CHAPTER 6
DEFINING NETWORK PROTOCOLS
Lesson 1:
Introduction to Protocols ……… 234
Lesson 2: TCP/IP
………………………… 245
Lesson 3: NetWare
Protocols ……………. 252
Lesson 4: Other
Common Protocols……… 245
LESSON 1:
Introduction to Protocol
Protocols are the system of rules and procedures that govern communication between two or more
devices. Many varieties of protocols exist. Not all protocols are compatible, but as long as two devices
are using the same protocols, they can exchange data.
The Function of Protocols
Protocols are rules and procedures for communicating. The term “protocol” is used in a variety of
contexts. For example, diplomats from one country adhere to rules of protocol designed to help
them interact smoothly with diplomats from other countries. Rules of protocol apply in the same
way in the computer environment. When several computer are networked, the rules and technical
procedures governing their communication and interaction are called protocols. There are three
types of protocols:
a) While each protocol facilitates basic communications, each has different purposes
and accomplishes different tasks.
b) Some protocols work only at particular OSI Layers. The layer at which a
Protocol works describes its function. For example, a protocol that works
At a physical layer ensures that the data packet passes through the network
interface card (NIC) and out onto the network cable.
c) Protocols can also work together in a protocol stack. Different protocols also
work together at different levels in a single protocol stack. For example, the TCP/IP
protocol’s application layer maps to the OSI model’s presentation layer. Taken together,
the protocols describe the entire stack’s functions and capabilities.
How Protocols Work
The entire technical operation by which data is transmitted over the network has to be broken
down into discrete, systematic steps. Each step includes its own rules and procedures, or protocol.
========================================================================
netnotes6.html
PAGE 2 2001/10/02
The protocol steps must be carried out in a consistent order that is the same on every computer in the network.
In the sending
computer, these steps must be executed from the top down. In the receiving computer,
these steps must be carried out from the bottom up.
The Sending Computer
Protocols at the sending computer:
a) Break the data into smaller sections, called packets, that the protocol can handle.
b) Add addressing information to the packets so that the destination computer on the
Network can determine that the data belongs to it.
c) Prepare the data for transmission through the NIC and out onto the network cable.
The Receiving Computer
Protocols at the receiving computer carry out the same series of steps in reverse order. They:
a) Take the data packets off the cable.
b) Bring the data packets into the computer through the NIC.
c) Strip the data packets of all the transmitting information that was added by
the sending computer.
d) Copy the data from the packets to the buffer for reassembly.
e) Pass the reassembled data to the application in a usable form.
Both sending and receiving computer need to perform each step in the same way so that the data will have
the same structure when it is received as it did when it was sent.
Therefore, a computer using one of these protocols will not be able to communicate successfully with
a computer that is using the other protocol.
Routable Protocols
Data that is sent from one LAN to another along any of several available paths is said to be routed.
TCP/IP is routable, and you need to configure the address.
Net Beui is not routable, you just install and go, easy to set up. The only disadvantage of Net Beui
is it broadcasts everything, so there is a lot of chatter on the lines.
When you have a router you segment your Drive. If you have a Broadcast Storm, you can
potentially bring down your Network.
======================================================================
netnotes6.html PAGE 3
2001/10/02
Protocols in a Layered Architecture
In a network, several protocols have to work together. By working together, they ensure that the data is
properly prepared, transferred to
the right destination, received and acted upon. The
results of this
coordination efforts are known as layering.
Protocol Stacks
A protocol stack is a combination of protocols. Each layer of the stack specifies a different protocol
for handling a function or subsystem of the communication process. The protocols define the rules for
each layer in the OSI model.
