will be provided here, but they should help the reader get the big picture on the various protocols, and
thus clarify what the reason or need is for each protocol.
As mentioned previously, there are four TCP/IP layers. They are link, network, transport, and application. The link layer is
the hardware layer that provides ability to send messages between multiple locations. In the case of this document, ethernet
provides this capability. Below I define several categories some of which fit into the 4 layer protocol levels described
earlier. I also define a relative fundamental importance to the ability of the network to function at all. Importance includes
essential, critical, important, advanced, useful.
1. Essential - Without this all other categories are irrelevant.
2. Critical - The network, as designed, is useless without this ability.
3. Important - The network could function, but would be difficult to use and manage.
4. Advanced - Includes enhancements that make the network easier to use and manage.
5. Useful - Functionality that you would like to be able to use as a network user. Applications or some functionality is
supported here. Without this, why build a network?
The categories are:
Name(layer) Importance Names of protocols What it does
Hardware(link) Essential
ethernet, SLIP, PPP, Token Ring,
ARCnet
Allows messages to be packaged and sent
between physical locations.
Package management(network) Essential IP, ICMP
Manages movement of messages and
reports errors. It uses message protocols
and software to manage this process.
(includes routing)
Inter layer communication Essential ARP
Communicates between layers to allow one
layer to get information to support another
layer. This includes broadcasting
Service control(transport) Critical TCP, UDP
Controls the management of service
between computers. Based on values in
TCP and UDP messages a server knows
what service is being requested.
Application and user support Important DNS, RPC
DNS provides address to name translation
for locations and network cards. RPC
allows remote computer to perform
functions on other computers.
Network Management Advanced
RARP, BOOTP, DHCP, IGMP,
SNMP,RIP, OSPF, BGP, CIDR
Enhances network management and
increases functionality
Network Categories
Utility(Application) Useful
FTP, TFTP, SMTP, Telnet, NFS,
ping, Rlogin
Provides direct services to the user.
There are exceptions to my categorizations that don't fit into the normal layering scheme, such as IGMP is normally part of
the link layer, but I have tried to list these categorizations according to network functions and their relative importance to the
operation of the network. Also note that ethernet, which is not really a protocol, but an IEEE standard along with PPP, SLIP,
TokenRing, and ArcNet are not TCP/IP protocols but may support TCP/IP at the hardware or link layer, depending on the
network topology.
The list below gives a brief description of each protocol
l ethernet - Provides for transport of information between physical locations on ethernet cable. Data is passed in
ethernet packets
l SLIP - Serial line IP (SLIP), a form of data encapsulation for serial lines.
l PPP - Point to point protocol (PPP). A form of serial line data encapsulation that is an improvement over SLIP.
l IP - Internet Protocol (IP). Except for ARP and RARP all protocols' data packets will be packaged into an IP data
packet. Provides the mechanism to use software to address and manage data packets being sent to computers.
l ICMP - Internet control message protocol (ICMP) provides management and error reporting to help manage the
process of sending data between computers.
l ARP - Address resolution protocol (ARP) enables the packaging of IP data into ethernet packages. It is the system
and messaging protocol that is used to find the ethernet (hardware) address from a specific IP number. Without this
protocol, the ethernet package could not be generated from the IP package, because the ethernet address could not be
determined.
l TCP - A reliable connection oriented protocol used to control the management of application level services between
computers.
l UDP - An unreliable connection less protocol used to control the management of application level services between
computers.
l DNS - Domain Name Service, allows the network to determine IP addresses from names and vice versa.
l RARP - Reverse address resolution protocol (RARP) is used to allow a computer without a local permanent data
storage media to determine its IP address from its ethernet address.
l BOOTP - Bootstrap protocol is used to assign an IP address to diskless computers and tell it what server and file to
load which will provide it with an operating system.
l DHCP - Dynamic host configuration protocol (DHCP) is a method of assigning and controlling the IP addresses of
computers on a given network. It is a server based service that automatically assigns IP numbers when a computer
boots. This way the IP address of a computer does not need to be assigned manually. This makes changing networks
easier to manage. DHCP can perform all the functions of BOOTP.
l IGMP - Internet Group Management Protocol used to support multicasting.
l SNMP - Simple Network Management Protocol (SNMP). Used to manage all types of network elements based on
various data sent and received.
l RIP - Routing Information Protocol (RIP), used to dynamically update router tables on WANs or the internet.
l OSPF - Open Shortest Path First (OSPF) dynamic routing protocol.
l BGP - Border Gateway Protocol (BGP). A dynamic router protocol to communicate between routers on different
systems.
l CIDR - Classless Interdomain Routing (CIDR).
l FTP - File Transfer Protocol (FTP). Allows file transfer between two computers with login required.
l TFTP - Trivial File Transfer Protocol (TFTP). Allows file transfer between two computers with no login required. It
is limited, and is intended for diskless stations.
l SMTP - Simple Mail Transfer Protocol (SMTP).
l NFS - Network File System (NFS). A protocol that allows UNIX and Linux systems remotely mount each other's file
systems.
Network Categories
l Telnet - A method of opening a user session on a remote host.
l Ping - A program that uses ICMP to send diagnostic messages to other computers to tell if they are reachable over the
network.
l Rlogin - Remote login between UNIX hosts. This is outdated and is replaced by Telnet.
Each protocol ultimately has it's data packets wrapped in an ethernet, SLIP, or PPP packet (at the link level) in order to be
sent over the ethernet cable. Some protocol data packets are wrapped sequentially multiple times before being sent. For
example FTP data is wrapped in a TCP packet which is wrapped in a IP packet which is wrapped in a link packet (normally
ethernet). The diagram below shows the relationship between the protocols' sequential wrapping of data packets.
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