Chapter2 (2).pptx

Chapter 2: WAN Concepts CCNA Routing and Switching Connecting Networks v6.0 Purpose of WANs Why a WAN?  A WAN operates beyond the geographic scope of a LAN.  WANs are used to interconnect the enterprise LAN to remote LANs in...

Chapter 2: WAN Concepts CCNA Routing and Switching Connecting Networks v6.0 Purpose of WANs Why a WAN?  A WAN operates beyond the geographic scope of a LAN.  WANs are used to interconnect the enterprise LAN to remote LANs in branch sites and telecommuter sites.  A WAN is owned by a service provider whereas a LAN is typically owned by an organization.  An organization must pay a fee to use the WAN service provider’s network services to connect remote sites.  Service providers provide links to interconnect remote sites for the purpose of transporting data, voice, and video. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 2 Purpose of WANs  Without WANs, LANs would be a series of Are WANs Necessary? isolated networks.  As organizations expand, businesses require the ability to communicate between geographically separated sites. For example: Regional or branch offices of an organization need to be able to communicate and share data with the central site. Organizations need to share information with other customer organizations. Employees who travel on company business frequently need to access the corporate network.  In addition, consumers now commonly communicate over the Internet with banks, stores, and other providers of goods and services. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 3 Purpose of WANs  Interconnecting multiple sites across WANs can involve a variety of service provider technologies and WAN Topologies WAN topologies. There are four Common WAN topologies.  Point-to-Point topology Employs a point-to-point circuit between two endpoints Typically involves a dedicated leased-line connection such as a T1/E1 line. Transparent to the customer network and appears to be a direct physical link between two endpoints  Hub-and-Spoke Applicable when a private network connection between multiple sites is required A single interface to the hub can be shared by all spoke circuits. Spoke sites can be interconnected through the hub site using virtual circuits and routed subinterfaces at the hub. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 4 Purpose of WANs WAN Topologies (Cont.)  Full Mesh A disadvantage of the hub-and-spoke topology is that all communication has to go through the hub. With a full mesh topology using virtual circuits, any site can communicate directly with any other site. A disadvantage is the large number of virtual circuits that need to be configured and maintained.  Dual-homed Topology Provides redundancy and load balancing however they are more expensive to implement than single- homed topologies. Requires additional networking hardware including routers and switches. More difficult to implement since they require complex configurations. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 5 Purpose of WANs  In slow economic times, many Evolving Networks businesses focus on increasing their profitability by improving the efficiency of their existing operations – including establishing and managing their network.  To justify such a large expense, many companies expect their networks to perform optimally and to be able to deliver an increasing array of services and applications to support productivity and profitability.  This chapter will focus on a fictitious company called SPAN Engineering.  This topic will illustrate how SPAN’s network requirements change as the company grows from a small, local business into a global enterprise © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 6 Purpose of WANs  SPAN Engineering: Small Office Environmental consulting firm (4 years) Has developed a special process for converting household waste into electricity and is developing a small pilot project for a municipal government in its local area. 15 employees: six engineers, four computer-aided drawing (CAD) designers, a receptionist, two senior partners and two office assistants Small office uses a single LAN to share information between computers, support their VoIP phones, share peripherals, printer, and large-scale plotter Connects to the Internet using DSL Uses support services purchased from DSL provider for IT support. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 7 Purpose of WANs  Five years later, SPAN Engineering has Campus Network grown rapidly. The company was contracted to design and implement a full-sized waste conversion facility as well as other projects in neighboring municipalities and around the country.  The company is now classified as a small to medium-sized business with several hundred employees.  The company now occupies multiple floors of an office building.  The network has grown to several subnetworks which spans several floors of the building.  The business now has an in-house IT staff to support and maintain the network © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 8 Purpose of WANs  Another six years later, SPAN Branch Networks Engineering has been so successful, they have expanded their operation and have opened small branch offices closer to the project sites.  The company was required to implement a WAN in order for the remote sites to be able to access the data center which houses various databases and servers.  The branch offices that are in nearby cities use private dedicated lines through their local service provider.  Offices that are located in other countries must use the Internet for their WAN connection. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 9 Purpose of WANs  SPAN Engineering has now been in Distributed Network business for 20 years and has grown to thousands of employees distributed in offices worldwide.  