Replication Database and File Servers
Appendixes:
The main purpose of this document is to identify the major uses
of bandwidth and their effects on the Philips Consumer Communications
(PCC) global network. In some cases further research needs to
be performed to quantitatively identify precisely the order of
significance of a bandwidth consumer or to identify any other
major uses of the network which have not been included within
this document. To perform this research, network monitoring
should be employed. This will require the cooperation of Lucent,
Philips and perhaps third parties, such as MCI and Origin, which
control parts of the network.
This document takes into consideration that Frame Relay will be
employed for the network. A discussion of Frame Relay is
included as are definitions of terms associated
with Frame Relay.
Care must be taken when looking at each use of the network as
a stand alone application. The entire set of uses of bandwidth
must be viewed as working together in the context of a living
organism which must survive within the boundaries of the network.
Some applications of the network are critical to the performance
of the business while others may affect productivity or be highly
visible to the users, both internal and external to the business.
A chart is included to show Application Significance.
E-Mail usually is thought of as many small messages set from
people or processes to other people or processes. In this context
e-mail has very little impact on a network unless there exits
constant e-mail activity with large numbers of senders and recipients
all active at the same time. Such activity does occur when people
arrive at work around the same time and read and reply to e-mail
as their first task of the day.
E-Mail can also be the method of choice for transferring file attachments between client machines. In this case e-mail offers a simple, convenient, process to share files and, as such, may be employed over the standard file transfer procedures chosen by the organization. The result can be short large bursts of activity over the network. Such is the case if a person or process uses e-mail to distribute a daily multi-megabyte file to a number of people . The result can be the virtual shutdown of network access to the sending site.
Internet access can be one of the most taxing activities over
the network. The graphical nature of browsing lends itself to
downloading large items of data and the home page concept begs
users to continue requesting additional content.
When only a few users are using the Internet at the same time
the impact to the network can be relatively small depending on
the bandwidth of the connection to the Internet relative to the
user's needs. There are, even in the case of a small number of
Internet users, some important concerns when looking at network
bandwidth available to non Internet users over the network. These
include whether or not the access to the Internet is direct from
the local site or through the global network of the organization,
in the case of Internet access through the global network: the
total bandwidth of the site to the outside community, and the
amount of activity of the users with respect to the Internet.
A situation where two or three simultaneous users of the Internet
can cause a virtual shutdown of a site's access to the global
network would be if the site's access to the Internet was through
the global network and the connection's bandwidth was of the magnitude
of two or three times the normal point to point access of a single
user to the Internet and two or three users were downloading an
adequate amount of data to saturate the bandwidth of the network
connection.
There are, even in the case of a small number of users, some important concerns when looking at network bandwidth available to (other) users over the network.
In particular, it should be noted whether or not the access to the Internet is direct from the local site or through the global network of the organization. Where users access the Internet through the global network, the total bandwidth of the site to the outside community and the amount of activity of the users with respect to the Internet are critical considerations. Two or three simultaneous Internet users could cause a virtual shutdown of the global network if:
With each site having its own link into the Internet rather than through the global network, the impact of Internet activity on the global network is greatly, but not completely reduced. Items impacting this are the configuration and use of proxy servers and Internet servers, on the global network, which link to other servers on the global network, and the sharing of downloaded content form the Internet over the global network.
Sherpa provides documents, data, and design files to users by
archiving an entire directory of related documents and sending
them as one tar file over the network. Since the major intended
use of Sherpa is to be the vault of the engineering documents,
which include drawings related to each product, these directories
and the resulting tar files can be quite large ( often greater
than 200 MB). Such transfers of large files over the global network
can, at best, slow down the other activity of the network. At
worst, they can cause a virtual shutdown of a site's access to
the global network during the time of the transfer. Care should
be given to the global access bandwidth of a site containing a
Sherpa server which services the global community.
Special consideration should be given to the transfers of Sherpa tar files over a frame relay network. By the very nature of frame relay, large files can have their frames tagged with a Discard Eligibility (DE) bit that will allow them to be thrown out if there is not enough bandwidth to let them through. In this case an entire transmission could be thrown out and required to start over again. By using a protocol such as TCP/IP this process can be automatic and not seen by the user.
SAP is the primary ERP system of PCC and as such interfaces to
most of the other applications which depend on the network. SAP
network traffic ranges from many small transfers of data to relatively
large feeds to such applications as the Data Warehouse.
In addition to the internal requirements, there will be external
interfaces to SAP that will involve business partners of PCC.
