NonStop Server Interconnect
Product Description
Expand
Key features
- Single-system image
- Transparent operation in LAN and WAN environments
- Continuous availability and data integrity
- Robust network routing with automatic discovery of new nodes
- Online modular expansion
- Easy access to distributed system resources
- Security in networked applications
- Powerful network control facilities
- Flexible communications capabilities
Extending the benefits of NonStop servers
to networks
Tandem's Expand networking software extends the benefits of NonStop
servers--such as fault tolerance, modular expandability, and transparent
resource access--to networks of geographically distributed systems.
Through support of local and wide area network (LAN and WAN) configurations,
Expand lets users view an entire network of Tandem NonStop servers as a single
system. Up to 255 systems of 2 to 16 processors each can be connected--for a
maximum configuration of 4,080 processors.
Tandem's fault-tolerant architecture ensures that even in the event of a single
line or component failure, communications paths between physical systems are
continuously available. This enables applications to run reliably using data
and processes located anywhere in the network.
Expand architecture allows servers to be added or removed online. Data,
software, and application programs remain compatible, without the need for
reprogramming or reconfiguring the network.
In addition, Expand networking software allows applications requiring
distributed data to be run as though all data were physically stored in a
single location.
Single-system image
Simply by qualifying files, devices, and processes with a target system name,
applications can access remote or local resources using syntactically identical
file system calls. Applications need not be aware of the physical location of
any resource. This single-system image allows application resources to be
located and relocated within a network, while preserving your software
investment.
Transparent operation in LAN and WAN environments
Expand allows the transparent distribution of databases and applications over
WANs and industry-standard LANs.
Via the Tandem LAN Access Method (TLAM), Expand supports the transmission of
data over an Ethernet LAN. Expand functionality can coexist with other
protocols (including NETBIOS, TCP/IP, and OSI) operating over Ethernet.
In WAN configurations, Expand supports HDLC, extended HDLC for efficient
satellite transmissions, and full X.25 packet switching in adherence to both
the CCITT 1980 and 1984 standards. Expand is transparent to users in mixed WAN
and LAN configurations.
Continuous availability and data integrity
Like the NonStop servers it connects, Expand is designed for continuous
availability, even in the event of a single component or line failure. Expand
supports multiline paths between servers, ensuring availability while
increasing bandwidth and throughput.
Recovery from a line failure in a path is automatic, as is recovery from a
complete path failure between nodes. No operator intervention is required to
reconfigure the network--Expand reroutes the data transparently to the user.
Because Expand distributes network routing information to all systems, there is
no centralized routing function that can fail and paralyze the entire network.
Robust network routing with automatic discovery
of new nodes
Expand monitors network communications lines and automatically selects the path
with the least travel time between nodes (based on weighting factors).
Best-path routing assures that the most effective communications path is
selected.
Because the addition of a new line may generate a number of path changes,
Expand software updates the network routing table in each Tandem server to
assure that messages continue to be routed along the best path. The updating of
the routing table by Expand is done without network downtime or operator
intervention.
If a path fails, Expand automatically reroutes and retransmits (when
appropriate) the message using the next-best available path. This feature
provides an added measure of fault tolerance and assures that communications
line failures will not cause the loss or corruption of messages.
In an X.25 environment, Expand can establish and terminate switched virtual
circuits. It also supports X.25 permanent virtual circuits.
Online modular expansion
Individual Tandem servers within an Expand network may have different computing
requirements. Expand software allows users to place exactly the right amount of
computing power at each site. Servers can be added or removed without affecting
the rest of the network--and without reprogramming. Data, software, and
application programs remain compatible, and there is no need for time-consuming
and costly network reconfiguration.
As transmission requirements may also vary between nodes, lines can be added or
deleted to adjust bandwidth in economical increments. Transmission capacity is
matched to the requirements of the user.
Easy access to distributed system resources
As an extension of the Tandem NonStop Kernel, data in an Expand network can be
configured as a single, integrated database. The fact that data is
geographically distributed is transparent to the user, who can access any
resource (processors, files, or devices) in the network, regardless of its
physical location.
Programs developed for use on a single server are equally valid on multiple
servers. Nodes can be added or removed; communications paths can be changed;
and system and network loads can be redistributed dynamically online and
without changing application software.
Tandem provides industry leadership with Transaction Monitoring Facility (TMF)
software, which ensures database integrity, for both inquiry and updates,
across a network--even in the event of a line or node failure.
Security in networked applications
Expand uses the facilities of the NonStop Kernel for basic system protection.
Safeguard software extends the NonStop Kernel security features, allowing
administrators to implement a variety of security policies through the
following:
- Authentication, to verify the identity of system users
- Authorization, to control user access to system resources
- Auditing, to record specified activities on the system
Powerful network control facilities
Expand provides network monitoring programs that allow any server within a
network to act as a center for monitoring the network. These programs provide
the following:
- Logging and display of changes in network status as seen from the selected
system
- Logging and display of changes in processor status at remote systems
- Display of network traffic statistics
- Display of current paths to selected remote systems
Flexible communications capabilities
Expand supports a variety of communications interfaces, including leased line,
fiber optics, X.25 packet switching (permanent and switched virtual circuit
support, 1980 and 1984 versions), satellite-efficient protocols, and LAN (see
figure).
Expand networking software supports a number of communications interfaces,
including fiber optics, satellite, leased line, X.25 packet switching, and LAN.
Components of Expand
Expand software includes the following components that assist users in the
design and operation of an Expand network:
- The network control process (NCP) runs in each Tandem server in the
network. It establishes communications paths to other nodes, maintains routing
information, determines best-path routing to other nodes, and monitors and logs
changes in the status of the network.
- Network line handlers manage communications paths and implement a Tandem
defined end-to-end protocol. This protocol guarantees data integrity from
sender to receiver, regardless of the number of intervening nodes involved in
the transfer.
Specifications
System requirements
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Hardware | Any NonStop server |
| Software | Tandem NonStop Kernel, any supported software | | release |
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Ordering information
Product ID Description
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9057 | Expand networking system
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Tandem, Expand, NonStop, Safeguard, TMF, and the Tandem logo are trademarks of Tandem Computers Incorporated. All other brand and product names are trademarks or registered trademarks of their respective companies. Technical specifications and availability are subject to change without notice. |
| (c)1994 Tandem Computers Incorporated CD0194-0194
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