The cost of the network and its related services is a significant expense.  To increase profitability, the company must reduce its operating expense. What methods has the company used to reduce its operating costs?  To meet the new requirements, the network must provide the necessary converged service and secure Internet WAN connectivity to remote sites.  As seen in this example, network requirements of a company can change dramatically as a company grows over time. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 10 WAN Operations  WAN operations focus primarily on the physical WANs in the OSI Model and data link layer of the OSI Model.  Data link layer requirements include physical addressing, flow control and encapsulation.  WAN access standards are defined and managed by a number of recognized authorities: TIA/EIA (Telecommunications Industry Association and the Electronic Industries Alliance) ISO (International Organization for Standardization) IEEE (Institute of Electrical and Electronics Engineers)  Layer 1 protocols describe how to provide electrical, mechanical, operational, and functional connects to the services of a communications service provider.  Layer 2 protocols define how data is encapsulated and the mechanisms for transferring the resulting frames © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11 WAN Operations  One primary difference between a WAN Common WAN Terminology and a LAN is that a company must subscribe to an outside WAN service provider to use WAN carrier network services.  Terminology commonly used to describe WAN connections: Customer Premises Equipment (CPE) – Consists of devices and inside wiring located on the enterprise edge connecting to a carrier Data Communications Equipment (DCE) – Also called circuit-terminating equipment, the DCE consists of devices that put data on the local loop. The DCE primarily provides an interface to connect subscribers to a communication link on the WAN cloud. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 12 WAN Operations Data Terminal Equipment (DTE) – The Common WAN Terminology (Cont.) customer devices that pass the data from a customer network or host computer for transmission over the WAN. The DTE connects to the local loop through the DCE. Demarcation Point – This is a point established in a building to separate customer equipment from service provider equipment. Local Loop (“last mile”) – The actual copper or fiber cable that connects the CPE to the CO of the service provider. Central Office (CO) – The CO is the local service provider facility or building that connects the CPE to the provider network. Toll network – This consists of the long-haul, all-digital, fiber-optic communications lines and other equipment inside the WAN provider network. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 13 WAN Operations  There are many types of devices that are WAN Devices specific to WAN environments: Dialup modem – Legacy WAN technology that converts (modulates) the digital signals produced by a computer into voice frequencies which are transmitted over the analog lines of the public telephone network to another modem for demodulation. Access server – Legacy technology where the server controls and coordinates dialup modem, dial-in and dial-out user communications. Broadband modem – A type of digital modem used with high-speed DSL or cable Internet service. Both operate in a similar manner to the voiceband modem, but use higher broadband frequencies and transmission speeds. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 14 WAN Operations CSU/DSU - Digital-leased lines WAN Devices (Cont.) require a CSU and a DSU. The CSU provides termination for the digital signal and ensures connection integrity through error correction and line monitoring. The DSU converts line frames into frames that the LAN can interpret and vice versa. Router – Provides internetworking and WAN access interface ports that are used to connect to the service provider. Core router/Multilayer switch – A router or multilayer switch that resides within the middle or backbone of the WAN. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 15 WAN Operations A circuit-switched network is one that Circuit Switching establishes a dedicated circuit (or channel) between nodes and terminals before the users may communicate. Circuit switching dynamically establishes a dedicated virtual connection for voice or data between a sender and a receiver. Communication can't start until the connection is established through the service provider network. Dialing a number to make a call is an example of circuit switching technology. The two most common types of circuit- switched WAN technologies are the public switched telephone network (PSTN) and the Integrated Services © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 16 Digital Network (ISDN). WAN Operations In contrast to circuit switching, packet switching splits traffic data into packets that Packet Switching are routed over a shared network. A circuit does not need to be established and many pairs of nodes can communicate over the same channel. There are two approaches to packet-switched network link determination: Connectionless systems – Full addressing information must be carried in each packet. The Internet is an example of a connectionless system. Connection-oriented systems – The network predetermines the route for a packet, and each packet only has to carry an identifier. An example of a connection-oriented system is Frame Relay (DLCIs are the identifiers). Packet switching costs less than circuit switching, however, latency and jitter are greater in packet-switching networks. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 17