inverse multiplexer -- Equipment
that performs inverse multiplexing at each end of a connection.
An inverse multiplexer is also known as an inverse mux.
I-NLSP
-- Integrated Net Layer Security Protocol
Internet gateway
-- A gateway (see Gateway) for accessing the
Internet, which is loosely defined as the complex of wide area
networks joining government, university, corporate and private
computers (nodes) in a vast web of network interconnection.
interoperability
-- Interoperable devices are compatible with
the devices and services of multiple vendors, and can be integrated
into a generic network containing a wide range of vendor products.
Interoperability is a significant factor among expansion considerations,
since any device must have the versatility to function in an expanding
network structure. The technical elements of interoperability
may include a bundle of protocols and a flexible architecture
to accommodate upgrades. A remote access server should include
capabilities such as translation, encapsulation, filtering, etc.,
that enable internetworking.
inverse multiplexing
-- A multiplexer is an electronic device that
enables two or more signals to pass over a single communications
circuit, whether analog or digital. An inverse multiplexer allows
individually dialed channels across a network to be combined into
a single, higher-speed data stream. Each end of the connection
uses an inverse multiplexer, or inverse mux.
For example, suppose one site has three ISDN BRI
lines connected to an inverse mux and another site has a T1 access
line connected to an inverse mux. The user at the first site can
place a 336 kbps call to the second site using inverse multiplexing.
Because each BRI line has two 64 kbps channels (with 56 kbps reserved
for data on each channel), the inverse mux places six individual
calls over Switched-56 services to the answering T1-based inverse
mux. The two inverse muxes combine the six calls into a single
data stream at 336 kbps (6X56 kbps).
There are two types of inverse multiplexing: packet-level
inverse multiplexing and circuit-level inverse multiplexing.
In packet-level inverse multiplexing, the inverse
mux performs its function at the packet level using the MP or
MPP protocol. One data packet goes over the first circuit, the
next goes over the second circuit, and so on, until all the data
packets are distributed over all the available circuits. The receiving
end adjusts for network-induced delay and reassembles the data
packets into their proper order. This inverse multiplexing technique
is also referred to as load balancing. Telecommuting applications
use packet-level inverse multiplexing.
In circuit-level inverse multiplexing, the inverse
mux slices the data stream into equal portions, and transmits
each portion over an available circuit. The receiving end adjusts
for network-induced delay and reassembles the data packets into
their proper order. The AIM and BONDING protocols define how circuit-level
inverse multiplexing works. Applications that require transparent
digital circuits, such as videoconferencing, nailed-up backup
and overflow, and bulk file transfer applications, use circuit-level
multiplexing.
inverse mux
-- An inverse multiplexer.
IP --
Internet Protocol
IP address
-- An address that uniquely identifies each
host on a network or internet.
An IP address has a length of 32 bits, and is divided
into four 8-bit parts, each separated by a period, as in 149.122.3.30.
This kind of notation is called dotted decimal notation. Each
part can consist of a number between 1 and 255.
An IP address consists of a network number and a
host number. IP addresses come in three types: Class A, Class
B, and Class C. The class of an IP address determines which portion
of the address belongs to the network number and which portion
belongs to the host number. The first bits of the IP address identify
the class. The Internet's Network Information Center (NIC) determines
the type of class assigned a network.
A Class A address starts with 0 as the class identifier,
followed by 7 bits for the network number and 24 bits for the
host number. Therefore, the first number in dotted decimal form
is the network number; the next three numbers make up the host
number. For example, in the IP address 127.120.3.8, the network
number is 127 and the host number is 120.3.8. This type of address
is used by the largest organizations, because this scheme allows
for over 16 million different host numbers. However, it also limits
network numbers to a total of 128.
A Class B address starts with binary 10 as the class
identifier, followed by 14 bits for the network number and 16
bits for the host number. Therefore, the first two dotted decimal
numbers comprise the network number, and the second two dotted
decimal numbers comprise the host number. For example, in the
IP address147.14.86.24, the network number is 147.14 and the host
number is 86.24. More network numbers are available, but fewer
hosts (approximately 65,000).
A Class C address starts with binary 110 as the class
identifier, followed by 21 bits for the network number and 9 bits
for the host number. Therefore, the first three dotted decimal
numbers comprise the network number, and the last dotted decimal
number comprises the host number. For example, in the IP address
225.135.38.42, the network number is 225.135.38 and the host number
is 42. Many network numbers are available, but only 254 hosts
per network number. The numbers 0 and 255 are reserved.
You can tell the type of class an IP address falls
into by looking at the first 8-bit portion of the dotted decimal
form of the address. Class A addresses begin with a number between
0 and 127. Class B addresses begin with a number between 128 and
223. Class C addresses begin with a number between 192 and 233.
In addition to an IP address, you can use a symbolic
name provided by Domain Name Services (DNS) to designate an Internet
address.
IP filters
-- When defining filters, you can set the
Type of filter to Generic or IP. If you set the type to IP, the
filter can examine a TCP/IP/UDP data packets' source addresses,
destination addresses, IP protocol type, port, or any combination
of these.
IP subnet
-- Internet Protocol subnet. An IP subnet
or subnet mask is a way to subdivide a network into smaller networks,
so you can have a greater number of computers on a network with
a single IP address. The IP subnet is a number that you append
to the IP address. For example, 195.112.56.75/14, 195.112.56.75/15,
and 195.112.56.75/16 are all IP addresses with subnets of 14,
15, and 16.
IP switch
--
A high-performance device designed for high-volume, large-scale public and private backbone applications. A switch is a device that can determine the destinations of large volumes of incoming packets and send them to the appropriate output ports at high speeds.