7. APPLICATION |
6. PRESENTATION |
5. SESSION |
4. TRANSPORT |
3. NETWORK
|
2. DATA-LINK |
1. PHYSICAL |
Application – Initiates a request or accepts a request
Presentation – Adds formatting, display, and encryption information to the packet
Session – Adds traffic flow information to determine when the packet gets sent
Transport – Adds error-handling information
Network – Sequencing and address information is added to the packet
Data-Link—Adds error-checking information and prepares data for going on to the
Physical connection
Physical – Packet sent as a bit stream
=======================================================================
netnotes6.html PAGE 4
2001/10/02
Advantage of the Protocol Stack
TCP is one type of protocol. The protocol stack is segmented so if a protocol is not working as required,
or it needs to be changed, it can be removed. Don’t forget each layer only
communicates with the
one above and
below it. It uses an interface to do the
communicating.
The lower layers in the OSI model specify how manufacturers can make their equipment connect to the
equipment from other manufacturers, for example, by using NIC’s from several manufacturers on the same
LAN. As long as they operate with the same protocols, they are able to send and receive data from each
other. The upper layers specify rules for conducting communications sessions (the time during which two
computer maintain a connection) and the interpretation of applications. The higher they are in the stack,
the more sophisticated the tasks and their associated protocols become.
The Binding Process
The binding process is the process where protocols become connected to each other and the NIC.
Protocols and NIC’s can be mixed and matched. You can also have the ability to have several cards
attached to one NIC card. If there is more than one NIC in the computer, one protocol stack can
be bound to either or both NICs.
a) TCP/IP
b) NWLink
c) Net Beui
The NIC card looks at the protocol card that is the most frequently used. The binding order
determines the sequence in which the operating system runs the protocol. When multiple protocols
are bound to a single NIC, the binding order is the sequence in which the protocols will be utilized to
attempt a successful connection. If the TCP/IP is the first protocol to be bound, the network operating
system will attempt a network connection via TCP/IP before attempting to use another protocol. It is
kind of like the Default Protocol. If this network connection fails, it will go looking for the next in line.
The binding process consists of more than just binding the protocol stack to the NIC. Protocol stacks
need to be bound or associated with the components above and below them so that data can proceed
smoothly through the stack during execution. For example, TCP/IP may be bound to the Network Basic
I/O system (Net BIOS) session layer above as well as to the NIC driver below it. The NIC driver is
also bound to the NIC.
======================================================================
netnotes5.html PAGE 5
2001/10/02
Standard Stacks
Listed below are the most important protocol stacks:
a) The ISO/OSI protocol suite.
b) The IBM Systems Network Architecture (SNA)
c) Digital DECnet
d) Novell NetWare
e) Apple’s AppleTalk
f) The Internet protocol suite, TCP/IP
Protocols exist at each layer of these stacks, performing the tasks specified by that layer.
Application Protocols
Application protocols work at the uppermost layer of the OSI reference model.
Transport Protocols
Transport protocols facilitate communication sessions between computers and ensure that
data is able to move reliably between computers. Some examples are TCP/IP, NetBeui,
and SPX.
Network Protocols
Network Protocols provide what are called ink services. These protocols handle addressing and
routing information, error-checking and retransmission requests. Some examples are IP,
IPX, NWLink.
The IEEE protocols at the physical layer are:
802.3 (Ethernet) The CSMA/CD protocol regulates network traffic by allowing a
transmission only when the network is clear and no other computer is
transmitting.
802.4 (token passing) This is a bus layout that uses token-passing scheme.
Each computer receives all the data, but only the computers that are addressed
respond. A token that travels the network determines which computer is able
to broadcast.
=====================================================================
netnotes5.html
PAGE 6
2001/10/02
802.5 (Token Ring) This is a logical ring network that transmits at either 4mbps or
16 mbps. Although this is called a ring, it more resembles a start with each
computer branching off a hub. The ring is actually inside the hub.
A token traveling around the ring determines which computer can send data.
The IEEE has further defined the ISO layering protocols:
|
7. APPLICATION |
|
|
6. PRESENTATION |
|
|
5. SESSION |
|
|
4. TRANSPORT |
|
|
3. NETWORK |
|
|
2. DATA-LINK |
Media Access Control (MAC) |
|
1. PHYSICAL |
Logical Link Control (LLC) |
A MAC driver is
located at the Media Access control sublayer. This device driver is also
known as the NIC card.
