Secure Shell, sometimes known as Secure Socket Shell, is a UNIX-based command interface and
protocol of securely gaining access to a remote computer. With SSH commands, both ends of the
client/server connection are authenticated using a digital certificate, and passwords are protected by
being encrypted. At Extreme Networks, the SSH is a separate software module, which must be
downloaded separately. (SSH is bundled with SSL in the software module.)
SSID
The Service Set Identifier is a 32-character unique identifier attached to the header of packets sent over
a Wireless LAN that acts as a password when a wireless device tries to connect to the BSS (Basic
Service Set). Several BSSs can be joined together to form one logical WLAN (Wireless Local Area
Network) segment, referred to as an (ESS (Extended Service Set)). The SSID is used to identify the ESS.
In 802.11 networks, each AP (Access Point) advertises its presence several times per second by
broadcasting beacon frames that carry the ESS name (SSID). Stations discover APs by listening for
beacons, or by sending probe frames to search for an AP with a desired SSID. When the station locates
an appropriately-named access point, it sends an associate request frame containing the desired SSID.
The AP replies with an associate response frame, also containing the SSID.
Some APs can be configured to send a zero-length broadcast SSID in beacon frames instead of sending
their actual SSID. The AP must return its actual SSID in the probe response.
SSL
Secure Socket Layer is a protocol for transmitting private documents using the Internet. SSL works by
using a public key to encrypt data that is transferred over the SSL connection. SSL uses the public-and-
private key encryption system, which includes the use of a digital certificate. SSL is used for other
applications than SSH (Secure Shell), for example, OpenFlow.
STP
Spanning Tree Protocol, defined in IEEE 802.1d, used to eliminate redundant data paths and to increase
network eciency. STP allows a network to have a topology that contains physical loops; it operates in
bridges and switches. STP opens certain paths to create a tree topology, thereby preventing packets
from looping endlessly on the network. To establish path redundancy, STP creates a tree that spans all
of the switches in an extended network, forcing redundant paths into a standby, or blocked, state.
STP allows only one active path at a time between any two network devices (this prevents the loops)
but establishes the redundant links as a backup if the initial link should fail. If STP costs change, or if one
network segment in the STP becomes unreachable, the spanning tree algorithm reconfigures the STP
topology and re-establishes the link by activating the standby path.
STPD
Spanning Tree Domain is an STP (Spanning Tree Protocol) instance that contains one or more VLAN
(Virtual LAN)s. The switch can run multiple STPDs, and each STPD has its own root bridge and active
path. In the Extreme Networks implementation of STPD, each domain has a carrier VLAN (for carrying
STP information) and one or more protected VLANs (for carrying the data).
stub area
In OSPF (Open Shortest Path First), a stub area is connected to only one other area (which can be the
backbone area). External route information is not distributed to stub areas.
SVL
Glossary
ISW Series Managed Industrial Ethernet Switch Command Reference Guide 164
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