Wide Area Networking Lecture Notes PDF

Wide Area Networking Network Systems CRICOS No.00213J  Module Objectives By the end of this module, you should be able to: 1. Identify the fundamental elements of WAN service options 2. Explain how routers manage internet...

Wide Area Networking Network Systems CRICOS No.00213J  Module Objectives By the end of this module, you should be able to: 1. Identify the fundamental elements of WAN service options 2. Explain how routers manage internetwork communications 3. Compare and contrast WAN connectivity technologies 4. Explain the most common wireless WAN technologies Not covered in the lecture 5. Troubleshoot common connection problems Chapter 9 from Jill West, CompTIA Network+ Guide to Networks, 9th Edition. © 2022 Cengage CRICOS No.00213J  WAN Essentials A WAN traverses a significant distance and usually supports very high data throughput Type of WAN needed depends upon the following factors: Traffic load, budget, geographic breadth, and commercially available technology WAN and LAN differences include the following: LANs connect nodes; WANs connect networks spread over wide geographic area Differ at Layers 1 and 2 access methods, topologies, media Both LANs and WANs use the same protocols from Layer 3 and higher LANs are typically privately owned WANs are typically owned and operated by telcos, also known as NSPs (network service providers) CRICOS No.00213J  Entry Point Equipment (1 of 3) If you have DSL or cable Internet service, you connect your home router to a modem A modem is a modulation/demodulation device that converts digital and analog signals Data Terminal Equipment (DTE) is the customer’s endpoint device on the WAN Communicates on the LAN and is usually owned by the customer Data Communications Equipment (DCE) is the carrier’s endpoint device for the WAN Communicates on the WAN and is usually owned by the ISP Equipment located on the customer’s premises is called CPE (customer premises equipment) Demarc (demarcation point) is the point where the carrier’s responsibility ends and the customer’s responsibility begins CRICOS No.00213J  Entry Point Equipment (2 of 3) Figure 9-2 A router and a modem define the endpoints where a LAN connects to a WAN CRICOS No.00213J  Entry Point Equipment (3 of 3) The following are devices commonly found near the demarc: NIU (network interface unit) – connects the ISP’s local loop to the customer’s network Line driver – essentially a repeater that can boost the signal across greater distances CSU/DSU (channel service unit/data service unit) – serves as the endpoint for a dedicated connection between an ISP and a customer CRICOS No.00213J  Routing Protocols (1 of 3) A router joins two or more networks and passes packets from one network to another Routers can do the following: Connect dissimilar networks (LANs and WANs) Interpret Layer 3 and often Layer 4 addressing Determine the best path for data to follow from point A to point B Reroute traffic if the path of first choice is down but another path is available Routers may perform any of the following optional functions: Filter broadcast transmissions Prevent certain types of traffic from getting to a network Support simultaneous local and remote connectivity Provide high network fault tolerance through redundant components Monitor network traffic and report statistics CRICOS No.00213J Diagnose internal or other connectivity problems and trigger alarms  Routing Protocols (2 of 3) Router categories: Core routers, also called interior routers, direct data between networks within the same autonomous system (AS) Edge routers, or border routers, connect an autonomous system with an outside network Exterior routers refers to any router outside the organization’s AS Direct data between autonomous systems CRICOS No.00213J  Routing Protocols (3 of 3) Figure 9-4 Core, edge, and exterior routers CRICOS No.00213J  Routing Tables (1 of 2) A routing table is a database that holds information about where hosts are located and the most efficient way to reach them Routers rely on them to identify which router is the next hop to reach a particular destination host Routing tables contain IP addresses and network masks that identify a network that a host or another router belongs to CRICOS No.00213J Routing Tables (2 of 2) CRICOS No.00213J  Routing Path Types Routing paths are determined in one of two ways Static routing – A network administrators configures a routing table to direct messages along specific paths Example - a static route between a small