Network Connectivity and Mobility

1. Network Connectivity and Mobility BSAD 141 Dave Novak

2. Topics Covered • Lecture is structured based on the five elements of creating a connected world from the text book (with additional content) • Network Categories • Network Providers • Network Access Technologies • Network Standards and Protocols • Network Convergence

3. A Connected World • Five elements creating a connected world

4. Network Categories • 1) LAN (local area network): a group of computers sharing a common media – usually in a small geographic area such as a building • 2) MAN (metropolitan area network): network larger than a LAN – connects computers over a larger geographic area • 3) WAN (wide area network): largest network that connects various LANs and MANs throughout the world

5. Differences • LANs utilize high-speed, lower-cost shared networking technologies such as Ethernet and WiFi • MANs connect a group of LANs to various network providers such cable TV providers, local ISPs, telecom providers • WANs utilize very different networking technologies than LANs – point-to-point, higher-cost technologies that function across large geographic areas

6. Differences

7. LAN • LANs are categorized as “smaller” networks that used a shared medium to connect computers, printers, and other network devices • Physical LANs are constrained geographically to “small” areas • Buildings or floors of buildings • This is a function of the type of networking technologies used

8. LAN • Computers and other devices such as printers connect to the LAN via switches and/or wireless access points • LANs connect to other larger networks (like MANs and WANs) via routers

9. WAN • WANs are generally categorized as “large” networks that connect other LANs and MANs and operate across large geographical areas • Groups of buildings, Cities or municipalities, regions of a country

10. WAN • WANs use different networking technologies and protocols than LANs – specifically technologies that operate over large areas • Messages that traverse a WAN are passed from one router to another • Routing involves selecting the “best” path through a network

11. LAN

12. WAN

13. Differences • Communication on a wired or wireless LAN does not require the use of a router • Communication off a wired or wireless LAN (to another LAN), WAN, or the Internet requires the use of a router • For example, you can set up a LAN for local communication, but traffic cannot come into the LAN or leave the LAN unless some type of router is used to provide a “doorway” to another network

14. Terminology • The network medium is the physical channel used to transmit data across a network • Copper wires, fiber optics, radio waves…

15. Networking Technology • There are MANY different networking technologies – both for LANs and WANs • Network technology - a standards-based combination of hardware, software, and protocols • Examples of networking technologies: • Ethernet • WiFi • Asynchronous Transfer Mode (ATM)

16. Networking Technology • Ethernet is the most popular and widely used wired LAN networking technology • There are many different Ethernet standards that use different media (different types of cabling), different topologies and support different bandwidths • 10/100/1000

17. Dest. MAC Source MAC Preamble SFD Length DATA FCS 8 bytes 1 6 6 2 46 – 1500 bytes 4 Access Control Frame Control Dest. MAC Source MAC Frame Status Start Del. End Del. DATA FCS 4500 >= 0 4 1 1 1 6 6 1 1 Networking Technology • Ethernet frame (IEEE 802.3) v2 length >= 1536 B • Token Ring frame (IEEE 802.5) length > 4500 B

18. Networking Technology • WiFi is a commonly used wireless technology used on LANs that provides relatively high-speed, but short range connectivity • Benefits • Inexpensive, quick & easy • Drawbacks • Security, distance limitations, speed

19. Networking Technology • What is the difference between WiFi and the general term “wireless”?

20. Source: http://retailtechnologytrends.com/2010/11/05/2010-45-whats-the-difference-between-wifi-and-wireless/

21. Networking Technology • What is Bluetooth?

22. Networking Hardware • Network Interface Card • Switch • Router

23. Network Providers • National service providers (NSPs) - Private companies that own and maintain the backbone networks that support the Internet • Network access points (NAPs) - Traffic exchange / aggregation points in the routing hierarchy of the Internet that connect ISPs • Internet service providers (ISPs) – Regional and local “gateways” to the Internet that connect to NSPs and can connect directly to each other

24. Network Providers

25. Network Terminology • Bandwidth • Throughput

26. Network Terminology • When your ISP uses the term “broadband” what do they mean?

27. Network Access Technologies • Corporate connectivity options • 1) Point-to-point leased lines • 2) Public Telephone Network (PSTN) • 3) Virtual Private Network (VPN) • Home connectivity options • 1) Dialup modem • 2) DSL modem • 3) Cable modem • 4) WiFi

28. Point-to-point Communication • Communication channel rented from a service provider • Using the existing telecommunications infrastructure system • Typically considered a private service • Different technologies and bandwidth options depending on provider • Optical fiber versus copper wire

29. Point-to-point Communication • Customers pay a monthly fee for dedicated use of a communication channel • Fee depends on bandwidth, the networking technology being used, and on Quality-of-Service (QoS) guarantees

30. PSTN • The wired telecommunications network that supports landline telephone usage • This is a circuit-switched network while data networks are packet-switched – the relevance of this statement with respect to our class is that this network is not designed for data usage, but for voice-based phone usage

