Frame Relay - A packet-switching
protocol for
connecting devices on a Wide Area
Network (WAN). Frame Relay networks in the U.S. support data transfer rates
at T-1 (1.544 Mbps) and
T-3 (45 Mbps) speeds. In fact, you can think of Frame Relay as a way of
utilizing existing T-1
and T-3 lines
owned by a service provider. Most telephone companies now provide Frame Relay
service for customers who want connections at 56 Kbps to T-1 speeds. (In
Europe, Frame Relay speeds vary from 64 Kbps to 2 Mbps.
In the U.S., Frame Relay is quite popular because it is relatively inexpensive. However, it is being replaced in some areas by faster technologies, such as ATM
ATM - Asynchronous Transfer Mode, a network technology
based on transferring data in cells or packets of a
fixed size. The cell used with ATM is relatively small compared to units used
with older technologies. The small, constant cell size allows ATM equipment to
transmit video, audio,
and computer data over the same network, and assure that no single type of data
hogs the line.
Some people think that ATM holds
the answer to the Internet
bandwidth problem,
but others are skeptical. ATM creates a fixed channel, or route,
between two points whenever data transfer begins. This differs from TCP/IP, in which
messages are divided into packets
and each packet can take a different route from source to destination. This
difference makes it easier to track and bill data usage across an ATM network,
but it makes it less adaptable to sudden surges in network traffic.
When purchasing ATM service, you
generally have a choice of four different types of service:
· Constant Bit Rate (CBR) specifies a fixed bit rate so that data is sent in a steady stream. This is analogous to a leased line.
· Variable Bit Rate (VBR) provides a specified throughput capacity but data is not sent evenly. This is a popular choice for voice and videoconferencing data.
· Unspecified Bit Rate (UBR) does not guarantee any throughput levels. This is used for applications, such as file transfer, that can tolerate delays.
· Available Bit Rate (ABR) provides a guaranteed minimum capacity but allows data to be bursted at higher capacities when the network is free.
Packet-Switched - protocols in which
messages are divided into packets
before they are sent. Each packet is then transmitted individually and can even
follow different routes to its destination. Once all the packets forming a
message arrive at the destination, they are recompiled into the original
message.
Most modern Wide Area
Network (WAN) protocols, including TCP/IP, X.25, and Frame Relay, are
based on packet-switching technologies. In contrast, normal telephone service
is based on a circuit-switching
technology, in which a dedicated line is allocated for transmission between two
parties. Circuit-switching is ideal when data must be transmitted quickly and
must arrive in the same order in which it's sent. This is the case with most real-time data, such
as live audio and video.
Packet switching is more efficient and robust for data that can withstand some
delays in transmission, such as e-mail messages and Web pages.
A new technology, ATM, attempts to combine the best of both worlds -- the guaranteed delivery of circuit-switched networks and the robustness and efficiency of packet-switching networks.
Circuit-switched
- A type of communications
in which a dedicated
channel (or circuit)
is established for the duration of a transmission. The most ubiquitous
circuit-switching network is the telephone system, which links together wire
segments to create a single unbroken line for each telephone call.
The other common communications
method is packet
switching, which divides messages into packets and sends each packet
individually. The Internet
is based on a packet-switching protocol, TCP/IP.
Circuit-switching systems are
ideal for communications that require data to be transmitted in real-time.
Packet-switching networks are more efficient if some amount of delay is
acceptable.
Circuit-switching networks are sometimes called connection-oriented networks. Note, however, that although packet switching is essentially connectionless, a packet switching network can be made connection-oriented by using a higher-level protocol. TCP, for example, makes IP networks connection-oriented.
Cell-Switched
- The international
telephone community has committed to a future network design that combines
elements of both circuit and packet switching to enable the provision of
integrated services. The ITU (formerly CCITT, an international standards body
for telecommunications) has adopted a ``cell-switching'' technology called ATM
(asynchronous transfer mode) for future high-speed networks. Cell switching
closely resembles packet switching in that it breaks a data stream into packets
which are then placed on lines that are shared by several streams. One major
difference is that cells have a fixed size while packets can have different
sizes. This makes it possible in principle to offer bounded delay guarantees
(since a cell will not get stuck for a surprisingly long time behind an
unusually large packet).