IPCP (Internet Protocol Control
Protocol) -- Internet
Protocol Control Protocol is responsible for configuring, enabling
and disabling the IP protocol modules on both ends of a point-to-point
link. The IP Control Protocol is tied to PPP, and is activated
only when PPP reaches the network layer protocol phase. If IPCP
packets are received prior to this phase, they should be discarded.
Elements of IPCP include packet encapsulation, code fields and
timeouts.
IPCU --
Internet Packet Core Utility
IPIP --
IP-within-IP Encapsulation Protocol
IPPC --
Internet Pluribus Packet Core
IPX (Internet Packet Exchange)
-- Internet Packet eXchange , the NetWare
LAN communications protocol used to move data between servers
and workstation programs running on various network nodes. IPX
packets are encapsulated and carried by Ethernet packet and Token
Ring frames as appropriate.
IPX spoofing
-- This is a procedure used by hackers and
other unauthorized users which enables a user to mimic a legitimate
network node, then gain access to data within a private network.
Spoofing can lead to severe security breaches and damage to the
integrity of a company's operations.
IPXCP --
Fulfills the same function as IPCP, but for IPX routing.
See IPCP.
IPXWAN
-- The WAN version of NetWare's IPX protocol.
IRTP --
Internet Reliable Transport Protocol
ISDN (Integrated Services Digital
Network) -- Integrated
Services Digital Network. A system that provides simultaneous
voice and high-speed data transmission through a single channel
to the user's premises. ISDN is an international standard for
end-to-end digital transmission of voice, data, and signaling.
ISDN BRI line
-- An ISDN Basic Rate Interface line that
uses two B channels for user data, and one 16-kbps D channel for
ISDN D-channel signaling. Both B channels can be switched, both
channels can be nailed up, or one channel can be switched and
the other nailed up. BRI stands for Basic Rate Interface. A line
of this type can connect to standard voice service, Switched-56
data service, or Switched-64 data service.
ISDN D-channel signaling
-- A type of signaling in which a D channel
handles WAN synchronization and signaling, and the B channels
carry the user data. Another term for ISDN D-channel signaling
is out-of-band signaling. T1 PRI, E1 PRI, and ISDN BRI lines
use ISDN D-channel signaling.
ISO 9001
-- ISO is the International Standards Organization,
and is devoted to the definition of standards for international
and national data communications. (The U.S. representative to
the ISO is ANSI.3.) 9001 is the current set of ISO standards.
Companies whose products are ISO certified reflect a high quality
of consistency and quality.
ISO-IP
-- International Standards Organization Internet
Protocol
ISO-TP4
-- International Standards Organization Transport
Protocol Class 4
ISP (Internet Service Provider)
-- An Internet Service Provider is a company
that provides access to the Internet. By establishing Points of
Presence (POPs) containing remote access servers and additional
devices, as well as a suite of user software packages, the Internet
Service Provider acts as a commercial Internet on-ramp. Providers
typically charge a monthly fee and supply technical support and
advice to customers.
IXC --
Interexchange Carrier
Java
--
An object-oriented programming language developed by Sun Microsystems, Inc. used to create applets that can be distributed over the World Wide Web. Java programs run inside a Java-enabled Web browser; otherwise they run inside a Java Virtual Machine (JVM).
kbps --
kilobits per second
LAN (Local Area Network)
-- A network that interconnects devices over
a geographically small area, typically in one building or a part
of a building. The most popular LAN type is Ethernet, a 10 Mbps
standard that works with 10BaseT, 10Base2, or 10Base5 cables.
When you interconnect a single computer to the Pipeline with the
crossover cable in your package, you are creating a two-node Ethernet
network.
LAN packet display
-- This is a display of packet performance
over a specified time, whether measured graphically or by counters.
LAN/WAN connectivity
-- This is the practical set of tools, from
OS layer protocols to support services, that make a remote access
device an effective link between LANs and WANs. An effective remote
access server must include a host of communications and translation
protocols to fulfill this function.
LAP-B
--
A protocol called Link Access Procedure for B channels using packet switching mode.
LAP-D
--
Link Access Protocol for the D channel. The protocol provides the setup mechanism to combine multiple channels into a single logical link as well as the normal administrative tasks of monitoring and controlling the flow of data over the B channels.
LAP-F
--
A protocol called Link Access Procedure for Frame-mode bearer services.
LARP --
Locus Address Resolution Protocol
latency
--
The minimum time required to move data from one point to another. Things that contribute to latency are:
- Physical media, such as the time it takes electricity to go through copper, or light to go through fiber, plus physical interference from noise or other signals.
- Set-up and tear-down time required regardless of the duration of a connection.
- Signal interfaces, such as Ethernet, which consumes a minimum of 0.3 milliseconds (ms), or a 28.8 modem, which takes about 300 times longer.
- Bottlenecks, such as the 50 ms it takes to squeeze data through a serial port.
- Data conversions, such as digital to analog and analog to digital required by modems.
- Compression, which may be unnecessary if you are only sending one or two characters, since the algorithm waits for data to yield better compression ratios.
Once latency is present, it cannot be optimized. The cause has to be removed (as in using an internal device rather than an external serial device to remove the latency caused by the serial port). To maximize throughput, use the highest bandwidth available. Assume ‘band speed’ to be constant--that is, all services go as fast as the medium allows.
For example, if the medium is copper, regardless if you are connecting to a T1 line or a single, digital voice line, the speed of the electrical signal through the copper is the same. The reason the T1 line is considered ‘faster’, is because its capacity (bandwidth) is greater (wider).
leased lines
-- A circuit rented for exclusive use twenty-four
hours a day, seven days a week from a telephone company. The connection
exists between two predetermined points and cannot be switched
to other locations.
