Week 01: Basic Concepts PDF

Week 01: Basic Concepts Learning Goals: By the end of class you should be able to… List the 5 components of data communication Distinguish between simplex, half duplex, and full duplex Define a network and identify some of the key componen...

Week 01: Basic Concepts Learning Goals: By the end of class you should be able to… List the 5 components of data communication Distinguish between simplex, half duplex, and full duplex Define a network and identify some of the key components of a network Define LAN, WAN, MAN, PAN Identify mesh, star, ring, hybrid topologies and advantages/disadvantages of each Distinguish between point to point and point to multipoint Distinguish between packet switched and network switch networks Identify major standardizations bodies (ANSI, IEEE, etc…)  Data Flow Simplex (computer monitor) Half-duplex (walkie talkie) Full-duplex ( telephone)  What are the necessary components of communication?  Components of Data Communication 5 Components of Data Communication – Mem Acronym TRaMPS 1. Sender 2. Receiver 3. Message 4. Transmission media 5. Protocol  Network A network is the interconnection of a set of devices capable of communication Made up of: – Nodes – Links – Interfaces  Network: Nodes Nodes – End nodes: PC, servers, smart phones – Connecting (networking) nodes: Modems, Switches, Access Points, Routers  Features of Network Network criteria – Performance Throughput Delay – Reliability – Security Physical structure Physical Topology Types of Connection Network Types  Network Types What is the difference between each of the following? – Local Area Network (LAN) – Wide Area Network (WAN) – Metropolitan Area Network (MAN) – Personal Area Network (PAN)  LAN A Local Area Network (LAN) is usually privately owned and connects some hosts in a single office, building, or campus Depending on the needs of an organization, – A LAN can be as simple as two PCs and a printer in someone’s home office, or – It can extend throughout a company and include audio and video devices  LAN Each host in a LAN has an identifier, an address, that uniquely defines the host in the LAN A packet sent by a host to another host carries both the source host’s and the destination host’s addresses  Comparison Table LAN MAN WAN PAN 1. LAN stands for Local 1. MAN stands for 1. WAN stands for 1. PAN stands for Area Network. Metropolitan Area Wide Area Network. Personal Area Network. Network 2. Limited in Size 2. A MAN is optimized 2. Its long distance 2. Covers small for a large geographical communications. distances area than LAN. (usually a Usually wider than a usually a room few blocks) MAN (ambiguous) (Bluetooth, e.g. The Internet USB) 3. Privately owned and 3. Owned by businesses operated leased by customers 4. Point to point or 4. Usually only point to point to multipoint point 5. Connects host like 5. Usually connects PCs and Servers networking devices like switches and routers  WAN Links Point-to-point WAN link Switched WAN  A Practical Examples of Interconnection An internetwork made of two LANs and one WAN Heterogeneous Network Made of WANs and LANs  Point to Point/ Point to Multi-point Connections Examples of each? Point to Point  Multipoint Multipoint (point-to-multipoint) link, shared links  Point to Point/ Point to Multi-point Connections The difference between point to point and point to multipoint connections is… Network Topology  Physical Topology Physical Topology refers to the way in which a network is laid out physically Four basic topologies – Mesh – Star – Bus – Ring  Mesh Topology Full mesh – Each node is connected to every other node – Very reliable, but – Quite expensive If there are n nodes in the network, we need: (i) n(n-1)/2 links (ii) n(n-1) interfaces n=5 Partial mesh # of links = # of interfaces =  Star Topology Each is connected to a (hub) node with – Point-to-point links – No connection between end nodes  Bus Topology Each end-node is connected to – A backbone cable – Using multipoint links Not used in modern networks  Ring Topology Networking nodes daisy-chained connection using – Point-to-point link End nodes are connected to networking nodes get the data on the ring Used in Optical Fibre network in WANs  Hybrid Topology Combination of more than one basic topology More practical Hybrid topology is always an extended star Packet Switching  Switching An internet is a switched network in which a switch connects at least two links together A switch needs to forward data from a network to another network when required The two most common types of switched networks are: – Circuit-Switched (CS) network – Packet Switched (PS) network Circuit-Switched (CS) Network Packet-Switched (PS) Network  Difference between Circuit and Packet Switched Network Circuit switch maintain a connection, all data follows the same path throughout the communication (can waste bandwidth – even if no data being sent there is an established connection) - telephone call Packet switching data can follow any path it wants to go from source to destination (field trip to the CN tower) Networking Standards Standardization Bodies  Internet Standards An is a thoroughly tested specification that is useful to and adhered to by those who work with the Internet – It is a formalized regulation that must be followed (IETF) makes the internet standard, and they are one of two sub- organizations of the Internet Society Internet draft – Initial document RFC- Request for Comment – Working protocols are already there Standard – Formal ‘Standard’ status Internet Internet RFC Draft Standard  Standardization Bodies International – International Organization for Standardization (ISO) – International Telecommunication Union (ITU) – International Electrotechnical Commission (IEC) – … Regional – ETSI (Europe) Country – Standards Council of Canada (SCC) – American National Standards Institute (ANSI) Other – IEEE, IETF, W3C  ISO International Organization for Standardization Collection of organization standards representing 146+ countries Goal is to establish international technological standards to facilitate global exchange of information and barrier-free trade Fewer than 300 of ISO’s more than 14,250 standards apply to computer-related products and functions Most famous for developing the Open Standard Interconnect Model (OSI)  ITU International Telecommunication Union Regulates international telecommunications: – Radio and TV frequencies – Satellite and telephony specifications – Networking infrastructure – Tariffs applied to global communications Typically, documents pertain more to global telecommunications issues than to industry technical specifications  IEEE Institute of Electrical and Electronics Engineers International society composed of engineering professionals Goals are to promote development and education in electrical engineering and computer science IEEE technical papers and standards (Project 802) are highly respected in the networking profession – Can purchase IEEE documents online from IEEE’s Web site (www.ieee.org)  Standards Council of Canada (SCC) Federal Crown corporation Promote efficient and effective voluntary standardization in Canada, where standardization is not expressly provided for by law Does not develop standards directly – Helps other organizations to develop or participate in international standards Represents Canada in international standardization – E.g in ISO and IEC Web: http://www.scc.ca/  ANSI American National Standards Institute (ANSI) – Composed of more than a thousand representatives from industry and government – Represents United States in setting international standards ANSI standards documents available: – ANSI’s Web site (www.ansi.org) – At university or public libraries  EIA and TIA Electronic Industries Alliance (EIA): – Trade organization composed of representatives from electronics manufacturing firms across US – Sets standards for its members – Helps write ANSI standards – Lobbies for legislation favorable to growth of computer and electronics industries Telecommunications Industry Association (TIA): – Focuses on standards for information technology (IT), wireless, satellite, fiber optics, and telephone equipment  ISOC Internet Society Professional membership society that helps to establish technical standards for the Internet Oversees groups with specific missions: – Internet Architecture Board (IAB): Technical advisory group of researchers and professionals Interested in overseeing Internet’s design and management – Internet Engineering Task Force (IETF): Sets standards for how systems communicate over the Internet How protocols operate and interact  IANA and ICANN Internet Protocol (IP) addresses – Addresses used to identify computers on the Internet and other TCP/IP-based networks Internet Assigned Numbers Authority (IANA): Used to keep records of available and reserved IP addresses and determines how addresses were doled out – In 1997, coordinated efforts with three Regional Internet Registries (RIRs) Not-for-profit agency that manages distribution of IP addresses to private and public entities – In late 1990s U.S. Department of Commerce (DOC) overhauled IP addressing and domain name management Internet Corporation for Assigned Names and Numbers (ICANN): Ultimately responsible for IP addressing and domain name management – IANA still performs system administration – Individuals and businesses lease addresses from Internet Service Provider (ISP) Business providing access to Internet and other services  World Wide Web Consortium (W3C) Develop web related standards World-wide membership and offices Main standards – HTML – CSS – XML Week 02 Network Models Layered Protocol Architecture  Protocol: What is it? You’ve probably heard the term protocol used a lot A protocol is just a set of rules for how we communicate The English language is even a protocol Syntax, Semantics, and Timing  Protocol Layering When communication is simple, we may need only one simple protocol When the communication is complex, we need a protocol at each layer, known as protocol layering  Protocol Layering: Simple Example In this case communication is so simple we only need one layer for the protocol What would be some rules for communicating in this case though? Protocol Layering: Simple Example However even in this simple case we need some rules… – Maria and Ann should say hello – They should not speak at the same time – Vocabulary should be appropriate for the conversation – Should say goodbye when they leave Protocol Layering: More Complex Postal carrier facility  Protocol Layering: Pros/Cons What are some pros and cons of protocol layering? Postal carrier facility  Protocol Layering: More Complex An advantage of separating the tasks out like this – Flexibility in selecting the machine to do each task (for instance Maria may not need a machine to read/write the message) – Communication in intermediate layers does not always need to use all the layers (see the routers in TCP/IP) – If Maria decides one layer needs to be replaced she needs only replace the machine at that layer It would be “simpler” to handle this in a single layer but if they discover their code is broken they would replace the whole system instead of only one layer  Principles of Protocol Layering 1. Each layer must be capable of performing two opposite tasks to ensure they can communicate 2. The object in each layer should be identical (in the case of tcp/ip frame, datagram, etc…)  Logical Connections Each layer does not *actually* communicate with each other instead we imagine that they do with logical