The OSI Reference Model
No real world network operating systems conform exactly to the OSI model, but it is useful as a reference when describing existing systems. It is difficult to study network devices such as routers, switches, and gateways without using the model. More ...
DSL (Digital Subscriber Line)
DSL (Digital Subscriber Line) is a technology used to transmit digital data over telephone lines. DSL service can be transmitted simultaneously with voice band telephone service on the same line because DSL uses a much higher frequency that rides on top of the low 3400 Hz voiceband. More ...
Ports and Sockets
Data transmitted over the Internet carries a 32-bit IP address that identifies its destination computer and a 16-bit number that identifies a port on that computer. The combination of the IP address and the port number is called a socket. A pair of sockets, one on the sending computer and one on the receiving computer uniquely identifies a specific connection on the Internet. More ...
RADIUS Protocol
RADIUS (Remote Authentication Dial-In User Service) is an application layer protocol that provides centralized Authorization, Authentication, and Accounting management for users who connect and use a network service. More ...
The OSI Session Layer
The Session layer, layer seven of the OSI model, establishes, synchronizes, maintains and terminates sessions between computers on a network. It establishes a connection ID and authenticates security. More ...
IPv6 Dynamic Address Allocation
As with IPv4, IPv6 addresses can be statically assigned. However, when it comes to dynamic addressing, IPv6 has a different approach. IPv6 uses the ICMPv6 Router Advertisement message to suggest to devices how to obtain their IPv6 addressing information. More ...
Video - Transport Layer (Layer 4) of OSI Networking Model
In this video by Kevin Wallace you learn about the Transport Layer of the OSI networking model. More ...
Networking Routing Believability and Administrative Distance
If a network is running more than one routing protocol and a router receives two route advertisements from different routing protocols, which route advertisement does the router believe?. More ...
IPv6 Neighbor Discovery Protocol (NDP)
Neighbor Discovery Protocol (NDP) is used by IPv6 hosts for Router Discovery, Neighbor Discovery and Duplicate Address Discovery. More ...
IPv6 Prefix Length Notation
In IPv4, the prefix (or network portion) of the address can be identified by a dotted-decimal netmask, commonly referred to as a subnet mask. IPv6 address prefixes can be represented much the same way that IPv4 address prefixes are written in CIDR notation. More ...
The OSI Data Link Layer
The Data Link layer uses MAC addresses is to pass data frames from the Physical layer to the Network layer and vice versa. The use of MAC addresses permits the direction of data within the same network, but not across routers. More ...
IP Addressing and Subnetting
Today, many different kinds of devices can communicate on a network. A network device might be a computer, a router, a printer, or any number of unusual devices. Every device on a network that uses the Internet protocol (IP) needs a unique IP address. More ...
What's the Difference Between a Packet and a Frame?
When speaking of the data in a network, people often call everything a packet. A more proper generic term would be protocol data unit or PDU. The specific name for a PDU depends on at what layer the data unit is in the OSI model. More ...
Session Border Controllers - More Than Just a Voice Firewall
The migration from Time-Division Multiplexing to the more flexible IP based SIP networks brought an unexpected security challenge. Session Border Controllers focused primarily on SIP and H.323 session security. More ...
Looking at the OSI 7 Layer Reference Model
The OSI (Open Systems Interconnection) model is a 7 layer reference model for how applications can communicate over a network. Don't confuse The OSI model with TCP/IP Protocol which has 4 layers and is the actual architecture used for networking. More ...