LEC --
Local Exchange Carrier
line --
A physical interface to the WAN.
LLB --
Line Loopback
LLC --
Logical Link Control
loopback
-- A test that enables the Ascend unit to
place a call to itself over the WAN, and to send a user-specified
number of packets over the connection. The loopback tests the
Ascend unit's ability to initiate and receive calls, and diagnoses
whether the connection over the digital access line and the WAN
is sound. A local loopback can test whether the connection to
local devices is sound.
LQM (Line Quality Monitoring)
-- A feature that enables the Ascend unit
to monitor the quality of a link.
LQM counts the number of packets sent across the
link and periodically asks the remote end how many packets it
has received. Discrepancies are evidence of packet loss and indicate
link quality problems. The Ascend unit can tear down and reestablish
a call if the problems on the link exceed a specified threshold.
MAC (Media Access Control)
-- A system of rules used to move data from
one physical medium to another.
MB --
megabytes
MBONE
--
Multimedia Backbone
mbps --
megabits per second
MHRP --
Mobile Host Routing Protocol
MIB --
Management Information Base
MICP --
Mobile Internetworking Control Protocol
MIF --
Machine-to-Machine Interface Format
modem (MOdulator/DEModulator)
-- A DCE (Data Circuit-Terminating Equipment)
installed between a DTE (Data Terminal Equipment) and an analog
transmission channel, such as a telephone line. A DTE refers to
a device that an operator uses, such as a computer or a terminal.
The DCE connects the DTE to a communications channel, such as
a telephone line. A modem takes digital data from a DTE, translates
(or modulates) the 1s and 0s into analog form, and sends the data
over the channel. The receiving modem demodulates the analog signal
into digital data and sends it to the DTE to which it is attached.
MP (Multilink PPP)
-- A proposed standard for inverse multiplexing,
a method of combining individually dialed channels into a single,
higher-speed data stream. MP is an extension of PPP that supports
the ordering of data packets across multiple channels.
multiplexing
--
A method of letting users share one transmission line. In time division multiplexing, temporarily, each user has the full capacity of the line.
MPP (Multichannel Point-to-Point
Protocol) -- A protocol
that extends the capabilities of MP to support inverse multiplexing,
session management, and bandwidth management. MPP allows you to
combine up to 30 individual channels into a single high-speed
connection.
MPP consists of two components: a low-level channel
identification, error monitoring, and error recovery mechanism,
and a session management level for supporting bandwidth modifications
and diagnostics. MPP enables the Ascend unit to add or remove
channels from a connection as bandwidth needs change without disconnecting
the link. This capability is called Dynamic Bandwidth Allocation,
or DBA.
Both the dialing side and the answering side of the
link must support MPP. If only one side supports MPP, the connection
uses MP or standard single-channel PPP.
MPP calls cannot combine an ISDN BRI channel with
a channel on a T1 access line or a T1 PRI line.
MRRU
--
Maximum Reconstructed Receive Unit
MRU --
Maximum Receive Unit
MTP --
Multicast Transport Protocol
MTU --
Maximum Transfer Unit
multicast forwarding
--
A multicast forwarding table is built based on IGMP messages. Group memberships are created or refreshed in the multicast forwarding table. When IP multicast packets are received from the MBONE interface, the multicast forwarding table is used to distribute packets to multicast clients according to group membership. To communicate with multicast clients, IGMP queries are broadcast every 60 seconds, and based on responses, the table is updated.
MultiRate
-- A data service consisting of a single circuit
whose bandwidth is a multiple of 64 kbps. This circuit consists
of one or more B channels. For example, a user can dial a first
call at 384 kbps (using 6 B channels), and then dial at second
call at 512 kbps (using 8 B channels). This service is available
over T1 PRI lines only. MultiRate is also known as Switched Nx64
data service.
nailed line
-- A permanent connection between endpoints
over which two parties exchange data. A nailed line is also known
as a private line or a leased line.
NAS --
Network Access Server
NetWare call filter
-- A NetWare call filter is used to prevent
Service Advertising Protocol (SAP) packets originating on the
local IPX network from resetting the idle timer or initiating
a call.
NFAS --
Non-Facility Associated Signaling
NFAS (Non-Facility Associated signaling)
-- A special case of ISDN signaling in which
two or more T1 PRI lines use the same D channel, and you can add
a backup D channel. NFAS is required for Switched-1536 data service;
because all 24 channels of the T1 PRI line carry user data, the
D channel must be on another line.
NFS --
Network File System
NHRP --
Next Hop Resolution Protocol
NIC --
Network Information Center
NIS --
Network Information Service
NSFNET-IGP
-- National Science Foundation Network Interior
Gateway Protocol
NT1 (Network Terminator Type 1)
-- An ISDN BRI line terminating device at
the subscriber's location that provides line maintenance access,
timing, and echo cancellation. NT1s may be built into other pieces
of equipment or stand alone.
NVP-II
-- Network Voice Protocol II
NVT ASCII
-- Network Virtual Terminal ASCII
Octet --
Eight data bits.
OSI --
Open Systems Interconnection. A reference model used
to describe layers of a network and the types of functions expected
at each layer. The OSI model is used as a standard, letting developers
of networks and communication systems rely on the presence of
certain functions at certain places in a standard system.
Top to bottom, the seven layers are:
- application
- presentation
- session
- transport
- network
- data link
- physical
The physical and data link layers have to do with
hardware, wires, signals on wires, and basic addressing functions,
such as media access control (MAC). In the network layer, information
from different networking protocols is distinguished, which is
where the internet protocol (IP) functions. In the transport layer,
data is packaged for transport in a size and organization appropriate
for its intended environment. This is where transport control
protocol (TCP) works. The session, presentation, and application
layers keep information streaming in and convert it to a usable
format.