connections Layers and Protocols (NOT the same!) Layer m on one computer logically communicates with layer m on another computer The rules and conventions used in this communication are collectively known as the layer m protocol TCP/IP Model  TCP/IP Protocol Suite Group of communication protocols used by the internet It is commonly known as TCP/IP, because its most important protocols, the Transmission Control Protocol (TCP) and the Internet Protocol (IP), were the first networking protocols defined in this standard It is occasionally known as the DoD model (department of defense), because the development of the networking model was funded by DARPA, an agency of the United States Department of Defense  TCP/IP Protocol Suite TCP/IP provides End-to-End Connectivity specifying how data should be – Formatted – Addressed – Transmitted – Routed, and – Received at the destination – Memory Acronym: FARTAR TCP/IP organizes this into 5 layers  TCP/IP Protocol Layers It may be helpful to think of this as an assembly line (just like our activity)  Logical Connections in TCP/IP What’s the difference in the connection between the layers? – A,T, N are end to end (they run from host to host) – D and P are hop to hop (they only worry about delivery of a message from node to node) – Activity: Memory Acronym for ATNDP  Application Layer The application layer provides services to the user it acts as a bridge between the software that is used and lower layer network protocols Some examples include HTTP (used to view the internet), SMTP which is used in email, FTP which is used to transfer files  Transport Layer End to end protocol which acts as a liaison between a client program and a server program Main protocol at this layer is TCP and it establishes a logical connection and provides flow control, error correction, and congestion control Other main protocol is UDP which does not require a connection, and no error correction  Network Layer Responsible for creating a connection between the source computer and the destination computer and moving the packets over the internet Each router along the path is responsible for choosing the best path for the data to take  Data Link Layer The Data Link Layer is responsible for taking the frames and moving it from one node to the next (within the network) TCP/IP does not specify which protocol needs to be used. Some protocols provide complete error detection, others do not  Physical Layer Responsible for carrying the bits in a frame across the link (there is another “hidden” layer so the physical layers do not directly communicate - the transmission media) Layered Architecture Example  Identical Objects in TCP/IP Identical objects (messages) Identical objects (segment or user datagram) Identical objects (packets or datagram) Identical objects (datagram) Identical objects (frame) Identical objects (frame) Identical objects (bits) Identical objects (bits) Note: Switches are not shown as they do not change data objects. At network layer, ‘datagram’ is more commonly called ‘packet’.  Summary of TCP/IP layers Layer Function Data Object Application Messages Transport Segment/ User Datagram Network Packets/Datagram Data Link Frame Physical Bits  Major Protocols in TCP/IP TCP/IP Model Layers Application HTTP SMTP POP3 SNMP FTP DNS DHCP Transport TCP UDP SCTP Network ICMP IPv6 IP ARP RARP Data Link Ethernet IEEE 802.11 (WiFi) STP PPP VLAN Physical Ethernet PHY (100BaseTX, …) WiFi PHY (802.11a, b, g, n, ac) SONET/SDH  Relationship between Layers/Addresses Addresses Example Protocol TCP/IP Model Layers Application Applications layer Protocols Specific addresses (HTTP, FTP, DNS, …) Application Port number TCP UDP Transport IP address IP IPv6 Network Physical address Network Access Protocols Data Link (MAC address) (Ethernet, WiFi, …) Physical OSI Model  OSI Reference Model Another suite of protocols established by ISO (International Organization for Standards) Open Systems Interconnection model was first introduced in the1970s and consisted of seven layers Questions: – What is an open system? – Why is the OSI model not used? OSI vs. TCP/IP  OSI vs. TCP/IP 1. The TCP/IP suite was already well established 2. Some layers in the OSI model were never fully developed 3. The OSI level did not offer a high enough level of performance to entice people to switch from TCP/IP Encapsulation Encapsulation/Decapsulation  Encapsulation/Decapsulation Essentially encapsulation is the process of adding headers to the message and decapsulation is the process of removing or unwrapping the original message  Encapsulation/Decapsulation Application Layer: Message Transport Layer: adds identifiers of the source and destination applications and information that is needed for end to end delivery for the segment Network Layer: adds identifiers of the source and destination host as well as error checking for the datagram/packet Data Link Layer: adds identifiers for the next hop (node) that the frame will travel Addressing  Addressing Another concept related to protocol layering in the Internet, addressing Any communication that involves two parties needs two addresses: – Source address – Destination address Note: Although it looks as if we need five pairs of addresses, one pair per layer, we normally have only four because the physical layer does not need addresses; the unit of data exchange at the physical layer is a bit, which definitely cannot have an address.  