URLs
http://www.ietf.org/ Navigate to the RFCs
http://www.princeton.edu/~psg/unix/Solaris/troubleshoot/index.html General Solaris troubleshooting
http://www.subnetmask.info/ Subnet calculator!
http://www.cut-the-knot.org/binary.shtml Base converter for decimal to binary and many others
1) Computers of different types should be able to communicate with each other over the network. A Mac needs to talk to a PC, which needs to talk to the IBM mainframe, which needs to talk to the DEC Alpha running VMS. They all need to talk to the computer that will be developed in 2 years and which will run a completely new OS.
2) The different parts of the same computer or network must communicate with the other parts in a format they can understand. The cabling has to transmit what the operating system puts out. The application has to put out information in a format that the OS can recognize. The parts of the network (hardware, OS, applications) are produced by different manufacturers; each manufacturer must know how to make components that will work with other manufacturers' components.
So what we need are 3 things:
A. An agreement on the breakdown of the network based on function.
B. Standards designed for individual functions.
C. The fewest rules possible so that the standards enhance innovation.
Design requirements for networking software and firmware are defined in a network model. A network model is a design for networking. It consists of published standards called "protocols", which are grouped into "layers" based on their function. A network model incorporates protocols of communications speed, software code, data format, sequencing, error handling etc. Everything involved in the network has protocols associated with it. The model is the sum total of all the standards for all the parts of the network. All software intended to work on a network of a particular model must adhere to the standards governing it. The standards are constantly being amended and new standards are frequently added. Any additions and changes to the model must be approved by an oversight agency.
Hardware standards are written by hardware manufacturers and are overseen and published by IEEE (Institute of Electrical and Electronic Engineers). They are not part of any network model, but all network models must work with available hardware.
Network models are broken up into "layers" which are defined sets of functions of the network and the protocols that govern those functions. For example, the "application layer" consists of standards for the functions typically performed by applications. The "network interface layer" mostly consists of standards governing the functions performed by NICs (network interface cards). Each layer has its own set of protocols, and when new protocols are written for the model, they will apply only to a particular layer.
The layers are organized into a "protocol stack," which is a sequence of networking functions. Software performing the functions of a particular layer communicates with layers above and below itself in the stack, accepting packets of information from the software implementing one layer, and passing packets to the software implementing the next layer in the stack .
A packet is any discrete, contiguous chunk of data passed over the network in a single stream.
The protocols applicable to a layer also govern communication with other layers in the protocol stack. That way, applications that will function on the network may be developed independent of operating systems and hardware. As long as they follow the standards applicable to their part of the network model, conformable applications will work.
The software or firmware of a particular layer also corresponds to the software or firmware of the same layer on another host and the packets produced by the software or firmware of each layer are read by the software or firmware of the corresponding layer on the other host. This principle is called peer-to-peer communication. The protocols allow communications between different systems, using different OS, as long as those systems follow the same network model.
There are two well-known network models, TCP/IP and ISO/OSI. The TCP/IP network model is governed by the IETF (Internet Engineering Task Force) and the ISO/OSI model is governed by ISO (International Organization for Standardization). The standard for the Internet is TCP/IP, and it is native to Unix, so TCP/IP is the model implemented by Solaris. The IETF oversees the publication of the TCP/IP standards, which are called "RFCs" (Requests For Comments). The name of the TCP/IP standards is meaningless; the IETF does not really want comments on published RFCs.
There are four layers in the TCP/IP network model. They are:
Application Layer
Transport Layer
Internet Layer
Network Interface Layer
Generally, in Solaris, the application layer is implemented by a Sun or 3rd party application. The network interface layer of the TCP/IP protocol stack is implemented in the PROM (Programmable Read-Only Memory) firmware or in firmware on a NIC (Network Interface Card). The other layers are implemented as kernel modules.
A packet of actual data generated by an application (the payload), sent over the network, passes from an application designed according to the protocols of the application layer to a kernel module that implements transport layer standards, to one or more kernel modules implementing the Internet layer, to the firmware of the PROM or NIC chip, which implements the network interface layer standards. The interface puts the packet out on to the wire that cables the host to the physical network.
