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availability
The property of an Internet service to be available to end client
without interruptions for long periods of time.
cache
A buffer that stores the most frequently used data, designed to
speed up subsequent access to it.
configuration
In SysMaster, a compilation of logically grouped SysMaster parameters
and objects, that are stored separately and define the all or a
part of the aspects of SysMaster operation. The action of SysMaster
depends on all configurations that are activated at a given time.
console
The operator's station of a server, network devices and mainframe
computers.
client
A computer or computer process that requests a service from another
computer system or process. For example, a web browser requesting
HTML documents from a web server.
cluster
A group of servers that are used for the same purpose and are identified
by a single hostname.
DNS
Domain Name System.
external interface
SysMaster network interface that is used for connection to the external
network.
external network
A network connected to the Internet.
firewall
A network device or a program running on a server, that filters
network traffic implementing security rules and restrictions.
FTP
(File Transfer Protocol) An application protocol used for transferring
files to and from network computers. FTP requires a user ID and
sometimes a password to allow access to files on a remote host system.
gateway
A device that interconnects two computer networks with different
architectures.(see also router)
geographic loadbalancing
Distributing requests across servers in different physical locations.
hash table
In SysMaster, a table containing the information of all current
connections, that is addressed by a special key which provides rapid
access to that information.
host
A computer, connected to a network, that provides an access point
to that network. A host can be a client, a server, or both simultaneously.
host name
The symbolic name assigned to a host. Host names are resolved to
IP addresses through a domain name server.
HTTP
(Hypertext Transfer Protocol) The protocol used to transfer
and display hypertext documents.
internal address
The IP address of the SysMaster device on the internal network.
internal interface
The SysMaster’s network interface that is used to connect to
the internal network.
internal network
The subnet to which the back-end server machines are connected.
Intranet
A secure, private network that integrates Internet standards and
applications (such as Web browsers) with an organization’s
existing computer networking infrastructure.
IP Internet Protocol
A connectionless protocol that routes data through a network or
interconnected networks. IP acts as an intermediary between the
higher protocol layers and the physical layer.
LAN Local Area Network
A computer network of devices connected within a limited geographical
area for communication and which can be connected to a larger network.
loadbalancing
Distributing incoming network traffic among servers, routers or
firewalls.
local management
Performing various configuration and administration tasks from the
console interface of the SysMaster (or a server). (See also remote
management)
loopback alias
An alternative IP address associated with the loopback interface.
loopback interface
An interface that bypasses unnecessary communications functions
when the information is addressed to an entity within the same system.
MAC address
The unique hardware address of network devices.
name server
A server that stores information about the domain name space.
NAT
Network Address Translation.
netbits
the number of bits that are used from an IP address to identify
the host.(See also netmask)
packet
A unit of data that is routed between a source and a destination
on a network.
packet forwarding method
The way a network packet is transported between the source and destination.
In the case of SysMaster 5000, between the SysMaster device and
the real servers.
persistence
A feature of SysMaster 5000 that allows all connections of a client
to be directed to one and the same real service for a specified
period of time.
persistency time
The time for which subsequent client request are directed to the
same real service. (See also sticky time)
ping
A program used to test reachability of destinations by sending them
one, or repeated echo requests and waiting for replies.
port
A number that identifies a logical communication channel or endpoint.
Web servers use port 80 by default.
primary
In redundant configurations, the SysMaster that starts out as the
machine actively routing packets. Its partner, the backup machine,
monitors the status of the primary machine and takes over if necessary.
See also backup, high availability.
protocol
A set of formal rules describing how to transmit data across a transport
media. Protocols can determine low-level details of machine-to-machine
interfaces, such as the order in which bits from a byte are sent;
they can also determine high-level exchanges between application
programs, such as file transfer.
physical server
A machine located on the internal network that provides services
on specific IP addresses and ports. (See also real server)
real server
A server from a cluster providing one or a set of the cluster services.
real service
The service or program running on a cluster server, that actually
processes client requests for a virtual service.
redirection
In SysMaster, forwarding the packets of network connection to the
cluster servers for processing.
redundancy
A SysMaster feature that allows one SysMaster to take over the function
of another, should that device fails.
remote management
Performing configuration and administration tasks on a server or
SysMaster device from a different machine using a Telnet connection
or through the SysMaster web interface.
reserved network
A network consisting of IP addresses that are not registered and
cannot be made visible outside of the internal network.
router
A network device that forwards packets between networks. The forwarding
decision is based on network layer information and routing tables,
often constructed by routing protocols.
scalablility
The capability of a system to adapt easily to a greater or lesser
workload. For example, a scalable system can efficiently adapt to
work with larger or smaller networks performing tasks of varying
complexity.
scheduling
Indicates the loadbalancing method used for distributing incoming
traffic among the real services, e.g. round robin, weighted round
robin, least connections.
server
A computer that provides shared services to other computers over
a network; for example, a file server, a web server, or a mail server.
server address
The IP address of a server that identifies it on the network. Multiple
IP addresses can be aliased to a one physical server.
server weight
A value that indicates the relative proportion of connection requests
that a particular back-end server will receive.
SSL
Secure Sockets Layer A protocol developed by Netscape Communications
Corp. that allows the client to authenticate the server and all
data and requests to be encrypted.
sticky time
The interval for which all consecutive connections from a client
are directed to the same real service. The sticky time starts to
flow from closing of one connection and is reset at the the opening
of a new connection. After the sticky time, the client may be sent
to any server from the cluster.
subnet mask
A 32–bit mask used to identify the bits in an IP address that
correspond to the network address and subnet portions of the address.
TCP
Transmission Control Protocol. A communications protocol used on
the Internet. TCP provides reliable host-to-host process-to-process
connections. It uses IP as the underlying protocol.
TCP/IP
Transmission Control Protocol/Internet Protocol. A suite of protocols
designed to allow communication between networks regardless of the
communication technologies used in each network.
Telnet
Terminal emulation protocol, a TCP/IP application protocol for remote
connection service. Telnet allows a user at one site to gain access
to a remote host as if the user’s workstation were connected
directly to that remote host.
UDP
User Datagram Protocol. Internet protocols that provides simple,
connectionless, but unreliable datagram service. It enables an application
program or a process to send a datagram to another application program
or process, but the delivery of the data packet is not guaranteed.
UDP uses the Internet Protocol (IP) to deliver datagrams.
virtual service
An Internet service that is managed by SysMaster 5000 by distributing
web traffic addressed for it among a cluster of real services. The
client sees only the virtual service address while the real services
can have their own IP addresses.
virtual service address (IP)
The IP address that is used for accessing a virtual service.
Web
The network of HTTP servers that contain programs and files, many
of them hypertext documents that contain links to other documents
on HTTP servers. Also Internet.
weight
A relative value that characterizes the processing capabilities
of a real server compared to the other servers in the cluster.
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