A MAC protocol determines which computer can use the network cable when several computers
try to use it simultaneously. CSMA/CD, the 802.3 protocol allows computers to transmit data when
no other computer is transmitting. A collision may occur if two hosts transmit simultaneously. Then
they both wait and listen to the line, once it is clear they can retransmit.
Implementing and Removing Protocols
Essential protocols are installed automatically at the same time the initial operating system is installed
on the computer. To install protocols such as NWLink after the initial installation, the network
operating system usually includes a utility that leads the administrator through the process.
======================================================================
netnotes6.html
PAGE 7
2001/10/02
LESSON 2:
TCP/IP ******
IMPORTANT ******
Transmission Control Protocol/Internet Protocol, is an industry-standard suite of protocols that
provide communications in a heterogeneous (dissimilar elements) environment. TCP/IP
provides a routable, enterprise networking protocol and access to the Internet and its resources
TCP/IP is a robust protocol, and can reroute itself on the fly. TCP/IP was developed before
the ANSI and OSI standards were there.
TCP/IP has become the standard protocol used for interoperability among many different
types of computers. Most networks support TCP/IP as a protocol. Other protocols written
for TCP/IP are:
a) SMTP
(Simple Mail Transfer Protocol) E-Mail
b) FTP
(File Transfer Protocol) file exchanger among computers
c) SNMP (Simple Network Management Protocol) for networking environment
TCP/IP was developed in the
purpose was to maintain communication links between sites in the event of nuclear war.
not run independently, not by the
on the user’s behalf to install and configure. But, it has several advantages.
a)
Is an
industry standard This protocol
is not controlled by a single company.
It
is the de facto protocol of the Internet.
b)
Contains a set of utilities for connecting
dissimilar operating systems
c)
Uses scalable, cross-platform client-server
architecture TCP/IP can expand
(or shrink) to meet future
needs and circumstances. It uses sockets
to make the
computer operating systems
transparent to one another.
A socket is an identifier for a particular service on a particular node on a network.
TCP/IP has two disadvantages, its size and speed. TCP/IP is a relatively large protocol stack
that can cause problems in MS-DOS based clients.
TCP/IP STANDARDS
TCP/IP standards are published in RFC, or Requests for Comment. Internet development is
based on the concept of open standards. Anyone who wishes to participate in developing
standards for the Internet can. TCP/IP has an open set of standards, you can even set-up
another layer, as long as it can talk to the layer above and below it.
======================================================================
netnotes6.html PAGE 8
2001/10/02
TCP/IP and OSI
The TCP/IP protocol does not exactly match the OSI model. Instead of 7 layers it uses 4.
Commonly referred to the Internet Protocol Suite, TCP/IP is broken down into the following layers:
|
a) Application |
|
b) Transport |
|
c) Internet |
|
d) Network Interface Layer |
Each of these layers corresponds to one or more layers of the OSI model.
a)
Network Interface Layer
This layer corresponds to the physical and data-link layers of the OSI model, and communicates
directly with the network. It provides the interface between the network architecture (such as
a token ring, Ethernet) and the Internet layer.
b)
Internet Layer
This layer corresponds to the Network Layer of the OSI model, uses several protocol for routing
and delivering packets. There are several other protocols that function in this layer.
1) Internet Protocol (IP) This protocol performs addressing and route selection.
A packet is transmitted, and the header is attached much like a courier service would
attach a destination label on a package. IP does not want an acknowlegement when
the package arrives. Also, IP is responsible for assembly and disassembly of the
packet as set out by the rules for the physical and data-link layers of OSI.
Each IP packet is make up of a source and a destination address, protocol identifier,
checksum (a calculated value), and TTL (time to live).
The TTL tells each router on the network between the source and
the destination how long the packet has to remain on the network.
It works like a countdown counter or clock. As the packet passes through the router,
the router deducts the larger of one unit (on second) or the the time that the packet
was queued for delivery.
======================================================================
netnotes6.html PAGE
9
2001/10/02
For example, if a packet has a TTL of 128, it can stay on the network for 128
seconds or 182 hops (each stop or router along the way), or any combination of the two.