During this process, each layer adds control information to the packet of data transmitted to it; usually headers, but sometimes also trailers. A header is packet metadata that precedes the actual packet payload over the wire; a trailer is packet metadata that follows the actual packet payload over the wire. This information allows the functions of the layer to be carried out. The process of adding information to the existing data packet is called "encapsulation". When a packet is received from another host, it passes from the hardware to the network interface, and thence through the Internet and transport layers to the application. At each layer, the header information is read and interpreted, and then the packet is passed to the next layer up in the protocol stack without the header, in the process of decapsulation.. Each layer removes the headers and trailers added by the corresponding layer on the originating host.
The Internet is an international set of networks, owned by Network Service Providers such as Sprint, Level 3, AT&T and many others, connected at NAPs, run by Network Service Providers, which follows the TCP/IP protocol. Its origins go back to the Eisenhower administration, and it was originally designed for defense purposes. The original network was called the Arpanet (after ARPA) and was sponsored by DARPA. The first Arpanet node was in UCLA. In 1988, the Arpanet was mostly removed from the U.S. Government and became the Internet.
Network Service Providers are wholesellers, and they resell network service to ISPs. ISPs are retailers of service to individuals and corporations.
The Internet is currently governed by ICANN, which has taken over the roles previously performed by IANA and the InterNIC.. ICANN distributes IP address and controls DNS domain names. In Europe, the Internet is overseen by RIPE, which stands for European IP Networks, and is located in Amsterdam.
Network Interface Layer
Parts: bridge, switch, ethernet port, computer
Specs: Ethernet (IEEE 802.3), Token bus, Token Ring standards, SLIP, PPP, ATM, FDDI.
Function: encapsulate/decapsulate data - puts on/ removes the source/destination hardware address (the MAC address). Puts on/ removes the size of the piece of information, and the type of information. Performs the most basic type of error checking - that the "frame" has been transmitted without error. Its job is to get data to the right node on the local link, whether that is a router or a non-router system.
Pieces of data: Frame
Address: MAC (Medium Access Control) address
Talks to: Hardware, Internet layer software
Internet Layer
Parts: routers
Specs: CNLS/CONS - connectionless-mode/connection-mode, ARP, RARP, IP, ICMP (ARP and RARP are really between the Data Link/Network Interface Layer and the Network/Internet Layer, rather than assigned to either one).
Function: Gets the data to the right network via routing, fragments and defragments data, performs network detection and error checking.
Pieces of data: Datagram
Address: IP address
Talks to: Transport layer software, Network Interface software
Transport Layer
Parts: programs such as NIS, mount, gateway
Specs: UDP,TCP (in TCP/IP)
Function: determines if data transmission is direction or non-directional, connection oriented or connectionless, stateful or stateless. It controls the quality of transmissions, keeping track of packet arrival, if that is required.. It gets data to the correct program.
Data produced: segment(TCP) datagram (UDP)
Address: Port number
Talks to: Applications, Internet layer software
Application Layer - transport
Parts: gateway
Specs: RPC, DNS, FTP, telnet, rlogin, DHCP, SMTP, SNMP, POP, IMAP, HTTP
Function: Connection, authentication, termination. The Session/Application layer allows a session to be established between hosts, including such things as authentication (verifying logins). The session layer determines which way data should be flowing at any time. In token rings, it determines what should be done with the token. In a gateway, the Session layer translates from one protocol to another and does filtering.
Application Layer - presentation
Specs: XDR
Function: Determines how the data is presented. It translates data into a format the application can use.
Application Layer - format
Specs: RPC, DNS, FTP, telnet, rlogin, DHCP, SMTP, SNMP, POP, IMAP, HTTP
Function: provides a user interface, and produces data to be transfered.
Pieces: stream/message
Talks to: transport layer software
ANSI - American National Standards Institute - standards organization - the umbrella
organization for IEEE and EI - responsible for defining standards for hardware and Ethernet.
ARP - Address Resolution Protocol - a protocol which maps the AP address to
a Mac address. This is an Internet Layer protocol in TCP/IP.
ARPA Advanced Projects Research Agency the originators of the internet, originally under contract with the Department of Defense.
ASCII - American Standard Code for Information Interchange - a data format.
ATM Asynchronous Transfer Mode - a type of backbone topology in which 53 byte cells are passed. It has a backbone of cables and switches and uses adaptor cards. It is used to create a virtual channel with guaranteed quality of service, generally for teleconferencing. It has a dedicated path and bandwith and a continuous connection.
