Understanding Wide Area Networks Module 7 Objectives Skills/Concepts Objective Domain Objective Domain Description Number Understanding routing Understanding routers 2.2 Defining common WAN Understanding wide area 1.3 technologies and networks (wan’s) connections Routing • 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 Static Dynamic 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 • Link state routing protocols: Provide updates only when a network link changes state • Distance Vector Routing • Routing Information Protocol (RIP) • Link State Routing • 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 AS RIP RIP AS OSPF OSPF 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 AS BGP AS RIP RIP OSPF OSPF DEMO: Configuring RRAS Server (verify RIP) Wide Area Network • Wide area networks (WANs) connect multiple local area networks together • WANs connect multiple LANs that can include a home, school, or buildings • WANs 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 • WANs utilize some type of packet switching technology • Packet switching services include X.25 and Frame Relay • Before packet switching, technology such as direct dial-up connections was used X.25 • 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 Modem (DCE) X.25 Network DTE 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 Hops • 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 • X.25 allows shared access among multiple users on the LAN • X.25 has full error and flow control • There is also 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 are 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 • Leased lines are a 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 T-Carrier Systems Comparison • Countries and their associated T-carrier systems T-Carrier North America Japan Europe Level 0 – DS0 64 Kbps 64 Kbps 64 Kbps Level 1 – DS1 1.544 Mbps (T1: 24 user 1.544 Mbps (J1: 24 1.544 Mbps (E1: 24 user Channels) user Channels) Channels) Level 3 – DS3 44.736 Mbps (T3: 672 32.064 Mbps (J3: 34.368 Mbps (E3: 512 user user channels) 480 user channels) channels) Level 4 – DS4 274.176 Mbps (T4: 4032 97.728 Mbps (J4: 139.264 Mbps (E4: 2048 user channels) 1440 user channels) user channels) ISDN A digital technology developed to offer faster communication speed than an analog telephone line • Integrated Services Digital Network (ISDN) is a 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 ATM • Asynchronous transfer mode (ATM) is a 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 SONET • Synchronous Optical Networking (SONET) is a 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 SONET Signal Hierarchy Level Line Rate DS3 Channels OC-1 51.84 Mbps 1 OC-3 155.52 Mbps 3 OC-12 622.08 Mbps 12 OC-24 1.244 Gbps 18 OC-48 2.488 Gbps 48 OC-192 9.953 Gbps 192 FDDI • Fiber distributed data interface (FDDI) is a 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 DSL • Digital subscriber line (DSL) is a 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 • Broadband cable is 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 384 kbps to 20 Mbps + POTS/PSTN • POTS/PSTN stands for plain old telephone system/public switched telephone network.