business and its ISP Dynamic routing – A router automatically calculates the best path between two networks and maintains this information in a routing table The router can detect problems with failed or congested routes and reroute messages through a different path CRICOS No.00213J  route The route utility allows you to view a host’s routing table The route command can also be used to add or delete static routes The following are some variations of the route command for different operating systems: On a Linux or UNIX system, use the command route On a Windows-based system, use the command route print On a Cisco IOS, use the command show ip route CRICOS No.00213J  Routing Metrics Routing metrics are properties of a route used by routers to determine the best path to a destination: Hop count Theoretical bandwidth and actual throughput Delay, or latency, on a potential path Load, or the traffic or processing burden MTU (maximum transmission unit), or the largest IP packet size in bytes allowable without fragmentation Routing cost, or a value assigned to a particular route Reliability of a potential path Topology of a network Wireless link quality Energy cost CRICOS No.00213J  Routing Protocols to Determine Best Paths Routing protocols are used by routers to communicate with each other to determine the best path Routers rate the reliability and priority of a routing protocol’s data based on these criteria: AD (administrative distance) – a number indicating the protocol’s reliability Convergence time – the time it takes to recognize a best path in the event of a change or network outage Overhead – the burden placed on the underlying network to support the protocol CRICOS No.00213J  Interior and Exterior Gateway Protocols (1 of 5) IGPs (interior gateway protocols) are routing protocols used by core routers and edge routers within autonomous systems and are often grouped according to the algorithms they use to calculate best paths: Distance-vector routing protocols calculate path on the basis of the distance to that destination Link-state routing protocols enables routers to communicate beyond neighboring routers in order to independently map the network and determine the best path EGPs (exterior gateway protocols) are used by edge routers and exterior routers to distribute data outside of autonomous systems The only EGP currently in use is BGP CRICOS No.00213J  Interior and Exterior Gateway Protocols (2 of 5) Figure 9-6 BGP is the only routing protocol that communicates across the Internet CRICOS No.00213J  Interior and Exterior Gateway Protocols (3 of 5) OSPF (Open Shortest Path First) is an IGP and a link-state protocol used on interior or border routers Characteristics include the following: Supports large networks - imposes no hop limits (unlike RIP) Complex algorithm – calculates a more efficient best path Shared data – maintains a database of other routers’ links Low overhead, fast convergence – demands more memory and CPU power for calculations, but keeps network bandwidth to a minimum and provides a very fast convergence time Stability – uses algorithms that prevent routing loops Uses Dijkstra's shortest path algorithm Multi-vendor routers – supported by all modern routers CRICOS No.00213J  OSPF in detail CRICOS No.00213J  Interior and Exterior Gateway Protocols (4 of 5) IS-IS (Intermediate System to Intermediate System) is an IGP and link-state routing protocol It uses a best-path algorithm similar to OSPF’s It is designed for use on core routers only (unlike OSPF) More easily adaptible to IPv6 EIGRP (Enhanced Interior Gateway Routing Protocol) is an advanced distance-vector protocol that combines some of the features of a link-state protocol It is often referred to as a hybrid protocol Offers fast convergence time and low network overhead It is easier to configure and less CPU-intensive than OSPF Supports multiple protocols and limits unnecessary network traffic between routers EIGRP was originally proprietary to Cisco routers CRICOS No.00213J  Interior and Exterior Gateway Protocols (5 of 5) BGP (Border Gateway Protocol) is the only current EGP and is known as the “protocol of the Internet” BGP spans multiple autonomous systems Special characteristics of BGP include the following: Path-vector routing protocol ▶ Communicates via BGP-specific messages that travel between routers over TCP sessions Efficient ▶ Uses many factors to determine best paths Customizable ▶ Can be tailored to avoid certain routers or give preference to some routers BGP is the most complex of the