31. PSTN • PSTNs provide much of the intra and inter-continental (long-distance) communication infrastructure that we consider to be “part of” the internet • Internet Service Providers (ISPs) pay long-distance telecom providers (the owners of the PSTN like MCI, Sprint, AT&T, etc.) for access to their networks – in turn, customers of ISPs pay the ISP

32. PSTN • Users of the public internet (most customers) gain access to the PSTN through their ISP • With respect to home-based users, the PSTN is generally considered to be a shared communication channel

33. Public versus Private?? • Public– users pay fees to use a shared network • Could be “pay-as-you-go” approach • Parts of the physical infrastructure network are available to the general public • Private – users pay fees to obtain a dedicated portion of the network • Usually a “flat fee” approach • Parts of the physical infrastructure network are “set-aside” or dedicated just for the renter

34. Shared versus Dedicated?? • Shared – media / channel capacity is used jointly by multiple users or applications as needed • Envision a toll road • Dedicated– media / channel capacity is used exclusively by a single user or application • Envision a toll road where users paid to reserve their own lane and no one else can use that lane

35. Point-to-Point and PSTN • In many cases we are talking about “classification” or stratification of the same physical infrastructure network… • For example, AT&T can provide users with both options: • Point-to-point services • Public PSTN services

36. Virtual Private Network(VPN) • Relies on PSTN “public / shared” network service but provides users with secure / private access to their organization’s network • Idea is to leverage the low cost of a public / shared network with the security of a private network • Goal – same “security” as point-to-point leased lines at a fraction of the cost

37. Virtual Private Network(VPN) • Accomplished by installing VPN client-side software and having client computers connect directly to the VPN server on the organization’s “home” network • Uses special “tunneling protocols” to encrypt data at the sending end and decrypt the data at the receiving end essentially masking or hiding the private information • PPTP, L2TP

38. Virtual Private Network(VPN) • VPN requires special software for each connected site • Allows only secure communication between remote host and VPN server – protects from unauthorized access

39. Virtual Private Network(VPN) • Users connect through to PSTN via dialup or another access method • User establishes connection with her organization’s Network Access Server using VPN client-side software and provides A/A credentials • Uses tunneling protocols (such as PPTP, L2TP) to encapsulate data before sent across PSTN

40. Virtual Private Network(VPN) • Secure connection established over the Internet via PPTP Connection established between remote host and NAS / VPN server Data are encapsulated

41. Virtual Private Network(VPN) • Great!! – low cost + secure – why wouldn’t you do this? • Design and implementation is extremely complex • Reliability can be an issue and depends on the network provider • Higher QoS higher $$ • As you scale up, compatibility issues may arise • Security issues if wireless is employed

42. Dialup (modem) with PSTN • Digital signal from PC converted to analog signal for transmission over phone lines by modem • Used for dial-up Internet connections and some WAN technologies • http://www.dialupsound.com/ • Why are dialup modems so slow?

43. Digital Subscriber Line (DSL) • Network connection technology that uses standard telephone lines, but achieves greater speeds than dialup • Supports multiple voice, data, and video channels over a single line • How is this possible?

44. Digital Subscriber Line (DSL) • Services running at different down/up stream speeds are referred to as Asymmetric • Services running at same down/up stream speeds are referred to as Symmetric • Why might there be a difference here?

45. Cable TV Internet (CATV) • Cable company solution to high-speed Internet access • Here, we discuss a CATV modem, which uses same physical cable as TV • See for interesting discussion on differences between modem, Netflix, Google TV http://www.pcmag.com/encyclopedia/term/39164/cable-internet

46. Cable TV Networks (CATV) • Higher bandwidth than dialup but not necessarily higher than DSL – depends on service provider and how much you are willing to pay • Asymmetric service • Sharedtechnology - you are essentially sharing the network bandwidth with your neighbors • DSL and dialup are dedicated connections

47. Network Standards and Protocols • Protocol - a formal set of steps and rules that specifies the format of data as well as the rules to be followed during transmission (TCP, IP, HTTP, DHCP, …) • Standard – agreed upon sets of guidelines and definitions to allow different products and services from different manufacturers to work together (ANSI SQL, IEEE 802.3,…)

48. Network Protocols • Computers use MANY protocols even during simple data exchanges • Enable communication between • Different computers • Different hardware within the computer • Different software within the computer • Hardware and software within the computer • Protocols specify how communication occurs and the form it takes

49. Network Protocols • Transmission control protocol/Internet protocol (TCP/IP) - Provides the technical foundation for the internet as well as for large numbers of private networks • Referred to as the “Internet Protocol Stack” • There are many more protocols that comprise the TCP/IP stack – these are the foundational protocols • All protocols have different “jobs”

50. Network Protocols • Internet Protocol (IP) • Provides a generic address understood by all devices on the Internet • Independent of specific networking technologies • Routes all IP datagrams independently • No guarantee that packets will travel on same route to destination • Allows for fragmentation and reassembly of datagrams • Can subdivide datagrams to fit in any frame payload