This activity occurs primarily via Electronic Data Interchange,
but could occur via direct interfaces and potentially via the
Internet.
Some applications can not perform their activity without feeds from SAP. In some cases these feeds from SAP are mission critical and can not tolerate neither network down time nor delays in transversing the network.
Video over the network is currently driven from a Public
Relations perspective. The *avi files supplied by the http://bettertogether.cp.lucent.com
rank 5 in download popularity are number 1 in KB transferred by
a factor of 2. There is a moratorium on the use of *.avi files
for the short-term to allow the CIO organization time to find
the right answers to handling this demand on the network.
Potentially, video will be employed in several applications ranging
from remote surveillance for security, process observation, and
educational videos to desktop and multicast video conferencing.
Remote surveillance will range from sampling at preset intervals
and video presented upon the occurrence of an event such as a
person logging onto a client machine, to constant video feeds
over the network. The impact on the network bandwidth requirements
will vary by the implementation of remote surveillance.
Educational videos will be either downloaded and then viewed or
viewed in real time over the network. Again, the impact on bandwidth
requirements will vary by the amount of such usage.
Desktop video conferencing will involve voice and video as well
as other data transfer required by complementary applications
such as white boarding. As people adopt this form of communication
to replace traveling to meetings and telephone calls, the bandwidth
requirements, of the global network, for this activity will grow.
Although frame relay is not designed for video transmissions, the quality of these transmissions can be seen as similar to that which is experienced over the Internet.
Other traffic generating applications and activities that together
will have bandwidth intensive requirements:
As more and more applications support browser based clients the
bandwidth needs of these applications will grow. With a browser
based client the activity of the application to supply the images
and text to the screen will be the same as that of any Internet
type of access. The client will normally not have any local processing
based on the data. This processing will be at the server which
will only send the results to be displayed on the screen. This
will be the case when the clients are network computers and also
is currently the case in several applications currently in use.
The major concerns for bandwidth will be at the connection of the server site into the global network. In the case of local server based browser client software the major concern will be with the local area network.
Cognos Powerplay Cubes are representations of data from a database
that allow a user to "slice and dice" views of data
without directly hitting the database. This reduces the activity
on the database server and its network connection. A Powerplay
Cube can be delivered directly to a client machine via e-mail,
placed on a shared network drive, or viewed with a browser when
served by Cognos Powerplay Server software.
Since these cubes contain all the data from the database that
is in the scope of their purpose (i.e. sales data), their size
is usually in the multi megabyte range. If they are delivered
via e-mail to multiple people, over the global network at the
same time, the traffic could result in the virtual shutdown of
network access to the sending site.
If the cubes are viewed with a browser by multiple clients at the same time, the impact on the network would be the same as any other browser based activity, including the impact seen at the server site.
The network bandwidth requirements for ASPECT are, as yet, to be determined. However this application will require reliable access over the global network.
The bandwidth requirements for mainframe connectivity will be determined after a proper analysis of current network usage with adjustments for changes in current usage.
MES is primarily a local application which receives feeds from some other non-local data sources such as SAP. The bandwidth requirements are more in the nature of being critical than data intensive.
Replication
Database and File Servers
Replication Database and File Servers will require approximately double the bandwidth used to access a single server. The reason is that for each write to a server an additional write will be made to its replication server, thus keeping a redundant copy of the database and files. Since this is primarily a write and synchronization process it does not require double the read activity.
Remote access should have the same network bandwidth requirements as any other site on the global network as long as the following assumptions are made. The remote access will be through regional sites on the global network where dial in points will attach to the network.
Definitions of Terms
Mission Critical: Applications that are critical to the
running of the business. Were they not available, a manufacturing
process or some other critical business activity would halt.
High Visibility: Applications that are used by many people,
either from inside the company or from the outside such as customers,
suppliers, and the general public. Were such applications not
available, many people would be aware of the problem and such
activities as customer service, public relations, etc. could halt.
High Productivity: Applications which contribute to the
productivity of the company and its workforce. Were such applications
not available, productivity would be negatively affected. In
some cases, workers could be sitting idle while a high productivity
application was not available.
| Mission
Critical | High
Visibility | High
Productivity | |
| Internet Activity | |||
| MFG/Pro | |||
| Sherpa | |||
| SAP | |||
| Video | |||
| Browser Based Clients | |||
| COGNOS POWERPLAY CUBES | |||
| COSMOS ( ASPECT) | |||
| Mainframe connectivity | |||
| MES | |||
| Replication Database and File Servers | |||
| Remote Access | |||
| Lucent Common Systems |
Changes in the above chart will be required as more people review
this content.