routing protocols mentioned in this module CRICOS No.00213J  Routing Redundancy Large networks should have multiple ISP connections with each using geographically separate hardware and network media Two redundancy techniques include the following: Active-active redundancy – all redundant resources are active at all times, and work is distributed among them Active-passive redundancy – only one or a few redundant resources are active at any time with the backup devices on standby FHRP (First Hop Redundancy Protocol) can be used to provide a VIP (virtual IP) address as the default gateway This IP address can potentially point to multiple routers VRRP (Virtual Router Redundancy Protocol) Industry standard Specifies one primary and other backup routers Proprietary to CISCO HSRP (Hot Standby Routing Protocol) ▶ One primary, one standby, and other backup routers GLBP (Gateway Load Balancing Protocol) ▶ Gateways weighted according to priority ▶ Traffic is load-balanced among all gateways CRICOS No.00213J  WAN Connectivity WAN connectivity options include the following: Broadband – cables and bandwidth are shared between multiple customers The ISP makes a “best effort” attempt to provide up to advertised bandwidth Bandwidth is asymmetrical (asynchronous) which means download speeds are faster than upload speeds DIA (dedicated internet access) – bandwidth is dedicated to a single customer Bandwidth is symmetrical (synchronous) which means download and upload speeds are about the same This is important for businesses that back up large amounts of data online CRICOS No.00213J  DSL (Digital Subscriber Line) (1 of 2) DSL (digital subscriber line) is a WAN connection method that operates over the PSTN (public switched telephone network) DSL supports multiple data and voice channels over a single line It requires repeaters for longer distances The distance between the customer and CO affect actual throughput DSL uses advanced data modulation techniques A DSL connection might use a modulation technique based on amplitude or phase modulation to alter the waves at higher frequencies to carry data CRICOS No.00213J  DSL (Digital Subscriber Line) (2 of 2) The types of DSL vary according to their throughput rates, data modulation techniques, capacity, and distance limitations xDSL refers to all DSL varieties and the x is replaced by the variety’s name Better-known DSL varieties: ADSL (asymmetric DSL) – faster download speeds than upload speeds Most common form of DSL Best use of ADSL is video conferencing and web surfing VDSL (very high bit rate DSL or variable DSL) – faster than ADSL and is also asymmetric SDSL (symmetric DSL) – has equal download and upload speeds maxing out around 2 Mbps Best use of SDSL is uploading and downloading significant data amounts CRICOS No.00213J  Cable Broadband (1 of 3) Cable broadband (also called cable Internet or cable modem access) is based on coaxial cable wiring used for TV signals Cable broadband was standardized by an international cooperative effort It yielded a suite of specifications called DOCSIS (Data Over Cable Service Interface Specifications) Service is typically offered at asymmetric speeds Such as up to 70 Mbps download and 7 Mbps upload The newest DOCIS standard is 4.0 and allows for symmetric multi-gigabit speeds up to 10 Gbps downstream and 6 Gbps upstream HFC (hybrid fiber coaxial) networks use fiber-optic cabling to connect the cable company’s distribution center to distribution hubs and then to optical nodes near customers CRICOS No.00213J  Cable Broadband (2 of 3) Figure 9-13 HFC infrastructure CRICOS No.00213J  Cable Broadband (3 of 3) A cable modem modulates and demodulates signals for transmission and reception via cable wiring They operate at the physical and data Link layers of the OSI model A cable modem may connect to connectivity device such as a router or switch It is possible to use a device that combines cable modem functionality with a SOHO router to share available bandwidth on an entire network Cable broadband provides a dedicated and continuous connection It does require many subscribers to share the same local line which raises concerns about security and actual throughput CRICOS No.00213J  Fiber (1 of 2) A growing trend in ISP offerings for WAN connection services is to offer the following: FTTN (fiber-to-the-node or fiber-to-the- neighborhood) FTTC (fiber-to-the-curb) FTTB (fiber-to-the-building) or FTTH (fiber-to-the-home) MONs (metropolitan optical networks) bring fiber to the customer Image courtesy of IEEE CRICOS