H

Host Attach. In ExtremeXOS software, HA is part of ESRP that allows you to connect active hosts directly to an ESRP switch; it allows configured ports to continue Layer 2 forwarding regardless of their ESRP status.

This is the communication mode in which a device can either send or receive data, but not simultaneously. (Devices at 1 Gbps or higher do not run in half-duplex mode; they run only in full-duplex mode.)

This is control information (such as originating and destination stations, priority, error checking, and so forth) added in front of the data when encapsulating the data for network transmission.

A UDP data packet used to monitor a data connection, polling to see if the connection is still alive.
 In general terms, a heartbeat is a signal emitted at regular intervals by software to demonstrate that it is still alive. In networking, a heartbeat is the signal emitted by a Level 2 Ethernet transceiver at the end of every packet to show that the collision-detection circuit is still connected.

In the Extreme Networks implementation on modular switches and SummitStacks, hitless failover means that designated configurations survive a change of primacy between the two MSMs (modular switchtes) or master/backup nodes (SummitStacks) with all details intact. Thus, those features run seamlessly during and after control of the system changes from one MSM or node to another.

1. A computer (usually containing data) that is accessed by a user working on a remote terminal, connected by modems and telephone lines.
2. A computer that is connected to a TCP/IP network, including the Internet. Each host has a unique IP address.

Hypertext Transfer Protocol is the set of rules for transferring files (text, graphic images, sound, video, and other multimedia files) on the World Wide Web. A Web browser makes use of HTTP. HTTP is an application protocol that runs on top of the TCP/IP suite of protocols. (RFC 2616: Hypertext Transfer Protocol -- HTTP/1.1)

Hypertext Transfer Protocol over Secure Socket Layer, or HTTP over SSL, is a web protocol that encrypts and decrypts user page requests as well as the pages that are returned by the Web server. HTTPS uses Secure Socket Layer (SSL) as a sublayer under its regular HTTP application layering. (HTTPS uses port 443 instead of HTTP port 80 in its interactions with the lower layer, TCP/IP.) SSL uses a 40-bit key size for the RC4 stream encryption algorithm, which is considered an adequate degree of encryption for commercial exchange.