Introducing WAN Technologies Flashcards
Service provider networks are complex. They are mostly built of high-bandwidth fiber-optic media, using Dense Wavelength Division Multiplexing (DWDM), the Synchronous Optical Networking (SONET) in North America, and Synchronous Digital Hierarchy (SDH) in the rest of the world. These standards define how to transfer data over optical fiber over great distances
Dense Wavelength Division Multiplexing (DWDM)
Synchronous Optical Networking (SONET) - in North America
Synchronous Digital Hierarchy (SDH) - in the rest of the world
Are devices that modulate and demodulate analog carriers to encode and retrieve digital information. A modem interprets digital and analog signals, enabling data to be transmitted over voice-grade telephone lines.
Modems
Are used where a fiber-optic link terminates to convert optical signals into electrical signals and vice versa. You can also implement the converter as a router or switch module.
Optical fiber converters
provides internetworking and WAN access interface ports that are used to connect to the service provider network. These interfaces may be serial connections or other WAN interfaces. With some types of WAN interfaces, you need an external device such as a CSU/DSU or modem (analog, cable, or DSL) to connect the router to the local point of presence (POP) of the service provider.
router
Resides within the middle or backbone of the WAN, rather than at its periphery. To fulfil this role, a router or multilayer switch must be able to support multiple telecommunications interfaces of the highest speed in use in the WAN core. It must also be able to forward Internet Protocol (IP) packets at wire speed on all these interfaces.
core router or multilayer switch
Are used when you are using the wireless medium for WAN connectivity. You can also use an access point instead of a wireless router.
Router with cellular connectivity features
Data terminating equipment (DTE) and data communications equipment (DCE) are terms that were used in the context of WAN connectivity options that are mostly considered legacy today. The two terms name two separate devices. The DTE device is either a source or a destination for digital data. Specifically, these devices include PCs, servers, and routers. In the figure, a router in either office would be considered a DTE. DCE devices convert the data received from the sending DTE into a form acceptable to the WAN service provider.
DTE - (Data terminating equipment)
DCE - (Data communications equipment)
Is a marking which separates a customer’s WAN equipment from the service provider’s equipment.
demarcation point
The customer side of the demarcation point accommodates
Customer Premises Equipment (CPE)
This topology establishes a circuit (a logical connection) between exactly two sites. It is also called a Layer 2 service as it creates a connection, via which it seems that both sites are on the same physical segment.
Point-to-point topology
This topology features a central router or multilayer switch, acting as the hub, which is connected to all other remote devices, the spokes. All communication among the spoke networks traverses the hub.
Hub-and-spoke topology
In this topology, each remote node on the periphery of a given service provider network has a direct logical connection, also called a circuit, to every other remote node. Any site can communicate directly with any other site. The key rationale for creating a full mesh environment is to provide a high level of redundancy.
Full mesh topology
In this topology, almost, but not all remote nodes are inter-connected. It reduces the number of sites that have direct connections to all other nodes. Partial meshes are highly flexible topologies that can take various very different configurations.
Partial mesh topology
Which provide permanent dedicated connections using point-to-point links with various capacities that are limited only by the underlying physical facilities and the willingness of enterprises to pay for these dedicated lines. A point-to-point link provides a pre-established WAN communications path from the customer premises through the provider network to a remote destination.
Dedicated communication links
Can be either circuit-switched or packet-switched. It is important to differentiate between the two switching models
Switched communication links
Circuit switching establishes a dedicated virtual connection, called a circuit between a sender and a receiver. The connection through the network of the service provider is established dynamically, before communication can start, using signaling which varies for different technologies.
Circuit-switched communication
Using circuit switching does not make efficient use of the allocated fixed bandwidth due to the data flow fluctuations. In contrast to circuit switching, packet switching segments data into packets that are routed over a shared network
Packet-switched communication
Instead of using a separate WAN infrastructure, enterprises today commonly take advantage of the global internet infrastructure for WAN connectivity. Previously, the internet was not a viable option for a WAN connection due to many security risks and lack of SLA, i.e. the lack of adequate performance guarantees.
Internet-based communication links
Is a Layer 2 technology which defines virtual circuits (VCs). Each VC represents a logical end-to-end link mapped over the physical service provider’s Frame Relay WAN. An enterprise can use a single router interface to connect to multiple sites using different VCs.
Frame Relay
Is built on a cell-based architecture rather than on a frame-based architecture. ATM cells are always a fixed length of 53 bytes. Small, fixed-length cells are well-suited for carrying voice and video traffic because this traffic is intolerant of delay. Video and voice traffic do not have to wait for larger data packets to be transmitted.
ATM technology
Is an Internet Engineering Task Force (IETF) standard that defines a packet label-based switching technique, which was originally devised to perform fast switching in the core of IP networks. This technique helped carriers and large enterprises scale their networks as increasingly large routing tables become more complex to manage.
MPLS (Multipleprotocol Label Switching)