The purpose of the TTL is to prevent lost or damaged data packets (such as missing
E-Mail messages) from endlessly wandering the network. When the TL counts down
to zero, the packet is eliminated from the network.
Another method used by the IP to increase the speed of transmission is known as
ANDing. The purpose of ANDing is to determine whether the address is a local or a
remote site. If it is local the IP will ask the Address Resolution Protocol (ARP
for the hardware address of the destination machine. If the address is remote, the
IP checks its local routing table for a route of the destination. If the route exists, the
packet is sent on its way. If no route exists, the packet is sent to the local default
gateway and then on its way. The ANDing is like a Air-Traffic Controller.
NOTE: the AND is a logical operation that combines the values of two bits (0, 1)
for two Boolean values (false, true) that returns a value of 1(true) if both input
values are 1(true) and returns a 0(false) otherwise.
(T + F = 0) (False)
For example, 1 + 0 = 0 (False)
1 + 1 = 1 (True)
(T+T = 1) (True)
101101101
111101110
total 101101100
2) Address Resolution Protocol (ARP) The ARP determines hardware
address or MAC that corresponds to an IP address. If ARP does not
contain the address on its own cache, it broadcasts a request for the
address. All hosts on the network process the request and, it they
contain a map to the address, pass the address back to the requestor.
the packet is then sent on its way, and the new address is stored in
the routers cache (or table). The ARP is also a utility.
3) Reverse Address Resolution Protocol (RARP) server maintains a data base
of machine numbers in the form of an ARP table or (cache) which is
created by the system administrator. When the RARP server receives
a request for an IP number from a node on the network, it responds by
checking its routing tale for the machine number of the requesting
node and sending the appropriate IP number back to the requesting
node.
=======================================================================
netnotes6.html PAGE
10
2001/10/02
4) Internet Control Message Protocol (ICMP) The ICMP is used by IP and
higher-level protocols to send and receive status reports about informa-
tion being transmitted. The ICMP control the flow of data, speed, of data
between themselves. If the flow of data is too fast for the router,
it request that other routers slow down. The two basic categories of ICMP
messages are reporting errors and sending queries.
C) Transport Layer
The Transport layer performs end to end communication to both hosts. It acknowledgement
of receipt, flow control, and sequencing of packets. It also handles transmissions of packets.
The transmission layer can use either TCP or User Datagram Protocol (UDP) protocols
depending on the requirements of the transmission.
Transmission Control Protocol (TCP)
The TCP sends data from one node to another. It is a connection based protocol and
establishes a connection between two machines before any data is transferred. The TCP
uses a three-way handshake. TCP is connections oriented, it needs to have an answer on
the other end.
1) The requestor send a packet specifying the port number it plans to use and
its initial sequence number (ISN) to the server.
2) The server acknowledges with its ISN, which consists of the requestor’s ISN,
plus 1.
3) The requestor acknowledges the acknowledgement with the server’s ISN,
plus 1.
In order to maintain a reliable connection, each packet must contain:
1) A source and destination TCP port number.
2) A sequence number for messages that must be broken into smaller pieces.
3) A checksum to ensure that information is sent without and error
4) An acknowledgement number that tells the sending machine which
pieces of the message have arrived.
5) TCP sliding Windows
======================================================================
netnotes6.html PAGE 11 2001/10/02
|
COMPARING NETWARE AND OSI REFERENCE
MODELS |
||
|
APPLICATION |
|
(NCP) (SAP) (RIP) |
|
PRESENTATION |
|
Netware Service Routing |
|
SESSION |
|
Core Advertising Information |
|
TRANSPORT |
|
Protocol Protocol Protocol |
|
|
|
|
|
NETWORK |
|
IPX/SPX |
|
|
|
|
|
DATA-LINK |
|
Media-Access Protocols |
|
PHYSICAL |
|
(Token-Ring, Ethernet, ARCnet) |
Ports, Sockets and Sliding Windows
Protocol port numbers are used to reference the location of a particulars application or process
on each machine. A port and a node address together make up a socket. Applications and
services can configure up to 65,536 ports. TCP/IP applications and services typically use the
first 1023 ports. The Internet Assigned Numbers Authority (IANA) has assigned these as
standard, or default, ports.