No.00213J  Fiber (2 of 2) Figure 9-16 Getting fiber close to your own network increases your Internet speeds CRICOS No.00213J  Leased Lines Leased lines provide dedicated bandwidth on fiber optic connections A dedicated line offers the following advantages: Dedicated bandwidth Symmetrical bandwidth SLA-backed guarantee Ongoing monthly costs of a leased line vary greatly depending on many factors: Required bandwidth The distance to the ISP’s exchange or between the company’s own locations CRICOS No.00213J  MPLS (Multiprotocol Label Switching) (1 of 2) MPLS (multiprotocol label switching) enables multiple types of Layer 3 protocols to travel over any one of several connection-oriented Layer 2 protocols MPLS can handle various types of payloads It is often used by ISPs on their own networks for moving traffic from one customer site to another MPLS labels include information about where the router should forward the message next The labels may also include prioritization information The primary benefits of MPLS include the following: MPLS connections are highly scalable for business Customers can prioritize their own traffic across the WAN The ability to label traffic offers more reliability, predictability, and security CRICOS No.00213J  MPLS (Multiprotocol Label Switching) (2 of 2) Figure 9-20 Label switching routers simply forward the message without calculating routes CRICOS No.00213J  Cloud Connectivity Options Figure 9-21 A colocation facility offers connections to multiple cloud platforms CRICOS No.00213J  Software-defined WAN (SD-WAN) (1 of 2) SD-WAN (software-defined wide area network) relies on abstracted, centralized control of networking devices to manage network functions across a diverse infrastructure SD-WAN offers the following benefits: Transport agnostic Can manage network configurations regardless of the type of connection used to reach SD-WAN (Cable, DSL...) Active-active load balancing and automatic failover Can dynamically determine how to use existing connections for balancing traffic based on set traffic priorities Intent-based management For instance, network admins can limit bandwidth for a specific application Zero-touch provisioning Can be deployed at a remote site without local technical expertise Reduced cost CRICOS No.00213J Can be effective in replacing MPLS or leased lines  Software-defined WAN (SD-WAN) (2 of 2) Figure 9-23 The SD-WAN controller can direct traffic through the optimal path for that traffic at a given time CRICOS No.00213J  Wireless WANs Wireless WANS are specifically designed for high-throughput; long-distance digital data exchange CRICOS No.00213J  Cellular (1 of 2) Cellular networks were initially designed for analog phone service Today it can deliver data and voice Cellular technology generations include the following 1G (first generation) were analog 2G (second generation) used digital transmission up to 240Kbps 3G (third generation) supported data rates up to 384Kbps Data communications use packet switching 4G (fourth generation) services are characterized by an all-IP network for data and voice Specifies throughputs of 100 Mbps to 1 Gbps speeds 5G (fifth generation) services require minimum speeds of 1 Gbps and max out at 20 Gbps and upload speeds of 10 Gbps CRICOS No.00213J  Cellular (2 of 2) Figure 9-25 Cellular network CRICOS No.00213J  Satellite (1 of 2) Today, satellites are used for transmitting consumer voice, video, music, and data Satellite orbits Most satellites circle the Earth in a geosynchronous orbit GEO (geosynchronous earth orbit) satellites orbit at the same rate the Earth turns Information is transmitted to the satellite in an uplink from an Earth-based transmitter A satellite transponder transmits signal to Earth-based transmitter in a downlink GEO satellites are the type used by the most popular satellite data service providers Satellite Internet services A handful of companies offer high-bandwidth Internet access via GEO satellite links Satellite services are typically asymmetrical, and bandwidth is shared among many subscribers Throughputs vary and are controlled by the service provider CRICOS No.00213J  Satellite (2 of 2) Figure 9-27 Satellite communication CRICOS No.00213J  Summary Now that the lesson has ended, you should be able to: Identify the fundamental elements of WAN service options Explain how routers manage internetwork communications Compare and contrast WAN connectivity technologies Explain the most common wireless WAN technologies Troubleshoot common connection problems CRICOS No.00213J