Physical Data Units (PDU) and Addresses in TCP/IP PDU Memory Acronym: Big Fat Pigs Smell Layer PDU Address Application layer Message Name / Application specific Transport layer Segment / User Port number datagram Network layer Datagram / Packet Logical address/ IP address Data Link layer Frame MAC address (also called physical address) Physical layer Bit N/A  Multiplexing/Demultiplexing – Multiplexing in this case means that a protocol at a layer can encapsulate a packet from several next-higher layer protocols (one at a time) – Demultiplexing means that a protocol can decapsulate and deliver a packet to several next-higher layer protocols (one at a time) Week 03 Protocol Stack Protocol Stack in Operating System  Learning Goals: By the end of class students should be able to … Explain what an API is and its relation to sockets as well as the benefits of this system Distinguish between user, kernel and device areas as well as the difference between the host area and device area Explain the importance of checksum and ARP Discuss briefly the process involved in receiving data and transmitting data Define Winsock and explain its importance to networking  Last Week: We discussed TCP/IP What were the layers? What were the PDUs (physical data units)? Next question: How is TCP/IP implemented in different operating systems?  Protocol Stack Application Refers to implementation of TCP/IP protocols in operating Socket API system TCP/IP Library in OS – How software modules for protocols are arranged layer by Device Drivers layer – How API calls are chained (passed down) Devices  What is an API? (Application Programming Interface ) An API is a set of instructions for how the application layer communicates with the network layer The processes running at the application layer are able to communicate over the internet There are several different APIs: socket interface, transport layer interface and STREAM Delivery Service  What is a Socket? What would be an advantage to this system? – We can use the same programming/instructions to write and read from sockets that we do for other devices and files  Sockets (aside) Every process on a machine assigned a port number 0 to 65535 Process’s port number plus host machine’s IP address equals process’s socket – Ensures data transmitted to correct application Well Known Ports: in range 0 to 1023 – Assigned to processes that only the OS or system administrator can access  Sockets (aside) Registered Ports: in range 1024 to 49151 – Accessible to network users and processes that do not have special administrative privileges Dynamic and/or Private Ports: in range 49152 through 65535 – Open for use without restriction Socket Number: Port Number and IP address together Areas within an OS for Protocol Layers User area User User Applications Kernel area File Device area Sockets Host TCP Kernel IP Ethernet Device drive Network Interface Device Device Card (LAN card) Areas within an OS for Protocol Layers What’s the difference User User Applications between user area, File kernel area, and device area? What Host Sockets do they mean? Kernel TCP IP Ethernet What’s the difference Device drive between host and device? Device Network Interface Device Card (LAN card) Areas within an OS for Protocol Layers Tasks at the user area and the kernel area are performed by the CPU. The user area and the kernel area are called "host" to distinguish them from the device area. Kernel space is strictly reserved for running privileged kernel, kernel extensions, and most device drivers. In contrast, user space is the memory area where application software and some drivers execute. (from wikipedia) The term userland (or user space) refers to all code which runs outside the operating system's kernel. (from wikipedia)  Host and Device Host: Implemented in main CPU Device: Implemented in NIC (Network Interface Card) Network Interface Card – Hardware that actually sends and receives frames – Creates signal – Converts between bits and electrical (or other type of ) signal  Data Transmission User User Applications write (fd, buf, length) File Validate file descriptor (fd) Sockets Copy/append buf to socket buffer Create TCP segment according to TCP state. TCP Compute checksum Kernel Add IP header, perform IP routing. IP Compute checksum Add Ethernet header Ethernet Perform ARP Device driver Tell NIC to send the packet (frame) Network Interface Fetch the frame from host memory Device Send it Card (LAN card) Interrupt the host when send is done  Data Transmission What is a checksum? What is ARP?  Data Transmission: Checksum Is a mathematical algorithm which totals all the bits within transmitted data and is used to determine if an error occurred  Data Transmission: ARP Network layer protocol – Obtains MAC (physical) address of host Creates database that maps MAC address to host’s IP (logical) address ARP table or cache: local database containing recognized MAC-to-IP address mappings – Dynamic ARP table entries created when client makes ARP request that cannot be satisfied by data already in ARP table – Static ARP table entries entered manually using ARP utility  Data Receiving User User Applications read (fd, buf, length) File Validate file descriptor (fd) Copy data to user space Sockets Remove it from socket buffer Tell TCP Validate the packet TCP Run TCP protocol Kernel Append payload to socket buffer Validate the packet IP Perform IP routing De-multiplex based on IP ‘protocol’ field Ethernet Validate the packet De-multiplex based on ‘ethertype’ field Validate the frame Device driver Wrap it in OS packet structure Network Interface Validate the frame Device Transfer it to a pre-allocated host memory buffer. Card (LAN card) Interrupt the driver that there is a new packet  Encapsulation/Decapsulation User User Applications  User data  Send socket buffer: File 1st Segment next segments  Sockets TCP- User data TCP Header Kernel IP- TCP- IP Header Header User data Ethernet Eth- IP- TCP- User data Header Header Header Device driver Network Interface Eth- Eth- IP- TCP- Eth- Device Preamble Header Header Header User data CRC Card (LAN card) TCP Header (in depth) IP Header  Winsock Dynamic-link library in Windows (WINSOCK.DLL) Provides a common Application Programming Interface (API) – It is not the TCP/IP implementation itself, just the API Developers use Winsock to network applications that use the Transmission Control Protocol/Internet Protocol (TCP/IP) stack – Programmer who develops a Windows-based TCP/IP application, such as an FTP or Telnet client, can write programs that work with any TCP/IP protocol stack that provides Windows Socket Services (WINSOCK.DLL)  References – Winsock, http://en.wikipedia.org/wiki/Winsock – Description of the WINSOCK.DLL File, http://support.microsoft.com/kb/122928 – Understanding TCP/IP Network Stack & Writing Network Apps, http://www.cubrid.org/blog/dev- platform/understanding-tcp-ip-network-stack/ – Find other sources inline  Week 04 Networking Devices Hubs, Switches, and Routers Oh MY!  