Frame Relay is
a simplified form of Packet Switching similar
in principle to X.25 in which synchronous frames of data are routed
to different destinations depending on header information.
The biggest difference between Frame Relay and X.25 is that X.25
guarantees data integrity and network managed flow control at
the cost of some network delays. Frame Relay switches packets
end to end much faster, but there is no guarantee of data integrity.
Frame Relay is cost effective, partly due to the fact that the
network buffering requirements are carefully optimized. Compared
to X.25, with its store and forward mechanism and full error correction,
network buffering is minimal. Frame Relay is also much faster
than X.25: the frames are switched to their destination with only
a few byte times delay, as opposed to several hundred milliseconds
delay on X.25.
Frame Relay uses the synchronous HDLC frame format (see Synchronous and Asynchronous Communications) up to 4kbytes in length. Each frame starts and ends with a Flag character (7E Hex). The first 2 bytes of each frame following the flag contain the information required for multiplexing across the link. The last 2 bytes of the frame are always generated by a Cyclic Redundancy Check (CRC) of the rest of the bytes between the flags. The rest of the frame contains the user data.
Virtual Circuits
Packets are routed through one or more Virtual Circuits known as Data Link Connection Identifiers (DLCIs). Each DLCI has a permanently configured switching path to a certain destination. Thus, by having a system with several DLCIs configured, you can communicate simultaneously with several different sites. Currently, only permanent virtual circuit connections are supported. This means that all DLCI connections are set up by the network provider at subscription time.
Data Integrity
There is none, however, the network delivers data quite reliably.
Unlike the analog communication lines that were originally used
for X.25, modern digital lines have very low error rates. In practice,
very few frames are discarded by the network, particularly at
this time when the networks are operating at well below design
capacity.
The network delivers frames, whether the CRC check matches or not. It does not even necessarily deliver all frames, discarding frames whenever there is network congestion. Thus it is imperative to run an upper layer protocol above Frame Relay that is capable of recovering from errors, such as HDLC, IPX or TCP/IP.
Flow control and Information rates
There is no flow control on Frame Relay. The network simply discards
frames it cannot deliver.
When you subscribe, you will specify the line speed (e.g. 56kbps or T1) and also, typically, you will be asked to specify a Committed Information Rate (CIR) for each DLCI. This value specifies the maximum average data rate that the network
undertakes to deliver under "normal conditions". If
you send data faster than that on a given DLCI, the network will
flag some frames with a Discard Eligibility (DE) bit.
The network will do its best to deliver all packets but will discard
any DE packets first if there is congestion. Many inexpensive
Frame Relay services are based on a CIR of zero. This means that
every frame is a DE frame, and the network will throw them away
when it needs to.
Frame Relay provides indications that the network is becoming congested by means of the Forward Explicit Congestion Notification (FECN) and Backward Explicit Congestion Notification (BECN) bits in data frames. These are used to tell the application to slow down, hopefully before packets start to be discarded.
Status polling
The Frame Relay Customer Premises Equipment (CPE) polls the switch
at set intervals to find out the status of the network and DLCI
connections. A Link Integrity Verification (LIV) packet exchange
takes place about every 10 seconds, which verifies that the connection
is still good. It also provides information to the network that
the CPE is active, and this status is reported at the other end.
About every minute, a Full Status (FS) exchange occurs, which
passes information on which DLCIs are configured and active. Until
the first FS exchange has occurred, the CPE does not know which
DLCIs are active, and so no data transfer can take place.
Frame Relay is used mostly to route Local Area Network protocols such as IPX or TCP/IP. It can also be used to carry asynchronous traffic, SNA or even voice data. Its primary competitive feature is its low cost. In North America it is fast taking
on the role that X.25 has had in Europe: the most cost effective
way to hook up multiple stations with high speed digital links.
Frame Relay networks do not yet have the reliability of X.25 networks. Expect problems with new installations. You cannot take any features for granted, not even the ability of the network to transfer transparent data. At the time of writing, some public networks do not support LIV polling properly. This makes it difficult to find out whether remote links are up or not.
A communications line (e.g., circuit) interconnecting a frame-relay-compatible
device (DTE) to a frame-relay switch (DCE). See also Trunk Line.
