HP StorageWorks Enterprise File Services WAN Accelerator 3.0.4 deployment guide (AG421-96001, March 2007)

134 GLOSSARY
WAN Accelerator only optimizes access to data to which exclusive access is available
(in other words, when locks are granted). When an oplock is not available the HP EFS
WAN Accelerator does not perform application-level latency optimizations but still
performs Scalable Data Referencing and compression on the data as well as TCP
optimizations. Therefore, even without the benefits of latency optimization, HP EFS
WAN Accelerators may still increase WAN performance, but not as effectively as
when application optimizations are available.
OSPF. Open Shortest Path First. An interior gateway routing protocol developed for
IP networks based on the shortest path first or link-state algorithm. Routers use link-
state algorithms to send routing information to all nodes in an internetwork by
calculating the shortest path to each node based on a topography of the Internet
constructed by each node. Each router sends that portion of the routing table (keeps
track of routes to particular network destinations) that describes the state of its own
links. It also sends the complete routing structure (topography).
Packet. A unit of information transmitted, as a whole, from one device to another on
a network.
Probe. A small utility program that is used to investigate, or test, the status of a system,
network or Web site.
Policy. Routing and Quality of Service (QoS) scheme that forwards data packets to
network interfaces based on user-configured parameters.
Port. A pathway into and out of the computer or a network device such as a hub,
switch, or router. On network devices, the ports are for communications, typically
connecting Ethernet cables or other network devices.
Router. A device that forwards data packets from one LAN or WAN to another. Based
on routing tables and routing protocols, routers read the network address in each
transmitted frame and make a decision on how to send it based on the most expedient
route (traffic load, line costs, speed, bad lines, etc.). Routers work at Layer-3 in the
protocol stack, whereas bridges and switches work at the Layer-2.
SMB. Server Message Block. A message format used by DOS and Windows to share
files, directories and devices. There are also a number of products that use SMB to
enable file sharing among different operating system platforms. A product called
Samba, for example, enables UNIX and Windows machines to share directories and
files.
SNMP. Simple Network Management Protocol. A network protocol that provides a
way to monitor network devices, performance, and security and to manage
configurations and collect statistics.
Switch. A network device that filters and forwards frames based on the destination
address of each frame. The switch operates at Layer-2 (data link layer) of the Open
System Interconnection (OSI) model.
TCP. Transmission Control Protocol. The error correcting Transport layer (Layer-4) in
the TCP/IP protocol suite.
TCP/IP. Transmission Control Protocol/Internet Protocol. The protocol suite used in
the Internet, intranets, and extranets. TCP provides transport functions, which ensures