An ATM network also resembles a
circuit-switched network in that it provides connection-oriented service. Each
connection has a set-up phase, during which a ``virtual circuit'' is created.
The fact that the circuit is virtual, not physical, provides two major
advantages. First, it is not necessary to reserve network resources for a given
connection; the economic efficiencies of statistical multiplexing can be
realized. Second, once a virtual circuit path is established switching time is
minimized, which allows much higher network throughput. Initial ATM networks
are already being operated at 155 Mbps, while the non-ATM Internet backbones
operate at no more than 45 Mbps. The path to 1000 Mbps (gigabit) networks seems
much clearer for ATM than for traditional packet switching. (ATM Cells are capable of 2.4 Gbps)
CISCO
NVRAM Non Volatile RAM Startup
Configuration For CISCO routers.. Boot strap program.
CISCO IOS Symbols
·
User mode -
o
Router>
·
Privileged mode
o
Router#
·
Help symbol
o
Router# command ?
Television
NTSC
525 Vertical Lines per Frame @ 30 Frames per Sec 60Hz
MPEG
Lossy compression - (as
used in JPEG) witch omits bits that the eye does not detect. An acceptable
Ratio is 24 to 1
Streaming 100mbs? Or 10mbps
MIDI Musical Instrument Digital Interface
Transmits sounds Over 16 channels that reproduce true instrument sounds, voice
sounds, and imitated and synthetic sounds.
PCM Pulse Code Modulation Converts an analog
audio signal to an 8-bit digital signal, and transmits the digital signal at 64Kbs.
2 PCM substandard exist, U-Law in US and A- Law in Europe . U-Law is used over
the internet and on intranets more than any other standard.
Latency
On WANs must be kept under 400 ms (Milliseconds)
·
Transmission Delay
Is the time it takes a packet to tralve across a network medium such as 10base-T cabling (Max speed 10 Mbps)or 100Base-TX cabling (Max Speed 100Mbps).
Besides the speed of the medium, transmission delay is influenced by the size
of the packet.
·
Propagation Delay
It is the time it takes for a packet to travel a segment or network, end to
end. Propagation delay is usually associated with fiber-optic media and the
speed of light through the media.
·
Processing delay
The time it takes for a bridge, switch, or router to compare frame or packet
contents with its table information, change the frame or packet header, and
provide any special services such as packet translation and reencapsulation, or
incrementing the hop count.
·
Switching delay or
Store-and-Forward Wich is the time used by a bridge, switch, or
router, to examine, process,. And retransmit a frame or packet.
Variable Latency Jitter (Min Lat = 200ms & Max =520ms, Jitter =
520ms-200ms=320ms
Unicast three separate transmission to reach
three transmissions to reach three separate workstations
Broadcast- One broadcast to all workstation
regardless of who wants to receive it.
Multicasting One transmission to the receiving
groups only.
Multipoint - ???
Streaming Data ,Audio, And Video
·
FDDI - Fiber Distributed Data Interface, a set of ANSI protocols for sending digital data over fiber optic cable.
FDDI networks are token-passing networks, and support data rates of up to
100 Mbps (100 million bits) per second. FDDI
networks are typically used as backbones for wide-area networks
·
DRI Dual Rings Interface (Like
Toke Ring)
·
RTP -
Real-Time Transport
Protocol, an Internet protocol for
transmitting real-time
data such as audio and video. RTP itself does not guarantee real-time delivery
of data, but it does provide mechanisms for the sending and receiving
applications to support streaming
data. Typically, RTP runs on top of the UDP protocol, although the
specification is general enough to support other transport protocols.
NOVELL
IPX
- Internetwork Packet
Exchange, a
networking protocol
used by the Novell
NetWare operating systems. Like UDP/IP, IPX is a datagram
protocol used for connectionless
communications. Higher-level protocols, such as SPX and NCP, are used for
additional error recovery services.
SPX - Sequenced Packet Exchange, a transport layer protocol (layer 4 of
the OSI Model) used in Novell Netware networks.