Return to Table of Contents
The data rate of the user access channel. The speed of the access channel determines how rapidly (maximum rate) the end user can inject data into a frame relay network.
American National Standards Institute (ANSI)
Devises and proposes recommendations for international communications standards. See also Comite Consultatif International Telegraphique et Telephonique (CCITT).
Backward Explicit Congestion Notification (BECN)
A bit set by a frame relay network to notify an interface
device (DTE) that congestion avoidance procedures should be initiated
by the sending device. Return to Table of Contents
The range of frequencies, expressed in Kilobits per second, that can pass over a given data transmission channel within a frame relay network. The bandwidth determines the rate at which information can be sent through a channel - the greater the bandwidth, the more information that can be sent in a given amount of time.
A device that supports LAN-to-LAN communications. Bridges may be equipped to provide frame relay support to the LAN devices they serve. A frame-relay-capable bridge encapsulates LAN frames in frame relay frames and feeds those frame relay frames to a frame relay switch for transmission across the network. A frame-relay-capable bridge also receives frame relay frames from the network, strips the frame relay frame off each LAN frame, and passes the LAN frame on to the end device. Bridges are generally used to connect local area network (LAN) segments to other LAN segments or to a wide area network (WAN). They route traffic on the Level 2 LAN protocol (e.g., the Media Access Control address), which occupies the lower sub layer of the LAN OSI data link layer. See also Router.
In the context of a frame relay network, data that uses bandwidth
only sporadically; that is, information that does not use the
total bandwidth of a circuit 100 percent of the time. During pauses,
channels are idle; and no traffic flows across them in either
direction. Interactive and LAN-to-LAN data is bursty in nature,
because it is sent intermittently, and in between data transmissions
the channel experiences idle time waiting for the DTEs to respond
to the transmitted data user's input of waiting for the user to
send more data. Return to Table of Contents
Generically refers to the user access channel across which frame relay data travels. Within a given T1 or E1 physical line, a channel can be one of the following, depending upon how the line is configured.
Unchannelized - The entire T1/E1 line is considered a channel, where:
The T1 line operates at speeds of 1.536 Mbps and is a single channel consisting of 24 T1 time slots.
The E1 line operates at speeds of 1.984 Mbps and is a single channel consisting of 20 E1 time slots.
Channelized - The channel is any one of N time slots within a given line, where:
The T1 line consists of any one or more channels. Each channel is any one of 24 time slots. The T1 line operates at speeds in multiples of 56/64 Kbps to 1.536 Mbps, with aggregate speed not exceeding 1.536Mbps.
The E1 line consists of one or more channels. Each channel is any one of 31 time slots. The E1 operates at speeds in multiples of 64 Kbps to 1.984 Mbps, with aggregate speed not exceeding 1.984 Mbps.
Fractional - The T1/E1 channel is one of the following groupings of consecutively or non-consecutively assigned time slots:
N T/1 time slots (NX56/64Kbps where N = 1 to 23 T1 time slots per FT1 channel).
N E1 time slots (NX64Kbps, where N = 1 to 30 time slots per E1 channel).
An ancillary device needed to adapt the V.35 interface on a F.R. DTE to the T1 (or E1) interface on a frame relay switch. The T1 (or E1) signal format on the frame relay switch is not compatible with the V.35 interface on the DTE: therefore, a CSU or similar device, placed between the DTE and the frame relay switch, is needed to perform the required conversion.
The maximum amount of data (in bits) that the network agrees to transfer, under normal conditions, during a time interval Tc. See also Excess Burst Size (Be).
Comite Consultatif International Telegraphique et Telephonique (CCITT)
International Consultative Committee for Telegraphy and Telephony, a standards organization that devises and proposes recommendations for international communications. See also American National Standards Institute (ANSI).
Committed Information Rate (CIR)
The committed rate (in bits per second) at which the ingress
access interface trunk interfaces, and egress access interface
of a frame relay network transfer information to the destination
frame relay end system under normal conditions. The rate is averaged
over a minimum time interval Tc.
Return to Table of Contents
Committed Rate Measurement Interval (Tc)
The time interval during which the user can send only Bc-committed amount of data and Be excess amount of data. In general, the duration of Tc is proportional to the "burstiness" of the traffic. Tc is computed (from the subscription parameters of CIR and Bc) as Tc =Bc/CIR. Tc is not a periodic time interval. Instead, it is used only to measure incoming data, during which it acts like a sliding window. Incoming data triggers the Tc interval, which continues until it completes its commuted duration. See also Committed Information Rate (CIR) and committed Burst Size (Bc).