Services and applications use sockets to establish connections with another host. If applications
need to guarantee the delivery of data, the socket chooses the connection-oriented services (TCP).
If the application does not need a guarantee on data delivery, the socket chooses the connectionless
service (UDP).
A sliding window is used by TCP for transferring data between hosts. A sliding window allows
the sending computer to transmit data in a stream without having to wait for each packet to be
acknowledged. This allows the receiving machine to receive packets out of order and reorganize them
while it wais for more packets. The sending window keeps track of data that has been sent, and if
an acknowledgement is not received within a given amount of time, the packets are re-sent.
======================================================================
netnotes6.html PAGE 12 2001/10/02
The sliding window accepts multiple frames, with a default of 4, this speeds up transmission.
But be careful not to speed it up to say 40, this will time out and hang up the system. This changing
of the window size can be assessed in the Registry Program.
User Datagram Protocol (UDP)
A connectionless protocol, the UDP is responsible for end-to-end transmission of data. UDP is
best used for small amounts of data. The UDP does not care if it receives and answer back. For
example, with video streaming you send a lot of information, say 30 frames/second to get live video.
Imagine 640X480 pixals of 30/frames/second traveling back and forth, and each time you send a
message back to say yes I’ve received the previous transmission. There would be lots of broadcast
storms as a result of it.
d) Application Layer
The Application layer connects applications to the network. Two application programming interfaces
are APIs and TCP/IP transport protocols and Windows Sockets and Net BIOS.
Windows Sockets Interface
A Socket is like a mail slot at the Post Office. You need to be able to dial out to access WinSock.
If you see internic.net, you will get a list of all ports, get a hard copy. WinSock is a networking API
designed to facilitate communications among different TCP/IP applications and protocol stacks.
WinSock provides a common interface for the applications and protocols that exist near the top
of the TCP/IP reference model. WinSock can communicate with and TCP/IP protocol and vise versa.
WinSock is derived from the original sockets that API created for the BDS Unix operation system.
FAT32 and Cluster Size:
A cluster is the smallest storage unit for a file on the drive. A drive can have multiple sectors.
A sector size is 512 bytes.
FAT32 can be a waste of space, because the cluster size is larger. Therefore, that means the
smallest unit of storage is assigned a larger area, therefore leaving lots of blank areas throughout the
disk, using up more storage. It is okay to set-up machines at home using FAT-32, it will be
more efficient. NOTE: NT cannot be FAT32 or in other words if NT you cannot have your primary
======================================================================
netnotes6.html PAGE 13 2001/10/02
drive C:> as FAT 32, but you can have secondary drives partitioned as FAT32. The setting are 10%
of Drive C (you can reduce this if you want. FAT is the File Allocation Table, and there
are always 2, one is a back-up. The back-up is held in the buffer.
Recycle is 10% of the drive, use it wisely, it has the deleted copies stored here, this could be useful,
if you decide you want to retrieve a accidentally deleted file. You can also cut back on the size of the
recycle bin %.
When is it best to uninstall a program?:
Right after the Boot-up of a machine, therefore the memory is clear, and there are no other programs
running.
LESSON 3:
NetWare Protocols
NetWare uses its own set of protocols, at how they relate to the OSI reference model.
Like TCP/IP, Novell provides a suite of protocols developed specifically for NetWare.
The five main protocols are:
Media Access Protocol
Internetwork packet exchange/Sequenced Packet Exchange(IPX/SPX)
Routing Information Protocols (RIP)
Service Advertising Protocol (SAP)
NetWare Core Protocol (NCP)
The above Novell protocols were finalized before the OSI Model, that is why they do not
match the OSI models. There is not direct link between the Novell layering and the OSI layering.