Networking Connections: Devices We use connecting devices to connect hosts together to make a network or to connect networks together to make an internet Connecting devices can operate in different layers of the Internet model – Physical Layer (layer 1): Hubs – Data Link Layer (layer 2): Link-layer switches – Network Layer (layer 3): Routers Hubs, Switches, and Routers Today we are going to learn about network devices which are connecting nodes, specifically routers, switches, bridges and hubs. Each of these connecting nodes has characteristics and functions in a network, and each has advantages and disadvantages Note: repeaters do not have any dis/adv for this activity Repeaters and Hubs Repeater: Hardware & Layers  Repeater: Functions Layer 1 devices, which amplify and re-time network signals so LANs can be extended to greater lengths. Can be single-port "in" and single-port "out" devices, though more often now, they are stackable (modular), or multi-port, better known as hubs. They act only on the bit level and look at no other information. Hubs: Hardware and Layers  Hubs: Functions Also known as a multi-port repeater – Amplify and re-time network signals, at the bit level, to a large number of users. – Can increase the number of nodes that can be connected to a network – Typical to see 4, 8, 12, and up to 24, ports on multiport repeaters – Layer 1 devices because they act only on the bit level and look at no other information – Only the intended recipient keeps the data Hubs: Functions Data discarded by unintended recipients Data kept by intended recipient  Hubs: Advantages – Can extend a network’s total distance – Do not seriously affect network performance – Certain repeaters can connect networks using different physical media – Is a fun word to say!  Hubs: Disadvantages – Cannot connect different network architectures, such as Token Ring and Ethernet – Do not reduce network traffic They repeat everything they receive – Do not segment the network – Do not reformat data structures Cannot connect networks that require different types of frames  Hubs: Disadvantages Repeaters do not segment a network – Frames that are broadcast on a given segment may collide Devices that “see” the traffic of other devices are said to be on the same collision domain Bridges Bridge: Hardware & Layers  Bridge: Function Filter traffic on a LAN, to keep local traffic local Makes its decisions based on the MAC address Layer 2 device – Uses Layer 2 processing (MAC) to make the decision whether or not to forward information Bridges are used to segment networks into smaller parts  Transparent Bridges Also called learning bridges – Because they build a table of MAC addresses as they receive frames The bridge uses the source MAC addresses to determine which addresses are on which segments – By determining a frame’s origin, the bridge knows where to send frames in the future Ethernet networks mainly use transparent bridges  Advantages of Bridges Can extend a network by acting as a repeater Can reduce network traffic on a segment by subdividing network communications Increase the available bandwidth to individual nodes because fewer nodes share a collision domain Reduce collisions Some connect networks using different media types and architectures  Disadvantages of Bridges Slower than repeaters and hubs – Extra processing by viewing MAC addresses Forward broadcast frames indiscriminately, so they do not filter broadcast traffic More expensive than repeaters and hubs Switches  Switches: Hardware & Layers Functions of Switches: Learning of MAC address Forwarding of frames Avoiding loops  Switches The purpose of a switch is to concentrate connectivity, while guaranteeing bandwidth Think of the switch as something that is able to combine the connectivity of a hub with the traffic regulation of a bridge on each port It switches data from incoming interfaces (sometimes called ports) to outgoing ports, while providing each interface with full bandwidth. The switch is a Layer 2 device that uses the MAC address to make its switching decisions.  