A computational means to ensure the accuracy of frames transmitted between devices in a frame relay network. The mathematical function is computed, before the frame is transmitted, at the originating device. Its numerical value is computed based on the content of the frame. This value is compared with a re-computed value of the function at the destination device. See also Frame Check Sequence (FCS).
Data Communications Equipment (DCE)
Term defined by both frame relay and X.25 committees, that applies to switching equipment and is distinguished from the devices that attach to the network (DTE). Also see DTE.
Data Link Connection Identifier (DLCI)
A unique number assigned to a PVC end point in a frame relay
network. Identifies a particular PVC endpoint within a user's
access channel in a frame relay network and has local significance
only to that channel. Return to Table of Contents
A user-set bit indicating that a frame may be discarded in preference to other frames if congestion occurs, to maintain the committed quality of service within the network. Frames with the DE bit set are considered Be excess data. See also Excess burst Size (Be).
Frame relay frames leaving a frame relay network in the direction toward the destination device. Contrast with Ingress.
The ultimate source or destination of data flowing through a frame relay network sometime referred to as a Data Terminal Equipment (DTE). As a source device, it sends data to an interface device for encapsulation in a frame relay frame. As a destination device, it receives de-encapsulated data (i.e., the frame relay frame is stripped off, leaving only the user's data) from the interface device. Also see DCE.
NOTE: An end device can be an application program or some operator-controlled device (e.g., workstation). In a LAN environment, the end device could be a file server or host.
A process by which an interface device places an end device's protocol-specific frames inside a frame relay frame. The network accepts only frames formatted specifically for frame relay; hence, interface devices acting as interfaces to a frame relay network must perform encapsulation. See also Interface device or Frame-Relay-Capable Interface Device.
The maximum amount of uncommitted data (in bits) in excess of Bc that a frame relay network can attempt to deliver during a time interval Tc. This data (Be) generally is delivered with a lower probability than Bc. The network treats Be data as discard eligible. See also Committed burst Size (Bc).
Transmission rate of 2.048 Mbps on E1 communications lines.
An E1 facility carriers a 2.048 Mbps digital signal. See also
T1 and channel.
Return to Table of Contents
In the context of frame relay network supporting LAN-to-LAN communications, a device connecting a series of workstations within a given LAN. The device performs error recovery and flow control functions, as well as end-to-end acknowledgment of data during data transfer, thereby significantly reducing overhead within the frame relay network.
Forward Explicit Congestion Notification (FECN)
A bit set by a frame relay network to notify an interface device (DTE) that congestion avoidance procedures should be initiated by the receiving device. See also BECN.
The standard 16-bit cyclic redundancy check used for HDLC and frame relay frames. The FCS detects bit errors occurring in the bits of the frame between the opening flag and the FCS, and is only effective in detecting errors in frames no larger than 4096 octets. See also Cyclic Redundancy Check (CRC).
Frame-Relay-Capable Interface Device
A communications device that performs encapsulation. Frame-relay-capable routers and bridges are examples of interface devices used to interface the customer's equipment to a frame relay network. See also Interface Device and Encapsulation.
A variable-length unit of data, in frame-relay format that is transmitted through a frame relay network as pure data. Contrast with Packet. See also Q.922A.
A telecommunications network based on frame relay technology.
Data is multiplexed. Contrast with Packet-Switching Network. Return to Table of Contents
High Level Data Link control (HDLC)
A generic link-level communications protocol developed by the International Organization for Standardization (ISO).
HDLC manages synchronous, code-transparent, serial information
transfer over a link connection. See also Synchronous Data Link Control (SDLC).
Return to Table of Contents
A single trunk line between two switches in a frame relay network. An established PVC consists of a certain number of hops, spanning the distance from the ingress access interface to the egress access interface within the network.
A communications device that enables people to run applications programs to perform such functions as text editing, program execution, access to databases, etc.
Frame relay frames from an access device toward the frame relay network. Contrast with Egress.
Provides the interface between the end device(s) and a frame relay network by encapsulating the user's native protocol in frame relay frames and sending the frames across the frame relay backbone. See also Encapsulation and Frame-Relay-Capable Interface Device.
Link Access Procedure Balanced (LAPB)
The balanced-mode, enhanced, version of HDLC. Used in X.25 packet-switching networks. Contrast with LAPD.