The SPX layer sits on top of the IPX layer (layer 3) and
provides connection-oriented services between two nodes on the network. SPX is
used primarily by client/server
applications. Whereas the IPX protocol is similar to IP, SPX is similar to TCP. Together, therefore,
IPX/SPX provides connection services similar to TCP/IP.
Protocol |
Full
Name |
Description |
OSI
Layer |
|
IPX |
Internet Pacet Exchange |
Used as the primary data transport protocol |
3 - 4 |
|
LSL |
Link Support Layer |
Used With ODI to enable multiprotocol support using one NIC |
2 |
|
MLID |
Multiple Link Interface Driver |
Connects tow or more channels into one link for telecommunications, for example for tow ISDN Tas. |
2 |
|
NCP |
NetWare Core Protocol |
Part of the shell software, enables client and server communications in order to access applications |
5-7 |
|
NLSP |
Netware Link Services Protocol |
Used For constructing packets with routing information |
3 |
|
RIP |
Router Information Protocol |
Gathers routing information for servers that are configured to provide routing services |
3 |
|
SAP |
Service Advertising Protocol |
Enables Netware Clients to identify servers and network service provided by each server |
3 |
|
SPX |
Sequenced Packets Exchange |
Provides connection-oriented data transport for applications |
4 |
TCP - Transmission Control Protocol, and pronounced as separate letters. TCP
is one of the main protocols
in TCP/IP networks.
Whereas the IP protocol
deals only with packets,
TCP enables two hosts
to establish a connection and exchange streams of data. TCP guarantees delivery
of data and also guarantees that packets will be delivered in the same order in
which they were sent.
MICROSOFT
NWLINK For NT to Novell, to allow connection to
novell servers and MS servers.
NetBEUI - NetBios Enhanced User Interface. It is an enhanced version of the NetBIOS protocol used by network operating systems such as LAN Manager, LAN Server, Windows for Workgroups, Windows 95 and Windows NT. Netbeui was originally designed by IBM for their Lan Manager server and later extended by Microsoft and Novell
NetBios - Network Basic
Input Output System, an application
programming interface (API)
that augments the DOS BIOS by adding special
functions for local-area
networks (LANs). Almost all LANs for PCs are based on the
NetBIOS. Some LAN manufacturers have even extended it, adding additional network capabilities.
NetBIOS relies on a message format called Server Message Block (SMB).
|
Name |
Full Name |
Description |
OSI Layer |
|
IP |
Internet Protocol |
Handles Addressing |
3 |
|
ICMP |
Internet Control Message Protocol |
Used for network error Reporting, particularly through routers. |
3 |
|
RIP |
Routing Information Protocol |
Used to gather routing infromati9on to update routing tables |
3 |
|
OSPF |
Open shortest Path First |
Used by routers to communicate routing information |
3 |
|
TCP |
Transport Control Protocol |
Ensures the Reliability of data transmission |
4 |
|
UDP |
User Datagram Protocol |
Used as an alternative to TCP |
4 |
|
ARP |
Address Resolution Protocol |
Enable resolution of dotted decimal addresses to computer names, and vice versa |
3 |
|
FTP |
File Transfer Protocol |
Used to transfer Files |
5-7 |
|
SLIP |
Serial Line Internet Protocol |
Used as a remote communications protocol in connection with WANs |
3 |
|
PPP |
Point to Point Protocol |
Used as a remote communications protocol in connection with WANs |
3 |
|
DNS |
Domain Name Service |
Maintains Tables to link dotted decimal addresses with computer names, and vice versa |
4 |
|
SMTP |
Simple Mail Transfer Protocol |
Used for E-Mail |
6 |
|
Telnet |
Telecommunications Network |
Enables a workstation to emulate a terminal, for example to mainframes and microcomputers over the Networks. |
5-7 |
|
NFS |
Network File System |
Used to transfer file over a Network |
5-7 |
|
RPC |
Remote Procedure Call |
Enables a remote computer to execute procedures on another computer, such as a server |
|
|
HTTP |
Hypertext Transfer Protocol |
Used for World Wide Web communications |
6 |