BOOTP BOOTstrap Protocol a TCP/IP protocol of which DHCP is an enhancement. BOOTP provides the standards for the automatic download of IP adddresses to a client machine, but does not offer reusable IP addresses as DHCP does.
CCITT - Consultative Committee, International Telegraph and Telephone standards organization
CLNS/CONS - Connectionless mode/connection mode - a Network layer protocol in ISO/OSI.
CRC - Cyclical Redundancy Check - used to check the integrity of a packet using checksum.
CSMA/CD - Carrier Sense Multiple Access /Collision Detect - an ethernet standard in
which transmissions are broadcast over the entire network. The originating machine
listens for its own broadcast; if instead it hears a voltage spike, it assumes it collided with another
packet of information, and retransmits until it DOES hear it.
DARPA Defense Advanced Research Projects Agency sponsored the development of TCP/IP.
DHCP Dynamic Host Configuration Protocol a TCP/IP application layer protocol it allows the automatic assignment of IP address to a computer when it joins a network. It can reassign the address after the computer is shut down.
DLPI Data Link Provider Interface the protocol in Solaris which translates signals from various types of physical ports into a format understandable by the Network Interface Layer of TCP/IP. It is usually incorporated into streams drivers in the kernel.
DNS - a TCP/IP application layer protocol -
EBCDIC - Extended Binary Coded Decimal Interchange Code - a data format used by IBM mainframes.
EIA - Electronic Industries Association - standards organization
FDDI - Fiber Distributed Data Interface a standard for fiber optic cable, which is made of fibers of light-transmitting material such as glass or polymer.
FTP- a TCP/IP application layer protocol which transfers data.
HTTP - Hypertext Transfer Protocol - a TCP/IP application layer protocol for web browsers.
IAB - Internet Architecture Board - standards organization - the umbrella organization for IETF and IRTF.
IANA Internet Assigned Numbers Authority the organization which formerly controlled the assignment of IP addresses and well known port numbers. It also ran the Root Domain Name Service. These jobs are now done by ICANN.
IBM International Business machines Not Sun.
ICANN The Internet Corporation for Assigned Names and Numbers the international agency which controls DNS domain names, runs the Root Domain Name Service, and assigns IP addresses.
ICMP - Internet Control Message Protocol - protocol on the Internet layer of TCP/IP. It does error detection and error
IEC - International Electrotechnical Commission - standards organization
IEEE - Institute of Electrical and Electronic Engineers - standards organization
responsible for defining hardware protocols, such as 802.3 (all CSMA/CD Ethernet) and
802.3z (Gigabit ethernet), 802.11 (wireless) and 802.14 (cable modem).
IETF - Internet Engineering Task Force - standards organization - responsible for defining the protocols for TCP/IP in the form of RFCs.
IMAP-Internet Message Access Protocol - a TCP/IP Application Layer Protocol for mail
pickup from a remote server.
IP - internet protocol - a TCP/IP Internet Layer Protocol which determines the path to be taken by a packet, using its IP address.
IRTF - Internet Research Task Force - standards organization
ISO - International Organization for Standardization - standards organization the umbrella organization for ITU and ANSI. ISO developed the ISO/OSI model.
ISO/OSI - International Organization for Standardization/Open Systems Interconnection - a network model
ISOC Internet SOCiety a non-commercial, non-governmental organization of professionals that coordinates internet protocols. It is the umbrella organization for IANA.
ISP Internet Service Provider a reseller of internet access.
ITU - International Telecommunications Union - standards organization
LLC Logical Link Control a sublayer of the Data Link layer which translates for the network from the physical signal that comes over the wire.
MAC - Medium Access Control the hardware address of a network interface.
MDI - Medium Dependent Interface hardware type.
NSP Network Service Provider the owner of cabling and routers, which sells network access to the ISPs.
PDU - Packet Data Unit - a general term for a piece of data transmitted across a network. This term implies the use of the OSI seven layer model.
POP - Post Office Protocol - a TCP/IP Application layer protocol for mail pickup from a
central server.
PPP - Point to Point Protocol - a Network Interface Layer protocol which operates to send datagrams between point to point links such as phone lines.
RARP - Reverse Address Resolution Protocol - Maps a 48 bit Ethernet address to a 32 bit IP address. A RARP request from a diskless client uses the /etc/ethers file on the server to provide its IP address. This is a TCP/IP Internet Layer Protocol.