OSPF --
Open Shortest Path First
packets
--
A block of information sometimes called a cell, frame, data unit, service unit, or signaling unit. Although each of these elements do have unique attributes, in essence, all are packets.
packet-level inverse multiplexing
-- A method of inverse multiplexing in which
the inverse mux performs its function at the packet level using
the MP or MPP protocol. One data packet goes over the first circuit,
the next goes over the second circuit, and so on, until all the
data packets are distributed over all the available circuits.
The receiving end adjusts for network-induced delay and reassembles
the data packets into their proper order. This inverse multiplexing
technique is also referred to as load balancing. Telecommuting
applications use packet-level inverse multiplexing.
PAP (Password Authentication Protocol)
-- Password Authentication Protocol. A security
protocol that uses password protection to allow access to a network
or host.
parity
-- In 7-bit communication, each device sends
only the first 128 characters in the ASCII character set, because
each of these characters can be represented by seven bits or fewer.
Parity is a way for a device to determine whether it has received
data exactly as the sending device transmitted it. Each device
must determine whether it will use even parity, odd parity, or
no parity.
The sending device adds the 1s in each string it
sends and determines whether the sum is even or odd. Then, it
adds an extra bit, called a parity bit, to the string. If even
parity is in use, the parity bit makes the sum of the bits even;
if odd parity is in use, the parity bit makes the sum of the bits
odd. For example, if a device sends the binary number 1010101
under even parity, it adds a 0 (zero) to the end of the byte,
because the sum of the 1s is already even. However, if it sends
the same number under odd parity, it adds a 1 to the end of the
byte in order to make the sum of the 1s an odd number.
The receiving device checks whether the sum of 1s
in a character is even or odd. If the device is using even parity,
the sum of 1s in a character should be even; if the device is
using odd parity, the sums of bits in a character should be odd.
If the sum of the bits does not equal the parity setting, the
receiving device knows that an error has occurred during the transmission
of the data.
For special ASCII characters (128-256), eight bits
are necessary to represent the data. In 8-bit communication, no
parity bit is used.
PBX (Private Branch Exchange)
-- An internal telephone network, such as
those used in large offices, in which one incoming number directs
calls to various extensions and from one office to another.
PCM --
Pulse Coded Modulation
PDU --
Protocol Data Unit
Ping --
This is the command invoked on many systems to send
ICMP echo requests. Ping has several versions. The most sophisticated
Pings send a series of ICMP echo requests, capture responses,
and corollary statistics regarding data packet loss. The user
can determine the length of the ICMP request and designate an
interval between tries.
PLL --
Permanent Logical Link
PND --
Present Next Digit
Point to Point link
-- See Point-to-Point protocol (PPP).
POP (Point of Presence)
-- This is a point-of-presence of an Internet
service provider, used to facilitate remote users' access to the
range of applications and IP addresses in the internetwork.
port
--
A TCP/IP interface that defines a logical location in a computer where an application or process is running. By defining such a location, packets can be delivered to an application from a remote system, enabling remote interactivity.
There are certain ‘well-known ports’, such as port 21 used by FTP. Filters and firewalls make use of port addresses to restrict incoming and outgoing data and secure an environment.
The User Datagram Protocol (UDP) was developed to add the port address of an application or process to an IP packet, facilitating communication between applications over a network.
POST (Power-On Self Test)
-- A diagnostic test the Ascend unit performs
when it first starts up or after a system reset. While the yellow
FAULT LED on the front panel remains solidly lit, the Ascend unit
checks system memory, configuration, installed modules, and the
T1 connections. If the Ascend unit fails any of these tests, the
AFAULT (or CON) LED remains lit or blinks.
PPP (Point-to-Point Protocol)
-- Provides a standard means of encapsulating
data packets sent over a single-channel WAN link. It is the standard
WAN encapsulation protocol for the interoperability of bridges
and routers. PPP is also supported in workstations, allowing direct
dial-up access from a personal computer to a corporate LAN or
ISP. Using PPP ensures basic compatibility with non-Ascend devices.
Both the dialing side and the answering side of the link must
support PPP.
PRI --
Primary Rate Interface
PRM --
Packet Radio Measurement
promiscuous mode
-- A Bridging parameter mode that determines
that the Ethernet controller in the Ascend unit accepts all packets
and passes them up the protocol stack for a higher-level decision
on whether to route, bridge, or reject them. This mode is appropriate
if you are using the Ascend unit as a bridge.
protocol
-- A set of rules governing message exchange
over a network or internetwork. Examples of commonly used protocols
are TCP/IP (Transmission Control Protocol/Internet Protocol),
PPP (Point-to-Point Protocol), and IPX (Internet Packet Exchange).
proxy ARP
-- If the Pipeline is the default router on
a network, then packets destined for any of the hosts on the network
are sent to the Pipeline. If any of these hosts needs to respond
to an ARP request (a request to provide its physical address so
that a connection can be established), and the host is not on
the local network (ARP requests are only broadcast on a local
network), the Pipeline can respond on behalf of the remote host
to establish the connection. This is possible when the Pipeline
is set to function in Proxy Mode.
proxy mode
-- A remote host can be assigned an IP address
on the local network through its Connection profile on the Pipeline.
Local hosts on the network see the remote host as if it were on
the local network. When calls are made to the remote host, the
Pipeline acts on behalf of the remote host and replies to requests
and forwards packets. Proxy mode is enabled on the Pipeline via
the Protocols section of the configuration software.