Media Access Protocols
This defines the addressing that distinguishes each node on a NetWare network. The addressing
is implemented on the NIC or the hardware. The most common are:
802.5 Token Ring
802.3 Ethernet
802.0 Ethernet
======================================================================
netnotes6.html PAGE 14 2001/10/02
This protocol is responsible for placing the header on the packet. Each header includes the source
and destination code. Once the packet is sent, each NIC checks the address, if their address
matches the NIC copies the packet and sends it up the protocol stack.
In addition the addressing, it adds the CRC, it ensure that the packet will be free of all errors.
The CRC error checking uses a complex calculation to generate a number based on the data
transmitted. Both the sending and receiving devices verify the check to ensure there are no
errors. If both devices get the same result it assumes the transmission was error-free. This is
known as the redundancy check.
The IEEE standard of 802.3 uses WIN95, WFW and NT 3.51
The IEEE standard of 802.2 uses WIN98, and NT4.
Internetwork Packet Exchange and
Sequenced Packet Exchange (IPX/SPX)
IPX/SPX randomly changes the numbers of the Network ID. Most administrators do not change it.
It is easy, you do not need individual IPX connectionless.
Internetwork addressing – The address of a segment on the network, identified by the network
number assigned during installation.
Intranode addressing – The address of a process within a node that is identified by a socket number.
Routing Information Protocol (RIP)
If the new RIP is static, you need to fill the routing table out manually, that means key it all in, and
that can take literally hours.
If the new RIP is dynamic, it broadcast to the other routers, hey guys heres my address, give me
yours. The New router dynamically builds up the table on its own.
The RIP is an extra field of data added to the packet to improve the decision criteria for selecting
the fastest route. Each time the RIP goes to the router it is called a Hop, and it can have a limit of
16 hops. Microsoft NT is the only Operating System that supports RIP. Several things occur
when a RIP is broadcast:
1) Workstations can locate the fastest route to a network number
2) Routers can request routing information from other routers to update their own
3) Internal tables. Routers respond to requests from workstations and other routers.
4) Routers can make sure all other routers are aware of the internetwork configuration.
5) Routers can detect a change in an internetwork configuration.
======================================================================
netnotes6.html PAGE 15 2001/10/02
Service Advertising Protocol (SAP)
The SAP allows service-providing nodes, file servers, print servers, gateways servers, and
application servers to advertise their services and addresses. SAP is very chatty.
By default the SAP server broadcasts its presence every 60 seconds. A SAP packet contains:
How to Know Protocols Work:
Each active protocol gives a port number from the IANA and ISA. The well known and well used
port numbers are 0-1023. FTP (21 send) and (22 receive)
http (default 80) and doom(666 port #)
NOTE: There are plenty of empty port numbers.
NetWare Core Protocol (NCP)
The NCP allows for clients and servers to interact. It provides transport and session services.
NCP cannot add and remove, it is just there. It does not fall into the OSI Model.
LESSON 4:
OTHER COMMON PROTOCOLS
Net BIOS
NetBios is how programmers get their information out of the network. It determines which protocol
it want to use, and chooses it on the fly. It will send it to a single or a group user. Most of the
services and applications that run within the Windows operating system use the NetBIOS Interface
or interprocess communication (IPC) NetBIOS interfaces exist for NetBEUI, NWLink, and
TCP/IP. NetBIOS
requires an IP address and a NetBIOS name to uniquely identify a computer.
NetBios is like the three-way handshake, doing many functions all at the same time.
======================================================================
netnotes6.html PAGE 16 2001/10/02
NetBIOS name resolution:
Each workstation on a network has one or more names. NetBIOS maintains a table of the
names and any aliases. The first name in the table is the unique name of the NIC. Optional user
names can be added to provide a user-friendly identification system. NetBIOS then cross-references
the name as required.
NetBIOS Datagram Service: This function allows a message to be sent to any name, group of
names, or to all users on the network. However, because this does not use point-to-point
connections, there is no guarantee that the message will arrive at its destination.
