E1 or E-1
E1 or E-1 is the European/China format for digital signal transmission, while T1/DS1 is for the North America/Japan. E1 carries signals at 2 Mbps with 32 channels at 64Kbps each, where 30 DS0 channels for voice/data and 2 channels for signaling and controlling. For T1, it carries signals at 1.544 Mbps with 24 channels at DS0 64Kbps each. E1 and T1 lines may be interconnected for international use.
Standard Organization: ITU-T

E3 or E-3
E3 or E-3 is the European/China format for digital signal transmission, while T3/DS3 is for the North America/Japan. E3 carries data at a rate of 34.368 Mbps. E3 can carry 16 E1 channels. E3 and T3 lines may be interconnected for international use.
Standard Organization: ITU-T

EAP: PPP Extensible Authentication Protocol
The PPP Extensible Authentication Protocol (EAP) is for PPP authentication. EAP supports multiple authentication mechanisms. EAP does not select a specific authentication mechanism at Link Control Phase, but rather postpones this until the Authentication Phase. This allows the authenticator to request more information before determining the specific authentication mechanism. This also permits the use of a "back-end" server which actually implements the various mechanisms while the PPP authenticator merely passes through the authentication exchange.
Standard Organization: IETF
Reference Document: RFC 2284

EAP-TLS: Extensible Authentication Protocol - Transport Layer Security
Extensible Authentication Protocol - Transport Layer Security(EAP-TLS) is an encrypted authentication scheme based on Extensible Authentication Protocol (EAP). EAP-TLS was created by Microsoft and accepted by the IETF.
Standard Organization: IETF
Reference Document: RFC 2716

EAP-TTLS: Extensible Authentication Protocol - Tunneled Transport Layer Security
Extensible Authentication Protocol - Tunneled Transport Layer Security (EAP-TTLS) is an encrypted authentication scheme based on Extensible Authentication Protocol (EAP) and easier to manage than Extensible Authentication Protocol - Transport Layer Security (EAP-TLS). EAP-TTLS is a proprietary protocol which was developed by Funk Software and Certicom, and is supported by Agere Systems, Proxim, and Avaya.
Standard Organization: Funk Software

EAPOL: EAP over LAN
EAP over LAN (EAPOL), defined in the IEEE 802.1X, offers an effective framework for authenticating and controlling user traffic to a protected network, as well as dynamically varying encryption keys. EAPOL is a standard for passing Extensible Authentication Protocol (EAP) over a wired or wireless LAN. In the wireless environment, 802.1X also describes a way for the access point and the wireless user to share and change encryption keys, and adds some messages which help smooth operations over wireless. The key change messages help solve the major security vulnerability in 802.11, the management of WEP keys. With 802.1X, WEP is brought up to an acceptable level of security for most companies.
Standard Organization: IEEE

ECHO: Echo Protocol
Echo Protocol (ECHO) is defined in RFC 862 for testing and measurement purposes in an IP network. A host may connect to a server that supports the ECHO protocol, on either TCP or UDP port 7. The server then sends back any data it receives. Current testing and measurement of IP networks is more commonly done with ping and t raceroute defined in the ICMP.
Standard Organization: IETF

ECP: Encryption Control Protocol
Encryption Control Protocol (ECP), a protocol in the PPP suite, can be used to ensure that only authorized devices can establish a PPP connection. ECP is responsible for negotiating and managing the use of encryption on a PPP link.
Standard Organization: IETF
Reference Document: RFC 1968

EGP: Exterior Gateway Protocol
Exterior Gateway Protocol (EGP) is for exchanging routing information between two neighbor gateway hosts in a network of autonomous systems. EGP is commonly used between hosts on the Internet to exchange routing table information. The protocol is based on periodic polling using Hello/I-Heard-You (I-H-U) message exchanges to monitor neighbor reachability and Poll commands to solicit Update responses.
Standard Organization: IETF
Reference Document: RFC 904

EIGRP: Enhanced Interior Gateway Routing Protocol
Enhanced Interior Gateway Routing Protocol (EIGRP) is an enhanced version of IGRP. IGRP is Cisco's Interior Gateway Routing Protocol used in TCP/IP and OSI internets. It is regarded as an interior gateway protocol (IGP) but has also been used extensively as an exterior gateway protocol for inter-domain routing.
Standard Organization: Cisco

ELAP: EtherTalk Link Access Protocol
EtherTalk Link Access Protocol (ELAP) is a link-access protocol used in an AppleTalk over Ethernet network. ELAP is built on top of the standard Ethernet data link layer.