PSDN
--
Packet-Switched Data Network. In a packet-switched network, no connection is required end-to-end. It is generally more efficient for data transfers and better for redundancy (where other circuits are automatically available if a line goes down).
PSTN
--
Public Switched Telephone Network
PVC --
Permanent Virtual Circuit. A path that is maintained by the stations at each end. The circuit is through the packet-switched mesh, but stays up all the time, regardless of whether or not data is being transmitted. The benefit of a PVC is that there is no circuit set up time, since it is always up.
PVC --
Protocol Version Control
PVP --
Packet Video Protocol
RADIUS (Remote Authentication Dial In User Service) -- A protocol
by which users can have access to secure networks through a centrally
managed server. RADIUS provides authentication for a variety of
services, such as login, dialback, SLIP, and PPP.
In a RADIUS query, the MAX provides a user ID and
password to the server. The server sends back a complete profile,
which specifies routing, packet filtering, destination-specific
static routes, and usage restrictions specific to the user. In
addition, the MAX can use the data in the RADIUS database to create
and advertise static routes and to place outbound calls.
The communications channel between a RADIUS client
and server is provided by UDP/IP, with messages acknowledged.
The primary advantage in using RADIUS to authenticate incoming
calls is that you can maintain all user information offline on
a separate UNIX-based server. You store virtually all Connection
Profile information on the RADIUS server in a flat ASCII database.
This server can accept authentication requests from many machines,
which makes swapping out one dial-in network server for another
much easier. (For more information, refer to RFC 2058 and 2059.)
RARP --
Reverse Address Resolution Protocol
RBOC --
Regional Bell Operating Company
RDP --
Reliable Data Protocol
redundancy
--
There are no perfect methods of transmitting signals--each one has inherent error rates, and all physical media is subject to damage. To safeguard against line and equipment failure during a transmission, a second, redundant line or unit can be active in the background to take over at any time. Network administrators always have a redundant (backup) module for multiplexers and other critical equipment.
Routers keep routing tables updated so that multiple paths to destinations in the network are always available.
Remote LAN Access
-- The process of allowing branch offices,
telecommuters, and traveling computer users to access the corporate
LAN backbone over dedicated or dialed, digital or analog lines.
remote management
-- A management feature that uses bandwidth
between sites over the management subchannel established by the
AIM (Ascend Inverse Multiplexing) protocol. Any Ascend unit can
control, configure, and obtain statistical and diagnostic information
about any other Ascend unit; multi-level security assures that
unauthorized personnel do not have access to remote management
functions.
REN
--
Ringer Equivalency Number. The sum total of the ringer equivalency numbers of phone equipment attached to a Pipeline cannot exceed 3. Voltage on board the Pipeline is the current used to make the attached devices ring. If too many devices are daisy chained together, or the sum of the REN of the equipment attached to the Pipeline exceeds 3, the Pipeline won't be able to supply enough voltage to make the units ring. REN value is usually printed on the bottom of a unit, and it is listed in the unit's manual.
RFC (Request For Comments)
-- The document series, begun in 1969, which
describes the Internet suite of protocols and related experiments.
Not all (in fact very few) RFCs describe Internet standards, but
all Internet standards are written up as RFCs. The RFC series
of documents is unusual in that the proposed protocols are forwarded
by the Internet research and development community, acting on
their own behalf, as opposed to the formally reviewed and standardized
protocols that are promoted by organizations such as CCITT and
ANSI. A complete list of RFCs can be found at http://www.internic.net/rfc/.
RI --
Ring Indicate
RIP (Routing Information Protocol)
-- Routing information protocol teaches routers
on a wide area network which routers have access to which addresses.
This information is kept in a routing table on each router. As
routers communicate with each other, they all update their routing
tables to include each others' routing table information. In a
large network environment, this exchange of information can keep
the network connections up unnecessarily, and can result in very
large routing tables on each router. You can apply a call filter
to ignore RIP updates. You can also control how route information
is propagated.
Router
-- An interconnection device that can connect
individual LANs. Unlike bridges, which logically connect at OSI
layer 2, routers provide logical paths at OSI layer 3. Like bridges,
remote sites can be connected using routers over dedicated or
switched lines to create WANs.
Routing
-- A device or setup that finds the best route
between any two networks, even if there are several networks to
traverse. (Contrast with bridge).
routing table
-- A list of destinations known to the router.
Routing tables are built and used based on three protocols:
- RIP - which continuously broadcasts routing updates
every 30 seconds
- ICMP - which can dynamically redirect packets
to a more efficient route
- ARP - which enables the Pipeline to respond to
address queries with its own physical address
RPC --
Remote Procedure Call
RPM --
Remote Port Module
RS-# --
Recommended Service #
RS-232
-- A set of EIA standards specifying various
electrical and mechanical characteristics for interfaces between
DTE and DCE data communications devices. The standard applies
to both synchronous and asynchronous binary data transmission
at rates below 64 kbit/s.
RSVP --
Reservation Protocol
RTS --
Request To Send
Rubber Bandwidth
-- A term used to describe a communications
channel whose bandwidth can be increased or decreased without
terminating and re-establishing the channel. Typically used with
inverse multiplexing.
RVD --
MIT Remote Virtual Disk Protocol
S interface
-- See S/T interface.
S/T interface
-- n. The electrical interface between a network
terminator (NT1) device and one or more ISDN communications devices
that do not contain their own NT1s.
S/T-interface
-- adj. Specifies an ISDN communications device
that connects to an external network terminator (NT1).
