S

Source address. The SA is the IP or MAC address of the device issuing the packet.

Secure Copy Protocol. SCP2, part of SSH2, is used to transfer configuration and policy files.

Software-defined Networking. An approach to computer networking that seeks to manage network services through decoupling the system that makes decisions about where traffic is sent (control plane) from the underlying systems that forward traffic to the selected destination (data plan).

In EAPS, the secondary port is a port on the master node that is designated the secondary port to the ring. The transit node ignores the secondary port distinction as long as the node is configured as a transit node.

In Ethernet networks, a section of a network that is bounded by bridges, routers, or switches. Dividing a LAN segment into multiple smaller segments is one of the most common ways of increasing available bandwidth on the LAN.

A certificate identifying a server. When a client connects to the server, the server sends its certificate to the client and the client validates the certificate to trust the server.

sFlow allows you to monitor network traffic by statistically sampling the network packets and periodically gathering the statistics. The sFlow monitoring system consists of an sFlow agent (embedded in a switch, router, or stand-alone probe) and an external central data collector, or sFlow analyzer.

Small form-factor pluggable. These transceivers offer high speed and physical compactness.

This term refers to the data path for packets that must be processed by the switch CPU, whether these packets are generated by the CPU, removed from the network by the CPU, or simply forwarded by the CPU.

Service Location Protocol. A method of organizing and locating the resources (such as printers, disk drives, databases, e-mail directories, and schedulers) in a network.

Using SLP, networking applications can discover the existence, location and configuration of networked devices. 
With Service Location Protocol, client applications are 'User Agents' and services are advertised by 'Service Agents'. The User Agent issues a multicast 'Service Request' (SrvRqst) on behalf of the client application, specifying the services required. The User Agent will receive a Service Reply (SrvRply) specifying the location of all services in the network which satisfy the request. 
For larger networks, a third entity, called a 'Directory Agent', receives registrations from all available Service Agents. A User Agent sends a unicast request for services to a Directory Agent (if there is one) rather than to a Service Agent.
 (SLP version 2, RFC2608, updating RFC2165)

Single-mode fiber. SMF is a laser-driven optical fiber with a core diameter small enough to limit transmission to a single bound mode. SMF is commonly used in long distance transmission of more than three miles; it sends one transmission at a time.

Structure of Management Information. A hierarchical tree structure for information that underlies Management Information Bases (MIBs), and is used by the SNMP protocol. Defined in RFC 1155 and RFC 1442 (SNMPv2).

Switch Network Monitoring Management (MIB) system defined by the IETF document RFC 2613. SMON is a set of MIB extensions for RMON that allows monitoring of switching equipment from a SNMP Manager in greater detail.

Station Management. The object class in the 802.11 MIB that provides the necessary support at the station to manage the processes in the station such that the station may work cooperatively as a part of an IEEE 802.11 network. The four branches of the 802.11 MIB are:

• dot11smt—objects related to station management and local configuration
• dot11mac—objects that report/configure on the status of various MAC parameters
• dot11res—objects that describe available resources
• dot11phy—objects that report on various physical items

Simple Network Management Protocol. SNMP is a standard that uses a common software agent to remotely monitor and set network configuration and runtime parameters. SNMP operates in a multivendor environment, and the agent uses MIBs, which define what information is available from any manageable network device. You can also set traps using SNMP, which send notifications of network events to the system log.

Simple Network Time Protocol. SNTP is used to synchronize the system clocks throughout the network. An extension of the Network Time Protocol, SNTP can usually operate with a single server and allows for IPv6 addressing.

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.)

Service Set Identifier. 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 Basic Service Set (BSSs). Several BSSs can be joined together to form one logical WLAN segment, referred to as an extended service set (ESS). The SSID is used to identify the ESS. 


In 802.11 networks, each access point (AP) 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.

Secure Sockets Layer. SSL 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, for example, OpenFlow.

Hijacking a server‘s IP address or hostname so that requests to the server are redirected to another server. Certificate validation is used to detect and prevent this.

Use ESRP standard mode if your network contains switches running ExtremeWare and switches running ExtremeXOS, both participating in ESRP.

Spanning Tree Protocol. STP is a protocol, defined in IEEE 802.1d, used to eliminate redundant data paths and to increase network efficiency. 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.

Spanning Tree Domain. An STPD is an STP instance that contains one or more VLANs. 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).

The mode of operation for the STPD. The two modes of operation are:

• 802.1d—Compatible with legacy STP and other devices using the IEEE 802.1d standard.
• 802.1w—Compatible with Rapid Spanning Tree (RSTP).

In OSPF, 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.

See netmask.

Portions of networks that share the same common address format. A subnet in a TCP/IP network uses the same first three sets of numbers (such as 198.63.45.xxx), leaving the fourth set to identify devices on the subnet. A subnet can be used to increase the bandwidth on the network by breaking the network up into segments.

In EAPS, a superloop occurs if the common link between two EAPS domains goes down and the master nodes of both domains enter the failed state putting their respective secondary ports into the forwarding state. If there is a data VLAN spanning both EAPS domains, this action forms a loop between the EAPS domains.

SpectraLink Voice Protocol, a protocol developed by SpectraLink to be implemented on access points to facilitate voice prioritization over an 802.11 wireless LAN that will carry voice packets from SpectraLink wireless telephones.

A protocol used for the transmission of event notification messages across networks, originally developed on the University of California Berkeley Software Distribution (BSD) TCP/IP system implementations, and now embedded in many other operating systems and networked devices. A device generates a messages, a relay receives and forwards the messages, and a collector (a syslog server) receives the messages without relaying them. 
Syslog uses the user datagram protocol (UDP) as its underlying transport layer mechanism. The UDP port that has been assigned to syslog is 514. (RFC 3164)

The primary responsibility of the system health checker is to monitor and poll error registers. In addition, the system health checker can be enabled to periodically send diagnostic packets. System health check errors are reported to the syslog.