Ethernet at the Data Link Layer Ethernet provides services corresponding to Layers 1 and 2 of the OSI reference model, and IEEE 802.3 specifies the physical layer (Layer 1) and the channel-access portion of the Data Link (Layer 2). In addition, IEEE 802.3 does not define a logical link control protocol but does not specify several different physical layers, whereas Ethernet defines only one. Ethernet Addressing Every network device has a unique physical identity that is assigned by the manufacturing vendor is called MAC address or Ethernet address. The mac Read More

The Session Layer is Layer 5 of the OSI (Open Systems Interconnection) Model of computer networking. The Session Layer is directly after the Transport Layer and before the Presentation Layer, allowing it to interact with applications as well as network components. The Session Layer is responsible for opening, maintaining, and closing all sessions between multiple applications and/or devices. Because almost all network-related events involve the use of sessions, the Session Layer is used extremely often.   How The Session Layer Works The Session Layer is responsible for opening, maintaining, and Read More

H.323 is an ITU standard multimedia conferencing protocol, which includes voice, video, and data conferencing, for use over packet-switched networks. H.323 was the first standard for VoIP, but is being supplanted by SIP. H.323 defines five components of a multimedia network: Terminals Multipoint Control Units (MCUs) Gateways Gatekeeper Border Elements Terminals are telephone and PC equipment which connect end-users to the H.323 network. MCUs are responsible for managing conferences. MCU’s consist of a Multipoint Controller (MC) and an optional Multipoint Processor (MP). The MC manages signaling and the MP manages Read More

Wireless networks are those computer networks that use electromagnetic waves instead of wires in order to carry signals over the various parts of the network. Wireless networks which run over other wireless networks often utilize the lower layer networks to provide security and encryption. Stand-alone wireless networks either provide their own security and encryption features or rely upon VPNs (Virtual Private Networks) to provide those features. In many cases, multiple layers of security and encryption may be desirable. Need for Wireless Networks and their Benefits Wireless networks belong to the Read More

In the past, two main termination specifications were used. One was for UTP data cable infrastructure and the other for phone cable infrastructure. Today, structured cable systems are in use. 568A is one such standard. 568A is a standard for the pin arrangements of RJ-45 connectors on Unshielded Twisted Pair (UTP) wire. The cryptic number 568 refers to the order in which the individual wires inside a CAT 5 cable are terminated. The 568 standards were actually developed by the TIA (Telecommunications Industry Association) and the EIA (Electronics Industry Association) Read More

What is CDP? CDP is the Cisco Discovery Protocol. It is a Cisco Proprietary Protocol that discovers and shows information about directly connected Cisco devices. CDP works on layer two (Data Link layer) of the OSI Reference Model. Cisco Discovery Protocol (CDP) works only with the Cisco manageable devices such as Cisco Catalyst Switches and Cisco Routers and Access Server. It is a useful utility of Cisco IOS that runs on the routers with the Cisco IOS version 10.3 or later and Cisco switches and hubs. CDP is basically network Read More

A fiber optic connector (optical fiber connector) is a small glass or plastic device that is placed at the end of a fiber optic cable in order to allow light from the cable to enter another device. Fiber optic connectors are often spring-loaded and align the core of each fiber so that they are all directly touching the receiver. This allows light to be contained within the fiber optic cable rather than being let out into the air, in which case data would be lost. While fiber optic connectors are Read More

VRRP stands for Virtual Router Redundancy Protocol. The VRRP is a commonly used method to avoid network outages during important data transfers. Data transfer can be highly susceptible to failure when sent by a single router network. To combat this problem, VRRP creates a virtual connection between routers within the same network and ties them together. If the initial router used to send the data fails for any reason, another router automatically takes over the transfer. Is the VRRP a physical router? No. The VRRP is, as the name indicates, Read More

Reverse DNS is the process of using DNS to translate IP addresses to hostnames. It is the opposite of forward DNS, which is used to translate hostnames to IP addresses. Internet names are those used to refer to hosts on the Internet, such as www.byteguide.com and www.freebsd.org. IP addresses are the numbers that Internet routers use to move traffic across the Internet, such as 216.17.138.115 and 216.136.204.117. Reverse DNS Lookups One of the best ways to understand reverse DNS is to use the DNS testing tool, `nslookup` to do a Read More

Definitions Integrated Services Digital Network (ISDN): ISDN is a digital transmission system, which is used to transmit voice and data through copper telephone wires. In other words, it's a circuit-switched data transmission system that is used for voice and data transmission over the wire. Digital Subscriber Line (DSL): DSL is also a digital transmission system and utilizes already installed copper wires to send voice and data packets. Differences As far as the differences between ISDN and DSL transmission system are concerned, there are several differences one can find: Speed In Read More