SAM (Secure Access Manager)
-- Secure Access Manager gives network administrators
granular control over the security functions of the entire network
directly from the central site. Through this Windows-based application,
network administrators can configure the Secure Access Firewall(s)
off-line and download the configuration to remote locations. The
menu-driven program enables network administrators to easily configure
the firewall on the network.
SAP --
Service Access Point
SAP filters
-- See NetWare call filters.
SDRP --
Source Demand Routing Protocol
Secure Access Firewalls
-- Secure Access Firewall is a software option
for Ascend units that offers a fully integrated firewall security
for remote networking. It uses state-of-the-art dynamic firewall
technology to deliver a comprehensive security solution for the
corporate LAN, remote office LAN and telecommuter's LAN that stops
intruders from breaking and entering into networks. Securing the
perimeter of the local network where it meets the Internet sets
the stage for using the Internet for Intranet applications.
Secure ID
-- A proprietary brand of security card (about
the size of a credit card) that generates a code based on the
user's ID, password, and information in the card. When the user
attempts to log on to a secure network, a code is requested that
must have been generated within the previous 60 seconds. The server
interprets the code, and if it is found to be genuine, the user
is granted access.
security cards
-- See Secure ID.
SEP --
Sequential Exchange Protocol
serial communication
-- Communication through the serial port of
your computer. For Windows 3.1, the maximum speed of the serial
port is 19,200. For Windows 95, the COM port limit on the settings
drop-down list is 921,600. These limitations are subject to change
as development of a faster serial bus design is implemented.
serial host
-- A device, such as a videoconferencing codec,
that is connected to a serial host port communicating over a point-to-point
link. To a serial host, the MAX appears to be a cable or DCE (Data
Communications Equipment).
serial host port
-- The V.35, RS-499, or X.21 port on the MAX.
serial host port module
-- A module on the MAX that connects to a
serial host through its serial host port.
session
-- The state a connection reaches when both
parties can communicate with each other.
signaling types
-- The sending device and the receiving device
must send signals in order to synchronize their clocks and determine
where one block of data ends and the next begins. Services
use signaling types to maintain synchronization and transfer
data effectively. Signals are either analog or digital. In-band
signaling is used by POTS, where all of the information about
the beginning and end of a call is carried on a single line. ISDN
BRI uses two B channels to carry data and a D channel to carry
signaling data.
SIP --
Simple Internet Protocol
SLIP (Serial Line IP)
-- A protocol that enables your computer to
send and receive IP packets over a serial link.
SMDS --
Switched Multimegabit Data Service. A packet-based
network service allowing the creation of high-speed data networks
(up to 45 Mbit/s). Now in the testing and initial implementation
phases.
SMTP --
Simple Mail Transfer Protocol
SNAP --
SubNetwork Access Protocol
SNMP (Simple Network Management
Protocol) -- A standard
way for computers to share networking information. -- In
SNMP, two types of communicating devices exist: agents and managers.
An agent provides networking information to a manager application
running on another computer. The agents and managers share a database
of information, called the Management Information Base (MIB).
An agent can use a message called a traps-PDU to send unsolicited
information to the manager.
The MAX supports
SNMP MIB II, T1 MIB, and Ascend Enterprise MIBs. You can therefore
manage the MAX from a central SNMP manager, such as SunNet Manager
or HP Open View. Because the WAN interface is integrated
into the MAX, you can manage it using the SNMP T1 MIB and Ascend
Enterprise MIB. Most other kinds of WAN interfaces, such as channel
banks, T1 muxes, and CSU/DSUs, cannot be incorporated into SNMP.
The MAX can send alarms, call detail reporting, and other management
information to an SNMP manager without being polled.
SNMP security is implemented using the community
name sent with each request. Ascend supports two community names,
one with read-only access, and the other with read/write access,
to the MIB.
socket
--
A TCP/IP interface that allows for a two-way link between two systems, letting applications run over a connection-less network. A socket is one end of a process that the application is using to communicate, and is defined by two addresses: the IP address of the host computer; and the port address of the application or process running on the host.
software compression
-- Software compression removes waste and
redundancy in a data file in order to save space and enable faster
throughput. The results of compression depend on the content of
each file being compressed: some contain a lot of waste, some
contain almost none.
SPID (Service Profile Identifier)
-- Service Profile Identifier. Your ISDN service
provider (telephone company) uses this number at the Central Office
switch to identify services on your ISDN line. This number is
derived from a telephone number.
Stacks
--
A stack is group of MAX units with a single stack name, acting as a single, logical unit. Stacks allow incoming (only) MP or MP+ calls to span multiple MAX units on a single LAN. There is no master unit in a stack. A MAX can become a member of a stack or leave a stack at any time, and there is no requirement to join a stack.
MAX units in a stack find each other using an Ethernet multicast packet. Since multicast packets are unlikely to cross a router, and high traffic demands created by a MP and MP+ calls, all members of a stack must reside on the same physical LAN.
straight-through cable
-- A cable with wires that have terminating
ends with the same wire assignments.
SWIPE --
IP with Encryption
SVC
-- Switched Virtual Circuit. A path over a packet-switched network that appears to be a dedicated circuit, but in fact the connection only stays up as long as needed, and then ends. (Also see PVC.)
Switched-1536
-- A data service consisting of a single 1536
kbps circuit, called an H11 channel. The H11 channel is comprised
of all 24 channels on the line. You must use two T1 PRI lines
to access Switched-1536. One line carries the user data, and the
other line contains the D-channel. NFAS is required for this data
service because the D channel must be on a separate line. This
service is available over T1 PRI lines only. Switched-1536 is
also known as H11 data service.