RFC - Request for Comments. Starting in 1969, documentation of the protocols for TCP/IP have been published in the form of a Request for Comments. There are now more than 3000 of these. The first was published as an ftp download at a site at UCLA. Individual authors may also publish RFCs. RFCs start out as Internet Drafts, which are posted (currently) on IETF's website (www.ietf.org) for commenting. They are then accepted or rejected for publication by the RFC editor. At that point the documents are posted on the IETF website as RFCs.
RIPE Riseaux IP Europeans the oversight organization of the internet in Europe.
RPC - Remote Procedure Call - protocol which allows programs in C to call on other machines to run procedures. RPC is used by NIS, and NFS.
SLIP - Serial Line Internet Protocol - a protocol used for modem to modem transmission across serial (telephone) lines at the Network Interface layer in TCP/IP. Superseded by PPP.
SMTP - Simple Mail Transfer Protocol - a TCP/IP Application Layer Protocol for email transmission. (sendmail).
SNMP - Simple Network Management Protocol - a TCP/IP Application Layer Protocol for monitoring network devices.
TCP - Transmission Control Protocol- a reliable, connection-oriented, stateful protocol at the Transport Layer of TCP/IP. It is full duplex, and controls connections between communicating hosts. It originates the opening and closing of connections to remote hosts, and acknowledges receipt of packets from originating hosts. It takes up more bandwidth than UDP, and is used when the originating host needs to know that packets have arrived at the destination.
TCP/IP - Transmission Control Protocol/Internet Protocol - a network model dominantly used in North America. Developed by the U.S. Department of Defense Advanced Projects Research Agency (DARPA). It is native to Unix.
UDP User Datagram Protocol. A TCP/IP Transport layer protocol which provides a half duplex delivery service between hosts. It is stateless, unreliable and connectionless. It is used when no acknowledgement of packets is needed, or when such acknowledgement is built into the application using UDP.
XDR - External Data Representation - a data descriptions language for the Presentation/Applications layer which translates machine dependent data to machine
independent data. Used by NFS and NIS.
Definitions
bridge a bridge connects 2 segments of cable, so all traffic goes through the bridge. The bridge reads the destination MAC addresses of packets and only passes through packets which have destinations on the other side of the bridge. Thus each section of cable does not see traffic that is both generated and received on the other side of the bridge. A bridge therefore reduces collisions by creating isolated collision domains.
circuit switching a type of network in which a dedicated circuit is formed between two computers, allowing a continuous stream of data to be transmitted. ATM networks are circuit switched. Circuit switched networks are ideal for video conferencing, since packets do not have to be reassembled into data streams at the receiving end. Telephone lines are circuit switched. Such networks require point to point connections between devices, and are said to be connection oriented.
encapsulation/decapsulation the process of adding/removing trailers from a packet of data, performed by the network layers.
gateway - a computer which translates from one protocol to another.
hub a multiport device which repeats data. By definition, a hub is half-duplex since data streams cannot be isolated to just one line in a hub it has no way to switch data streams between lines, and must resend all sent packets down all wires.
interface - an ethernet port, token ring port, AUI port, wireless network adapter, or serial line connection used for TCP/IP networking.
layer a set of standards applicable to one part of the network.
link local area / local link a network separated from other networks by a router. network model a concept of how a network is designed, incorporating protocols for various layers.
packet a generic term meaning a block of data with addressing information.
packet switching a type of network in which information is broken into packets, which are sent independent of other packets in the data stream and of other packets being transmitted over the network. No dedicated connection is set up between hosts, so packet switched networks are said to be connectionless. The Internet is a packet switched network.
peer-to-peer communication the concept that data produced by one host is read by the corresponding layer on the receiving host.
protocol a set of standards which may cover syntax (data format), semantics (error handling and control information) and timing of transmissions, depending on the type of protocol. The rules for communications and data transfer which govern protocol implementations.
protocol stack a set of cooperating software modules which pass data between themselves following specific rules of data formatting, packet size, packet types and message types.
repeater a 2 port device which receives data on one port and regenerates it out the other. Repeaters can be used to extend the allowable length of cable between a hub and a host.
router a host which forwards data from one network to another.
switch a multiport (>2) bridge it isolates traffic into collision domains by directing traffic to the correct subnet attached to it. Thus packets only travel the path from the originating subnet to the receiving subnet.