ENUM: E164 NUmber Mapping
Electronic Numbering (ENUM or Enum), also refered to as "E164 NUmber Mapping", is a suite of protocols to unify the telephone system with the Internet by using E.164 addresses with Dynamic Delegation Discovery System (DDDS) and Domain Name System (DNS). ENUM is a standard adopted by the Internet Engineering Task Force (IETF) that uses the domain name system (DNS) to map telephone numbers to Web addresses or uniform resource locators (URL). The goal of the ENUM standard is to provide a single number to replace the multiple numbers and addresses for an individual's home phone, business phone, fax, cell phone, and e-mail.
Standard Organization: IETF
Reference Document: RFC 3761

ENUM: Electronic Numbering
Electronic Numbering (ENUM or Enum), also refers to "E164 NUmber Mapping", is a suite of protocols to unify the telephone system with the Internet by using E.164 addresses with DDDS and DNS. ENUM is a standard adopted by the Internet Engineering Task Force (IETF) that uses the domain name system (DNS) to map telephone numbers to Web addresses or uniform resource locators (URL). The goal of the ENUM standard is to provide a single number to replace the multiple numbers and addresses for an individual's home phone, business phone, fax, cell phone, and e-mail.
Standard Organization: IETF
Reference Document: RFC 3761

EoS: Ethernet over SONET/SDH
Ethernet over SONET/SDH (EoS) refers to a group of industry standard specifications for optimal transport of Ethernet through SONET/SDH, because Ethernet is not directly supported over the SONET/SDH network traditionally. Basically, EoS capability turns the Sonet/SDH MAN/WAN infrastructure backbone into a transparent Ethernet segment for attached servers and clients.
Standard Organization: ITU-T

EPON: Ethernet Passive Optical Network
Ethernet Passive Optical Network (EPON), defined by IEEE 802.3ah, is a point to multipoint (Pt-MPt) network topology implemented with passive optical splitters, along with optical fiber PMDs that support this topology. EPON is based upon a mechanism named MPCP (Multi-Point Control Protocol), which uses messages, state machines, and timers, to control access to a P2MP topology. Each ONU in the P2MP topology contains an instance of the MPCP protocol, which communicates with an instance of MPCP in the OLT. On the basis of the EPON/MPCP protocol lies the P2P Emulation Sublayer, which makes an underlying P2MP network appear as a collection of point-to-point links to the higher protocol layers (at and above the MAC Client). It achieves this by prepending a Logical Link Identification (LLID) to the beginning of each packet, replacing two octets of the preamble. In addition, a mechanism for network Operations, Administration and Maintenance (OAM) is included to facilitate network operation and troubleshooting.
Standard Organization: IEEE

ES-IS: End System to Intermediate System Routing Exchange Protocol
End System to Intermediate System Routing Exchange Protocol (ES-IS), developed by ISO, permits End Systems and Intermediate Systems to exchange configuration and routing information to facilitate the operation of the routing and relaying functions of the Network Layer in the ISO network environment. In an ISO network, there are End Systems, Intermediate Systems, Areas and Domains. End systems are user devices. Intermediate systems are routers. Routers are organized into local groups called 'areas' and several areas are grouped together into a 'domain'.
Standard Organization: ISO
Reference Document: ISO 8473

ESMTP: Extended Simple Mail Transfer Protocol
Extended Simple Mail Transfer Protocol (ESMTP) is the extended version of the original Simple Mail Transfer Protocol (SMTP), which includes additional functionality, such as delivery notification and session delivery. All the features of ESMTP are included in the latest version of SMTP as defined in RFC 2821 and the ESMTP is no longer necessary.
Standard Organization: IETF
Reference Document: RFC 2821

ESP: Encapsulating Security Payload
Encapsulating Security Payload (ESP), a key protocol in the IPsec (Internet Security) architecture, is designed to provide a mix of security services in IPv4 and IPv6. The IP Encapsulating Security Payload (ESP) seeks to provide confidentiality and integrity by encrypting data to be protected and by placing the encrypted data in the data portion of the IP ESP. Depending on the user's security requirements, this mechanism may be used to encrypt either a transport-layer segment (e.g., TCP, UDP, ICMP, IGMP) or an entire IP datagram. Encapsulating the protected data is necessary to provide confidentiality for the entire original datagram.
Standard Organization: IETF
Reference Document: RFC 2406

Ethernet
Ethernet protocols refer to the family of local area networks (LAN) covered by a group of IEEE 802.3 standards. In the Ethernet standard, there are two modes of operation: half-duplex and full-duplex. In the half-duplex mode, data are transmitted using the popular Carrier-Sense Multiple Access/Collision Detection (CSMA/C D) protocol on a shared medium. The main disadvantages of the half-duplex are the efficiency and distance limitation, in which the link distance is limited by the minimum MAC frame size. This restriction reduces the efficiency drastically for high-rate transmission. Therefore, the carrier extension technique is used to ensure the minimum frame size of 512 bytes in Gigabit Ethernet to achieve a reasonable link distance.
Standard Organization: IEEE
Reference Document: IEEE 802.3

EtherTalk
EtherTalk, full named as EtherTalk Link Access Protocol (ELAP), places AppleTalk's DDP formatted packets in Ethernet frames. EtherTalk enables the implementation of AppleTalk using Ethernet as a delivery system.