Link Layer Switches Operates in both the physical and the data-link layers – As a physical-layer device, it regenerates the signal it receives – As a link-layer device, the link-layer switch can check the MAC addresses (source and destination) contained in the frame Link Layer Switches  How a Switch Learns See animation  Switches: Advantages increase available network bandwidth Reduce the workload on individual computers Increase network performance Networks experience fewer frame collisions because they create collision domains for each connection (a process called microsegmentation) Connect directly to workstations  Switches: Disadvantages Significantly more expensive than bridges Network connectivity problems can be difficult to trace Broadcast traffic may be troublesome  Routers Routers are the most important traffic-regulating devices on large networks  Routers: Hardware & Layers A router is a three-layer device It operates in all of – Physical layer: creates signal – Data-link: checks MAC address – Network layer: checks IP address Routers: Hardware  Routers: Function Router does routing: – Examines incoming packets – Chooses the best path for them through the network, and then – Switches them to the proper outgoing port Makes path selection decisions based on Layer 3 information – Network addresses (IP address) Can also connect different layer 2 technologies, such as Ethernet, token-ring, and FDDI Connect two or more networks Have become the backbone of the Internet  Routers: Function Main Functions – Connect dissimilar networks – Interpret Layer 3 addressing – Determine best data path – Reroute traffic Optional functions – Filter broadcast transmissions – Enable custom segregation, security – Support simultaneous connectivity – Provide fault tolerance – Monitor network traffic, diagnose problems  Routers: Advantages Can connect different network architectures, such as Ethernet and Token Ring Can choose the best path across an internetwork using dynamic routing techniques Reduce network traffic by creating separate collision domains Reduce network traffic by creating separate broadcast domains  Routers: Disadvantages Only work with routable network protocols; most but not all protocols are routable More expensive than other devices Dynamic router communications (inter-router communication) cause additional network overhead, which results in less bandwidth for user data Slower than other devices because they must analyze a data transmission from the Physical through the Network layer  Definitions Segmentation – The breaking down of a single heavily populated network segment into smaller segments, or collision domains, populated by fewer nodes Segment – Part of a network that is divided logically or physically from the rest of the network When network administrators place too many nodes on the same network segment – Causes the number of collisions to increase  Definitions Broadcast storm When two or more stations engage in the transmission of excessive broadcast traffic Microsegmentation Prevents communications between just two computers from being broadcast to every computer on the network or segment When machines must share a wire and compete for available bandwidth with other machines, they experience Contention Gateways Gateways and Other Multifunction Devices Gateway – Combinations of networking hardware and software Connecting two dissimilar networks – Connect two systems using different formatting, communications protocols, architecture – Repackages information – Reside on servers, microcomputers, connectivity devices, mainframes Popular gateways – E-mail gateway, Internet gateway, LAN gateway, Voice/data gateway, Firewall – Memory Acronym: FLIVE Brief Overview of Signal FYI Communication at the Physical Layer  Analog and Digital Signal What’s the difference between an Analog and a Digital signal?  Analog and Digital Signal FYI Analog Signal: – Continuous in time, continuous in value Digital Signal – Discrete in time, discrete in value Analog Data – Information that is continuous – Example: an analog clock that has hour, minute, and second hands gives information in a continuous form – the movements of the hands are continuous Digital Data – Information that has discrete states – Example: a digital clock that reports the hours and the minutes will change suddenly from 8:05 to 8:06  Properties of a Signal FYI What do each of the following mean? Amplitude Frequency Wavelength Phase  Properties of a Signal FYI Amplitude – Analog wave’s strength Frequency – Number of times amplitude cycles over fixed time period – Measure in hertz (Hz) Wavelength – Distance between corresponding wave cycle points – Inversely proportional to frequency – Expressed in meters or feet Phase – Wave’s progress over time in relationship to fixed point  Example of an Analog Signal FYI Analog data signals – Voltage varies continuously – Properties Amplitude Frequency Wavelength Phase  Example of a Digital Signal Digital signals FYI – Pulses of voltages Positive voltage represents a 1 Zero voltage represents a 0 Binary system – 1s and 0s represent information Bit (binary digit) – Possible values: 1 or 0 – Digital signal pulse  Data Modulation Data relies on digital transmission – Network connection may handle only analog signals Modem – Accomplishes translation – Modulator/demodulator  Modem Data modulation – Technology modifying analog signals – Make data suitable for carrying over communication path  What is a Channel Channel – Distinct communication path between nodes – Separated physically or logically  Throughput and Bandwidth Throughput – LIKE A SPEED LIMIT – Measures amount of data transmitted – During given time period – Capacity or bandwidth – Quantity of bits transmitted per second Bandwidth – LIKE LANES OF TRAFFIC – Measures difference between highest and lowest frequencies medium can transmit – Range of frequencies – Measured in hertz (Hz) Throughput and Bandwidth  Transmission Flaws: Effect of Noise FYI What’s the difference An analog signal distorted by noise and then amplified between an amplifier and a repeater? A digital signal distorted by noise and then repeated  Transmission Flaws FYI What do you think each of the following refers to, why is it an issue? Noise Attenuation Latency Jitter RTT (Round Trip Time )  Transmission Flaws: Latency & Jitter FYI Latency – Delay between signal transmission and receipt Causes – Cable length – Intervening connectivity device Jitter – Variation in latency  RTT (Round Trip Time) & Attenuation FYI RTT (round trip time) – Time for packet to go from sender to receiver, then back from receiver to sender