Switched-384
-- A data service consisting of a single 384
kbps circuit, called an H0 channel. The H0 channel is comprised
of 6 B channels. This service is available over T1 PRI lines only.
Switched-384 is also known as H0 data service.
Switched-56
-- A data service consisting of a single 56
kbps channel. This service is available over any type of line.
It is the only service available to T1 access lines and Switched-56
lines.
Because Switched-56 was the first
available data service, both the service itself and the lines
that accessed it were called Switched-56. However, any type of
line can now access Switched-56 data service, and there are other
new services in addition to Switched-56.
Switched-56 line
-- A line that provides a single 56 kbps data
channel with inband signaling.
Switched-64
-- A data service consisting of a single 64
kbps channel. This service is available over T1 PRI and ISDN BRI
lines only.
symbolic name
-- A name used in place of an IP address.
A symbolic name consists of a user name and a domain name in the
format user name@domain name. The user name corresponds to the
host number in the IP address. The domain name corresponds to
the network number in the IP address. A symbolic name might be
steve@crocker.com or joanne@cal.edu.
synchronization
-- In serial data transmission, a method of
ensuring that the receiving end can recognize characters in the
order in which the transmitting end sent them, and can know where
one character ends and the next begins. Without synchronization,
the receiving end would perceive data simply as a series of binary
digits with no relation to one another. Synchronous communication
relies on a clocking mechanism to synchronize the signals between
the sending and receiving machines.
synchronous transmission
-- A transmission mode in which the data moves
in large blocks, called messages or frames. Both the sending device
and the receiving device must maintain synchronization in order
to determine where one block of data ends and the next begins.
Synchronization can take one of these forms:
Each
side can transmit a separate synchronizing signal, called a clock.
Each frame or message can contain synchronization
information.
In the latter method, each
block of data starts with one or more control characters, usually
eight bytes long, called a SYNC. The receiver interprets the SYNC
as a signal that it can start accepting data. Synchronous transmission
can be up to 20 percent faster than asynchronous transmission.
T1 access line
-- A 1.544 mbps T1 line that provides 24 56
kbps data channels and uses inband signaling. This type of line
can contain all switched channels, all nailed-up channels, or
a combination of switched and nailed-up channels. You can connect
this type of line to standard voice or Switched-56 data services.
Using a feature called Drop-and-Insert, the MAX can use a portion
of a T1 access line for data purposes and pass the remaining portion
of the line's bandwidth to a PBX for voice purposes.
T1 line
-- A line that consists of 24 64 kbps channels.
Two types of T1 lines are available: T1 access lines and T1 PRI
lines.
T1 PRI line
-- A T1 line that uses 23 B channels for user
data, and one 64 kbps D channel for ISDN D-channel signaling.
The B channels can be all switched, all nailed up, or a combination
of switched and nailed up. This type of PRI line is a standard
in North America, Japan, and Korea. PRI stands for Primary Rate
Interface. You can connect this type of line to standard voice,
or Switched-56, Switched-64, Switched-384, Switched-1536, and
MultiRate data services. Using a feature called PRI-to-TI conversion,
the MAX can share the bandwidth of a T1 PRI line with a PBX.
T3 --
A digital transmission link with a capacity of 45
Mbit/s, or 28 T1 lines.
TACACS (Terminal Access Concentrator
Access Control Server) -- A very simple
query/response protocol that enables the MAX to check a user's
password, and enable or prevent access. A TACACS server supports
only the basic password exchanges that PAP uses; it does not support
CHAP.
Tariff
-- Documents filed by a regulated telephone
company with a state public utility commission or the Federal
Communications Commission. Document details services, equipment,
and pricing publicly offered by the telephone company.
terminal adapter --
A device that allows analog voice and data devices to work through an ISDN connection. The terminal adapter is a protocol converter that adapts equipment not designed for ISDN, such as phones, faxes, and modems.
TCP --
Transmission Control Protocol
Transmission Control Protocol/Internet
Protocol -- A family
of protocols that defines the format of data packets sent across
a network, and is the communications standard for data transmission
between different platforms. The TCP/IP family consists of the
following protocols and services.
- Transport protocols - these protocols control
data transmission between computers:
- TCP (Transmission Control Protocol)
- UDP (User Datagram Protocol)
- Routing protocols - these protocols control addressing
and packet assembly, and determine the best route for a packet
to take to arrive at its destination:
- IP (Internet Protocol)
- ICMP (Internet Control Message Protocol)
- RIP (Routing Information Protocol)
- OSPF (Open Shortest Path First)
- Gateway protocols - these protocols enable networks
to share routing and status information:
- EGP (Exterior Gateway Protocol)
- GGP (Gateway-to-Gateway Protocol)
- IGP (Interior Gateway Protocol)
- Network address services and protocols - these
services and protocols handle the way that each computer on a
network is identified:
- DNS (Domain Name System)
- ARP (Address Resolution Protocol)
- RARP (Reverse Address Resolution Protocol)
- User services - these services provide applications
a computer can use:
- BOOTP (Boot Protocol)
- FTP (File Transfer Protocol)
- Telnet
- Miscellaneous services
- NFS (Network File System)
- NIS (Network Information Service)
- RPC (Remote Procedure Call)
- SMTP (Simple Mail Transfer Protocol)
- SNMP (Simple Network Management Protocol)
TDM
--
Time Division Multiplexer (or Time Division Multiplexing)
TE --
Terminal Equipment
Telecommuter
-- A work-at-home computer user who connects
to the corporate LAN backbone using remote access technologies
(for example, using a modem over analog lines, ISDN Terminal Adapter
(TA) or ISDN router over ISDN lines, or CSU/DSU over Switched
56 lines).
