Shared Flashcard Set


7.Understanding Wide Area Networks
From the MVA course "Networking Fundamentals"
Computer Networking

Additional Computer Networking Flashcards




Routing is the process of managing the flow of data between network segments and between hosts or routers.
Data is sent along a path according to the IP networks and individual IP addresses of the hosts.
A router is a network device that maintains tables of information about other routers on the network or internetwork.
Static and Dynamic Routing
A static route is a path that is manually configured and remains constant throughout the router ’s operation.
A dynamic route is a path that is generated dynamically by using special routing protocols.

Dynamic Routing
Dynamic routing method has two conceptual parts:
Routing protocol used to convey information about the network environment
Routing Algorithm that determines paths through the network
Common Dynamic routing protocols
Distance vector routing protocols: Advertise the number of hops to a network destination (distance)
and the direction a packet can reach a network destination (vector). Sends updates at regularly
scheduled intervals, and can take time for route changes to be updated.
Routing Information Protocol (RIP)

Link state routing protocols: Provide updates only when a network link changes state.
Open Shortest Path First (OSPF)
Interior Gateway Protocols (IGPs)
Routing protocols that enable elements that comprise an autonomous system (AS) to exchange routing information.
For very large networks it is necessary to divide the internetwork into entities known as autonomous systems (AS).
IGPs exchange routing information within a single AS that operates common routing protocols.
RIP and OSPF are examples of IGPs.
Routing Information Protocol (RIP and RIPv2)
Distance vector routing protocol that enables the exchange of IP routing information.
Calculates the direction or interface that packets should be forwarded to, as well as the distance from the destination.
Each router maintains a database of the number of hops to a network destination (distance) and the direction a packet can reach a network destination (vector).
RIP is easy to implement and has a large installed base.
Updates are sent periodically.
Open Shortest Path First (OSPF)
A link-state protocol that monitors the network for routers that have a change in their link state.
Each router maintains a database of router advertisements called Link State Advertisements (LSAs).
An LSA consist of a router, attached networks and their configured costs.
Updates are sent when the status of a route is updated.
Exterior Gateway Protocols (EGPs)
A routing protocol that was designed and intended for use between autonomous systems.
Border Gateway Protocol (BGP) is an EGP that enables autonomous systems (AS) to exchange routing information.
BGP is used to enable routing on the Internet.
Wide Area Networks
Connect multiple LANs that can include a home, school, or buildings. Enable network to function without concern to a location.
WAN technologies can include :
Packet Switching
Devices transport packets via shared links.
Leased Line
Dedicated point to point connection.
Circuit Switching
Dedicated circuit path is created between end points (dial up).
Cell Relay
Similar to packet switching but uses fixed packet lengths.
Packet Switching
Packet switching services include X.25 and Frame Relay.
Before packet switching, technology such as direct dial-up connections was used.
X.25 communications protocol was one of the first implementations of packet switching
Data Terminal Equipment (DTEs) or a network device, connect to Data Communications Equipment (DCEs), a modem is a DCE enabling communication to the X.25 network.
Dummy terminals can connect to the network using Packet Assembler/Disassembler (PADs) which connect to the DCE.
Virtual Circuits
Telecommunication companies have thousands of shared circuits / connections from which to select a path.
These are known as a circuit set.
The chances of the entire message of packets taking one circuit are slim. Multiple circuits are being used, and not just one, the entire circuit set is known as the virtual circuit.
This method of data transmission is the core technology for the Internet and most LANs.
There could be several PSE stops along the way. These PSEs disassemble and reassemble the packets.
These stops are also known as hops.
At the receiving office, the packet is reassembled and the overhead (header and trailer) is discarded
X.25 advantages
If data fails, X.25 automatically recovers and sends it again.
Allows shared access among multiple users on the LAN.
Has full error and flow control.
Protection from intermediate link failure.
X.25 is not completely fault tolerant, but it is 70% effective.
Pricing is per shared packet sent, not per minute.
X.25 is a synchronous, digital transmission. There is less overhead per file.
Frame Relay
Frame Relay is the advancement of X.25 packet switching.
A standardized wide area network protocol using a form of packet switching designed for faster connections.
It also uses a virtual circuit, but one that is more advanced. Frame Relay created the “virtual network” that resides in the cloud.
Permanent Virtual Circuits
A permanent virtual circuit is a virtual circuit established for repeated use.
Frame Relay enables multiple sessions to be run simultaneously on the same link.
These connections to the cloud are known as permanent logical links or permanent virtual circuits (PVCs).
The PVC links the sites together in the cloud, and this is accomplished by using the PSE (packet switching exchange).
Leased Lines
Connection contract between a provider and a customer.
Frame Relay service must be purchased from an Internet services or telecommunications provider.
With Frame Relay, you must commit to a certain amount of information over time.
This is the CIR (committed information rate). The CIR is assigned to each PVC that services the organization’s account.
Because this transmission is full duplex, there can be two CIRs for each PVC.
T-Carrier Overview
A T-carrier or telecommunications carrier system is a cabling and interface system designed to carry data at high speeds.
The basic data transfer rate of the T-carrier system is 64 Kbps, which is known as DS0, which is the digital signaling scheme.
DS1 is the digital signaling scheme for the T1-carrier.
Integrated Services Digital Network (ISDN)
A digital technology developed to offer faster communication speed than an analog telephone line.
Set of communication standards enabling simultaneous digital transmission of data, fax, voice and video.

ISDN can be broken down into two major categories:
Basic rate ISDN (BRI)
128 Kbps - two equal B channels at 64 Kbps each
Generally, devices that connect to BRI lines can handle eight simultaneous connections to the Internet.
Primary rate ISDN (PRI)
1.536 Mbps - runs on a T-1 circuit
24 equal 64 Kbps B channels for data
Asynchronous transfer mode (ATM)
Cell-based switching technology as opposed to a packet switching technology.
ATM is a high-speed networking technology used to transmit data in cells of a fixed length containing 53 bytes of information.
ATM is a native connection-oriented protocol comprised of a number of related technologies for software, hardware and connection oriented matter.
Synchronous Optical Networking (SONET)
Standardized protocol allowing for the transmissions of signals over optical fiber in North America.
Synchronous Digital Hierarchy (SDH) is the standard in Europe
The standard represents a transport vehicle capable of supporting data rates in the gigabit range, optical interfaces, network management and testing methods.
Before the standard was released, each manufacturer designed its fiber terminal device to its own optical signal interface.
Fiber distributed data interface (FDDI)
Standard for transmitting data on fiber optic cables at a rate of around 100 Mbps.
Supports transmission distances beyond 50 miles.
The original FDDI standard called for a physical double ring topology.
FDDI is primarily a protocol used on backbone networks.
Digital subscriber line (DSL)
Family of technologies that provides data transmissions over local telephone networks.
DSL allows for voice and data to be run over the same line.
DSL uses higher frequency bands to transmit data.
xDSL is the standard for the various digital subscriber lines.
ADSL (asymmetric digital subscriber lines) The upload and download speed are the different or asymmetrical.
SDSL (symmetrical digital subscriber line) The upload and download speed are the same or symmetrical
Broadband cable
Used for cable Internet and cable television using the cable television network.
It operates at a higher speed than DSL and rates can range from 384kbps to 20 Mbps +
Stands for plain old telephone system/public switched telephone network.
This is what we use now for “regular ” phone lines, and it has been around since the 1940s.
POTS/PSTN is now digital at the switching office and some central offices, but there analog lines run to people’s homes.
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