Attenuation – loss of signal strength measured in decibels (dB). – Caused by range interference wire size Connectivity Hardware  Connectors and Media Converters TYPES OF TRANSMISSION MEDIA Coaxial Cable Twisted Pair Cable – UTP – STP Fiber Optic Cable – SMF – MMF WE WILL CONSIDER CHARACTERISTICS AND ADVANTAGES AND DISADVANTAGES OF EACH TYPE  Connectors and Media Converters Connectors – Hardware connecting wire to network device – Specific to particular media type – Affect costs Installing and maintaining network Ease of adding new segments or nodes Technical expertise required to maintain network Media converter – Hardware enabling networks or segments running on different media to interconnect and exchange signals Copper Wire-to-Fiber MediaConverter  Coaxial Cable FYI Central metal core (often copper) – Surrounded by insulator Braided metal shielding (braiding or shield) Outer cover (sheath or jacket)  Coaxial Cable: Pros & Cons High noise resistance FYI Advantage over twisted pair cabling – Carry signals farther before amplifier required Disadvantage over twisted pair cabling – More expensive Hundreds of specifications – RG specification number – Differences: shielding and conducting cores Transmission characteristics  Coaxial Cable FYI F-type connector BNC Connector  Twisted Pair Cable Color-coded insulated copper wire pairs – 0.4 to 0.8 mm diameter – Encased in a plastic sheath  Twisted Pair Cable More wire pair twists per foot – More resistance to cross talk – Higher-quality – More expensive Twist ratio – Twists per meter or foot High twist ratio – Greater attenuation  Twisted Pair Cable Wiring standard specification – TIA/EIA 568 Twisted pair wiring types – Cat (category) 3, 4, 5, 5e, 6, and 6e, Cat 7 – CAT 5 or 6 most often used in modern LANs – The higher the number the greater the data rate  Twisted Pair Cable: Pros & Cons Advantages – Relatively inexpensive – Flexible – Easy installation – Spans significant distance before requiring repeater – Accommodates several different topologies – Handles current faster networking transmission rates  Twisted Pair Cable Two categories – STP (shielded twisted pair) – UTP (unshielded twisted pair)  Unshielded Twisted Pair Cable One or more insulated wire pairs – Encased in plastic sheath – No additional shielding Less expensive, less noise resistance  Unshielded Twisted Pair Cable EIA/TIA standards – Cat 3 (Category 3) – Cat 4 (Category 4) – Cat 5 (Category 5) – Cat 5e (Enhanced Category 5) – Cat 6 (Category 6) – Cat 6e (Enhanced Category 6) – Cat 7 (Category 7) Unshielded Twisted Pair Cable A Cat 5 UTP cable with pairs untwisted  RJ-45 and RJ-11 Connectors RJ-45 (ethernet) and RJ-11 (telephone) Connector – STP and UTP use RJ-45 (Registered Jack 45) – Telephone connections use RJ-11 (Registered Jack 11) – Two methods of inserting UTP twisted pairs into RJ-45 plugs: TIA/EIA 568A and TIA/EIA 568B  Fiber Optic Cable Fiber-optic cable (fiber) – One (or several) glass or plastic fibers at its center (core) Data transmission – Pulsing light sent from laser – LED (light-emitting diode) through central fibers  Fiber Optic Cable FYI Cladding – Layer of glass or plastic surrounding fibers – Different density from glass or plastic in strands – Reflects light back to core Allows fiber to bend Plastic buffer – Outside cladding – Protects cladding and core – Opaque Absorbs any escaping light  Fiber Optic Cable Different varieties – Based on intended use and manufacturer Two categories – Single-mode – Multimode  SMF (Single-Mode Fiber) Uses narrow core (< 10 microns in diameter) – Laser generated light travels over one path: Little reflection – Light does not disperse Accommodates – Highest bandwidths, longest distances – Connects carrier’s two facilities Costs prohibit typical LANs, WANs use  MMF (Multi-Mode Fiber) Uses core with larger diameter than single- mode fiber – Common size: 62.5 microns Laser or LED generated light pulses travel at different angles Common uses – Cables connecting router to a switch – Cables connecting server on network backbone  Fiber Optic: Features Benefits (Advantages) – Extremely high throughput – Very high resistance to noise – Excellent security – Ability to carry signals for much longer distances before requiring repeaters than copper cable – Industry standard for high-speed networking Drawback (DisAdvantages) – More expensive than twisted pair cable – Requires special equipment to splice  Week 05 LAN Protocols IEEE 802 protocol set  What is Project 802? A.) A set of standards created by IEEE which sets the rules for how computers internetwork together B.) A set of standards created by the CSA which ensure Canadian computers can connect to the network C.) A set of standards created by the IEEE which allows equipment from different manufacturers to communicate D.) The sequel to the movie 300. It was a project to see what 802 Spartans were capable of.  IEEE Project 802 In 1985, the Computer Society of the IEEE started a project, called Project 802, to set standards – To enable intercommunication among equipment from a variety of manufacturers – To specify functions of the physical layer and the data-link layer of major LAN protocols The relationship of the 802 Standard to the TCP/IP protocol suite is about layer and protocol implementation, as shown next IEE Standard For LANs  Ethernet Evolution Put the following in order from fastest to slowest 1. Standard Ethernet 2. 