Telnet
-- Terminal-to-remote host protocol developed
for ARPAnet. It is the TCP/IP protocol governing the exchange
of character-oriented terminal data. This protocol is used to
link two computers in order to provide a terminal connection to
the remote machine.
Instead of dialing
into the computer, you connect to it over the Internet using Telnet.
When you issue a Telnet session, you connect to the Telnet host
and log in. The connection enables you to work with the remote
machine as though you were a terminal connected to it.
If your MAX has an Ethernet card installed, you
can remotely manage it by establishing a Telnet session to the
remote unit from any Telnet workstation on the network and viewing
the MAX interface on a Telnet VT-100 window. All Pipeline units
except for the Pipeline 25 also support Telnet.
An
IP host can use Telnet to emulate a terminal. When you use the
MAX to initiate a terminal server session over Telnet or through
the local Control/Console port, the session has a subset of the
features available to a terminal server session over an asynchronous
WAN link.
terminal
-- A computer that does not have its own processor
and that must connect to a terminal server in asynchronous mode
in order to use its CPU. VT100, ANSI, and TTY are all types of
terminals.
terminal emulator
-- A program that makes your computer look
like a terminal so that you can connect to a terminal server.
Your computer acts like a terminal during the connection; all
processing is taking place remotely. A terminal emulator is also
called a terminal emulation program.
terminal server
-- A terminal server is a computing device
to which a terminal can connect over a LAN or WAN link. A terminal
communicates with the terminal server over an asynchronous serial
port (typically an RS-232 port) through a modem. A terminal converts
the data it receives from the terminal server into a display and
does no further processing of the data. A terminal also converts
the operator's keystrokes into data for transmission to the terminal
server.
terminal server session
-- An end-to-end connection between a terminal
and a terminal server. Usually, the terminal server session begins
when the call goes on line and ends when the call disconnects.
A terminal server session can be either local
or remote:
A local terminal server session
takes place when a terminal (or a computer emulating a terminal)
is connected to the Ascend unit's Control port, or when you open
a Telnet connection to the Ascend unit from an IP host.
In either case, you select the TermServ command from
the Sys Diag menu and press Enter to begin the terminal server
session. A local terminal server session has access to only a
subset of the commands available to a remote terminal server session.
A remote terminal server session takes place through
a digital modem or through a V.110 or V.120 connection to the
MAX.
A digital modem is a device that can
communicate over a digital line (such as a T1 PRI line) with a
station using a modem connected to an analog line. When you access
a terminal server through a digital modem, V.110, or V.120 connection,
the remote terminal server session begins immediately; you need
not enter the TermServ command.
Using an
integrated digital modem, the MAX allows a user to set up a remote
terminal server session at raw data rates of up to 28,8 kbps,
not including data compression. The MAX supports all the common
capabilities of standard terminal servers, including Telnet, Domain
Name Services (DNS), login and password control, call detail reporting,
and authentication services.
Thick Ethernet
-- A term that describes a type of Ethernet
cable. Thick Ethernet, or thicknet, is .4" diameter coaxial
cable for Ethernet networks.
Thin Ethernet
-- A term that describes a type of Ethernet
cable. Thin Ethernet, or thinnet, is .2" diameter coaxial
cable for Ethernet networks.
U interface
-- n. The electrical interface between an ISDN
telephone line and a network terminator (NT1) device.
U-interface
-- adj. Specifies an ISDN communications device
that connects directly to an ISDN telephone line. A U-interface
device contains its own network terminator (NT1).
UDP --
User Datagram Protocol
UTP --
Unshielded Twisted Pair
UTP cable
-- Unshielded Twisted Pair cable. Two paired
wires with wire twisted two or more times per inch to help cancel
out noise.
V.120
--
V.120 is a standard for encapsulating asynchronous data communication into ISDN data streams, which are synchronous. Two computers can communicate over an ISDN connection, using their standard, asynchronous-only COM ports and a V.120 adapter, which can be connected externally or internally.
Videoconferencing
-- The use of digital video transmission systems
to communicate between sites using video and voice. Digital video
transmission systems typically consist of camera, codec (coder-decoder),
network access equipment, network, and audio system.
VT-100
-- An ASCII character data terminal, consisting
of screen and keyboard. Manufactured by Digital Equipment Corporation
(DEC), the VT-100 has become an industry standard data terminal.
VT-100 emulation software allows a standard PC to act as a VT-100
terminal.
WAN --
Wide Area Network
Watchdog Spoofing
-- NetWare servers send 'session keep alive'
packets to clients who must return the packet to keep a session
active. Ascend units can reply to NetWare Core Protocol (NCP)
watchdog packets on behalf of clients on the other side of a bridge,
causing the server to sense that the link is still active. Effectively
imitating a return 'session keep alive' packet is called watchdog
spoofing.
Wide Area Network
-- A data network typically extending a LAN
outside a building or beyond a campus, over IXC or LEC lines to
link to other LANs at remote sites. Typically created by using
bridges or routers to connect geographically separated LANs.
WINS (Windows Internet Name Service)
-- Windows Internet Name Service (WINS) is
a Microsoft product that manages the mapping between resource
names (in the form of easy-to-remember nicknames) and IP addresses.
The DNS service used on the Internet cannot map between IP addresses
and local resource names dynamically. However, through dynamic
database updates, WINS lets users access network resources via
more user-friendly names instead of IP addresses.
WSN --
Wang Span Network
X.21 --
A set of CCITT specifications for an interface between
DTE and DCE for synchronous operation on public data networks.
Includes connector, electrical, and dialing specifications.
XNS IDP
-- Xerox Networking System Internetwork
Datagram Protocol