NetBIOS Session service: This service opens a point-to-point connection between two workstations
on the network. One workstation initiates a call to another and opens the connection. Because
both workstations are peers, they both can send and receive data concurrently.
NetBIOS NIC/session status: This function makes information about the local NIC, other NICs,
and any currently active sessions available to any application software using NetBIOS.
NetBeui
NetBeui is the acronym for NetBIOS (Extended User Interface). NetBeui and NetBIOS were
tightly connected as one product. But the manufacturers separated them.
NetBeui is a small, fast, and efficient transport-layer protocol that is supplied with all Microsoft
network products. Its advantage is it includes small stack size (especially for computers running
MS-DOS), its speed of data transfer on the network medium, and its compatibility with all
Microsoft-based networks.
Net Beui lives by broadcasts. NetBeui is small,
and fast. Some
disadvantages are it
is non-routable, and it is not Internet accessible.
Disadvantage of Netbeui is that it does not support routing. It is also limited to Microsoft based
networks. It is a good solution for a small peer-to-peer network where all workstations use
Microsoft Operation Systems.
======================================================================
netnotes6.html PAGE 17 2001/10/02
X.25 Packet Switching
When X.25 was developed it was most reliable, it would guarantee that it would arrive at the
destination. It was used in the 1960’s, and it was slow.
The X.25 protocol works in the physical, data-link layers of the OSI model.
NOTE: A flip-flop, is a circuit that alternates between two possible states when a pulse is
received at the input. For example, if the output of a flip-flop is high and pulse is received at
the input, the output “flips” to low, a second input pulse “flops” the output back to high, and so
on. It is a type of toggle switch.
The differences between X.25 and TCP/IP
node to node. With X.25, each node must respond to each router it comes
across, therefore making it very slow and sluggish. It is very slow, but
it is still out there. It has lost of overhead. It has something called
“store forward” it sends out a message before it sends the information, very
chatty.
mechanism.
over various types of media, with many different types of link service.
NOTE: Pad Pocket Assembler/disassembler, both ends must support X.25 or it will
not work. Cannot use a gateway to convert even.
XEROX Network Systems (XNS) (only know by name)
Was developed for Ethernet LAN’s. Was used a lot in the 1980’s but is being replaced
by TCP/IP. It is a large, slow protocol, but produces more broadcasts, causing more
network traffic.
======================================================================
netnotes6.html PAGE 18 2001/10/02
Advanced Program-to-Program Communication (APPC)
(Only know by name, not that important)
This is IBM’s transport protocol developed as part of its SNA. It was developed to
help application programs running on different computers to communicate and exchange
data directly. This is mainframe based, and is not that common.
AppleTalk (Know that
it exists)
MacIntoshes protocal enable computers to share files, and printers in a networked environment.
AppleTalk is also available on many UNIX systems.
AppleTalk Protocols
AppleTalk A collection of protocols that correspond to the OSI model.
It supports LocalTalk, EtherTalk, and TokenTalk.
LocalTalk Describes the simple, shielded, twisted-pair cable used to connect
Macintoshes to other Macintoshes or printers. A LocalTalk
Segment supports a maximum of 32 devices and operates at a
Speed of 230 Kbps.
EtherTalk AppleTalk over Ethernet. It operates at a speed of 10Mbps.
Fast EtherTalk operates at a speed of 100Mbps.
Token Talk AppleTalk over Token-Ring. Depending on its hardware, TokenTalk
Operates at either 4 Mbps or 16 Mbps.
OSI Protocol Suite
Each protocol maps directly to a single layer of the OSI model. The IEEE 802 series
Protocol, provide full networking functionality, including file access, printing, and terminal
emulation.
DECnet (don’t worry about
this one)
DECnet came after OSI layering was standardized. This protocol can overlap existing
NOS. DECnet defines communication network over Ethernet LAN’s, Fiber Distributed
Data Interface metropolitan area networks (FDDI MANs), and WANs that use private
or public data-transmission facilities. DECnet also uses TCP/IP and OSI protocols as
well as its own. It is a routable protocol.