Link Access Procedure on the D-channel (LAPD)
A protocol that operates at the data link layer (layer 2) of the OSI architecture. LAPD is used to convey information between layer 3 entities across the frame relay network. The D-channel carries signaling information for circuit switching. Contrast with LAPB.
A privately owned network that offers high-speed communications
channels to connect information processing equipment in a limited
geographic area. Return to Table of Contents
A range of LAN protocols supported by a frame relay network, including Transmission Control Protocol/Internet Protocol (TCP/IP), Apple Talk, Xerox Network System (XNS), Internetwork Packet Exchange (IPX), and Common Operating System used by DOS-based PCs.
In the context of a frame relay network supporting LAN-to-LAN communications, a LAN linked to another LAN by a bridge. Bridges enable two LANs to function like a single, large LAN by passing data from one LAN segment to another. To communicate with each other, the bridged LAN segments must use the same native protocol. See also Bridge.
A group of fixed-length binary digits, including the data and call control signals, that are transmitted through an X.25 packet-switching network as a composite whole. The data, call control signals, and possible error control information are arranged in a predetermined format. Packets do not always travel the same pathway but are arranged in proper sequence at the destination side before forwarding the complete message to an addressee. Contrast with Frame Relay Frame.
A telecommunications network based on packet-switching technology, wherein a transmission channel is occupied only for the duration of the transmission of the packet. Contrast with Frame Relay Network.
A numerical code that controls an aspect of terminal and/or network operation. Parameters control such aspects as page size, data transmission speed, and timing options.
Permanent Virtual Circuit (PVC)
A frame relay logical link, whose endpoints and class of service are defined by network management. Analogous to an X.25 permanent virtual circuit, a PVC consists of the originating frame relay network element address, originating data link control identifier, terminating frame relay network element address, and termination data link control identifier.
Originating refers to the access interface from which the PVC is initiated. Terminating refers to the access interface at which the PVC stops. Many data network customers require a PVC between two points. Data terminating equipment with a need for continuous communication use PVCs. See also Data Link Connection Identifier (DLCI).
The international draft standard that defines the structure of frame relay frames. Based on the Q.922A frame format developed by the CCITT. All frame relay frames entering a frame relay network automatically conform to this structure.
Contrast with Link Access Procedure Balanced (LAPB). Return to Table of Contents
A variable-length unit of data, formatted in frame-relay
(Q.922A) format, that is transmitted through a frame relay network
as pure data (i.e., it contains no flow control information ).
Contrast with Packet. See also Frame Relay Frame.
Return to Table of Contents
A device that supports LAN-to-LAN communications. Routers
may be equipped to provide frame relay support to the LAN devices
they serve. A frame-relay-capable router encapsulates LAN frames
in frame relay frames and feeds those frame relay frames to a
frame relay switch for transmission across the network. A frame-relay-capable
router also receives frame relay frames from the network, strips
the frame relay frame off each frame to product the original LAN
frame, and passes the LAN frame on to the end device. Routers
connect multiple LAN segments to each other or to a WAN. Routers
route traffic on the Level 3 LAN protocol (e.g., the Internet
Protocol address). See also Bridge.
Return to Table of Contents
Interleaving the data input of two or more devices on a single channel or access line for transmission through a frame relay network. Interleaving of data is accomplished using the DLCI.
Synchronous Data Link Control (SDLC)
A link-level communications protocol used in an International
Business Machines (IBM) Systems Network Architecture (SNA) network
that manages synchronous, code-transparent, serial information
transfer over a link connection. SDLC is a subset of the more
generic High-Level Data Link Control (HDLC) protocol developed
by the International Organization for Standardization (ISO). Return to Table of Contents
Transmission rate of 1.544 Mbps on T1 communications lines. A T1 facility carriers a 1.544 Mbps digital signal. Also referred to as digital signal level 1 (DS-1). See also E1 and channel.
A communications line connecting two frame relay switches
to each other. Return to Table of Contents
The above material on Frame Relay was taken from the following site:
which is the property of Sangoma Technologies Inc.
For a glossary on Frame Relay refer to the following site:
http://www.cisco.com/warp/public/74/87.html
which is the property of Cisco Systems, Inc.
A site that contains valuable information, including white papers, on Frame Relay is the Frame Relay Forum:
Use of the terms "Users", "People", and "Processes":
Users are logged in entities which have one or more of the following traits:
Tie up a licensed unit of software, either concurrent or named
Tie up a client machine
Are counted by software as a user
People are considered as humans which are users
Processes are non human entities which can be users