10 Gigabit Ethernet 3. Fast Ethernet 4. Gigabit Ethernet  Ethernet Evolution Ethernet LAN was developed in the 1970s by Robert Metcalfe and David Boggs It has gone through four generations – Standard Ethernet (10 Mbps): IEEE 802.3 – Fast Ethernet (100 Mbps): IEEE 802.3u – Gigabit Ethernet (1 Gbps): IEEE 802.3z, or ab – 10 Gigabit Ethernet (10 Gbps): IEEE 802.3ae  Standard Ethernet We refer to the original Ethernet technology with the data rate of 10 Mbps as the Standard Ethernet Although most implementations have moved to other technologies in the Ethernet evolution, there are some features of the Standard Ethernet that have not changed during the evolution Ethernet Frame  Ethernet Frame Preamble: contains 56 bits and allows the system receiving the frame to synch its clock if necessary SFD: Start frame delimiter: defines beginning of frame Address: contains the link layer address Type: the protocol that encapsulated the frame: IP, ARP, OSPF CRC: cyclic redundancy check. If CRC is not zero then the receiver discards the frame LLC and MAC  Ethernet Addressing: What is LLC? The data-link layer is divided into two sub-layers. LLC and MAC. LLC stands for logical link control In Ethernet handles framing, flow control, and error control It makes the MAC layer transparent which allows different LANs to connect  Ethernet Addressing: MAC Each station on an Ethernet network (such as a PC, workstation, or printer) has its own Network Interface Card (NIC) NIC fits inside the station and provides the station with a link-layer address Ethernet address or MAC address is 6 bytes (48 bits) – Normally written in hexadecimal notation, with a colon between the bytes – An example of an Ethernet MAC address: 60-67-20-3A-D2-C4 Implementation of Standard Ethernet Implementation of Standard Ethernet  Access Method Since the network that uses the standard Ethernet protocol is a broadcast network, we need to use an access method to control access to the sharing medium The standard Ethernet chose Carrier Sense Multiple Access with Collision Detection (CSMA/CD) CSMA/CD Mechanism: – Node senses the medium – If no one is transmitting, node can transmit – If someone else is transmitting, node “backs off” and waits for the medium to be free  Collision Domains What happens to the collision domain with the bridge? Let’s say we have 10 Mbps bandwidth how much will each pc actually have?  Collision Domains What happens to the collision domain with the bridge? Let’s say we have 10 Mbps bandwidth how much will each pc actually have? A.) Without bridge each will have 10/2 with each will have 10 B.) Without bridge each will have 10 with each will have 20 C.) Without bridge each will have 10/12 with each will have 10/3 D.) Without bridge each will have 10/12 with each will have 10/4  Switched Ethernet What happens to the collision domain with the switch? Let’s say we have 10 Mbps bandwidth how much will each pc actually have?  Switched Ethernet What happens to the collision domain with the switch? Let’s say we have 10 Mbps bandwidth per interface how much will each pc actually have? A.) 10 Mbps B.) 5 Mbps C.) 7 Mbps D.) 20 Mbps  Full-duplex Switched Ethernet No need for CSMA/CD. Why? In this case there is no risk for collision which makes the MAC layers job much easier  Fast Ethernet The goals of Fast Ethernet were to: – Upgrade the data range to 100 Mbps – Be compatible with Standard Ethernet – Keeps the same48-bit address – Same frame format Added autonegotiation: allows a station or hub to negotiate the mode or data range of operation Specified topology: 3 or more stations must be connected in a star with a hub/switch Encoding: see next slide- certain wires must be used to handle the data rate transfer Fast Ethernet  Gigabit Ethernet 1 Gbps speed Compatible with earlier Ethernet standards Initially implemented in fibre optic cable (IEEE 802.3z) Now available in copper media (IEEE802.3ab)  10Gbit Ethernet The IEEE committee created 10 Gigabit Ethernet and called it Standard 802.3ae Fibre optic media Can be used for both LAN and MAN Operates only in Full-duplex – No contention Virtual LANs  VLANs A station is considered part of a LAN if it physically belongs to that LAN The criterion of membership is geographic What happens if we need a virtual connection between two stations belonging to two different physical LANs? We can roughly define a virtual local area network (VLAN) as a local area network configured by software, not by physical wiring VLANs (virtual local area networks) – Logically separate networks within networks Groups ports into broadcast domain Switch Connecting 3 LANs A Switch Using VLAN Software 2 Switches in a Backbone using VLAN A Simple VLAN Design  Advantages of VLANs Flexible – Ports from multiple switches or segments – Use any end node type Reasons for using VLAN – Separating user groups – Isolating connections – Identifying priority device groups – Grouping legacy protocol devices STP (Spanning Tree Protocol) Loop Problem in a Learning Switch Loop Problem in a Learning Switch Although multiple switches create loops in the topology they also ensure reliability (as there is another path in the network ) To solve this problem IEEE specifies STP be used so that a spanning tree containing no loops is created Here is an excellent video on STP  STP (Spanning Tree Protocol) IEEE standard 802.1D Operates in Data Link layer Prevents traffic loops – Calculating paths avoiding potential loops – Artificially blocking links completing loop Three steps – Select root bridge based on Bridge ID – Examine possible paths between network bridge and root bridge – Disables links not part of shortest path Network of Multiple LAN segments with Redundant Connections Every switch has a built in ID. (normally the serial number). The switch with the smallest ID is selected as the root. For us that is Switch 1 (we will pretend, no way to tell from picture)  STP (Spanning Tree Protocol) This is Djikstra’s algorithm – Finds the shortest path between any two nodes You won’t need to know how to do this on the midterm…but you will need to know what algorithm is used Forward and Blocking Ports after using STP Algorithm