CIS 3230 Exam 2, Chapter 4 and 5 Business Data Communications & Networking Quiz reveiw

Burst Error

1 data bit is changed by the error-causing condition. Normally errors appear in bursts

Parity Check

1-bit check value Based on the number of ones in a message. Even 1's - Even parity Odd 1's - Odd parity Detects 50% of errors.

CheckSum

1-byte (typically) check value Checksum algorithms vary in the creation of check values Detects 95% of errors

Transport Layer Functions

1. Linking to the application layer (TCP/UDP may serve multiple application layer protocols) 2. Segmenting (Breaking up large files into smaller segments 'and putting them back together') 3. Session management(A session can be thought of as a conversation between two computers or creating a virtual circuit)

Stop & Wait ARQ

1. Receiver receives frame and sends: -Acknowledgement (ACK) if no error -Negative acknowledgement (NAK) if error 2. If NAK, sender re-sends data 3. If no ACK or NAK, Sender retransmits frame after "timeout" 4. If no ACK, sender re-sends data, receiver sends ACK and deletes duplicate frame

Sources of Network Errors

Line Noise and Distortion Extra bits "Flipped" bits Missing bits

Primary Jobs of the Network Layer

Logical Addressing Routing Encapsulation Fragmentation and Re-assembly Error Handling

Attenuation

Loss of power a signal suffers as it travels from the transmitting computer to the receiving computer

Addressing

Used to direct messages from source to destination Addresses may be translated (resolved) from one layer to another

Transmission Efficiency Calculation

(# 𝑜𝑓 𝑖𝑛𝑓𝑜𝑟𝑚𝑎𝑡𝑖𝑜𝑛 𝑏𝑖𝑡𝑠 (𝑜𝑟 𝑏𝑦𝑡𝑒𝑠))/(# 𝑜𝑓 𝑖𝑛𝑓𝑜𝑟𝑚𝑎𝑡𝑖𝑜𝑛+𝑜𝑣𝑒𝑟ℎ𝑒𝑎𝑑 𝑏𝑖𝑡𝑠 (𝑜𝑟 𝑏𝑦𝑡𝑒𝑠)) Async Effiency = 8/(8+3) = 0.73 = 73%

Error Correction Techniques

* Retransmission (Backward error detection) * Automatic Repeat reQuest (ARQ) (stop & wait, continuous) * Forward Error Detection-Receiving device can correct messages without retransmission.

Media Access Control (MAC)

Controls the physical hardware; Controls how and when the physical layer converts bits into the physical symbols that are sent down the circuit.

IPv4 addresses are ___ bits

32 10000001 , 01001111 , 01001110 , 11000001

ICMP (Internet Control Message Protocol)

A core protocol in the TCP/IP suite that notifies the sender that something has gone wrong in the transmission process and that packets were not delivered.

Enhanced Interior Gateway Routing Protocol (EIGRP)

A dynamic link state protocol (developed by Cisco) Records transmission capacity, delay time, reliability and load for all paths

Media Access Control

Controls which device transmits data and when. Controlled Access Contention Access

Synchronous transmission

All the letters or data in one group of data are transmitted at one time as a block of data. The block of data is called a frame.

Dynamic Routing

Allows a router to determine the best route between two nodes automatically and then store this information in a routing table. makes automatic adjustments of the routes according to the current state of the route in the routing table. Dynamic routing uses protocols to discover network destinations and the routes to reach them. RIP and OSPF are the best examples of dynamic routing protocols. Automatic adjustments will be made to reach the network destination if one route goes down. Easy to configure. More effective at selecting the best route to a destination remote network and also for discovering remote network.

Static Routing

An type of routing used by a network administrator to manually specify the mappings in the routing table. Static routing is a process in which we have to manually add routes to the routing table. It adds security because an only administrator can allow routing to particular networks only. No bandwidth usage between routers.

Logical Addressing

As opposed to physical addressing, the process of assigning organized blocks of logically associated network addresses to create smaller manageable networks called subnets. IP addresses are one example of logical addressing. Systems communicating with each other must have an IP address (4 or 6) which is assigned by a DHCP server Network layer uses the IP addresses which can change, but data link layer uses MAC addresses, which can not be changed, and are assigned by the NIC

Dynamic addressing

Assigning addresses permanently can be inefficient when devices are not connected to network A server can supply IP addresses automatically

Network Errors

Corrupted Data, Lost Data

Point-to-point protocol (PPP)

Common WAN protocol used to establish a direct connection between two nodes

Controlled Access

Common in wireless LANs Access Request Each device must get "permission" to transmit, similar to raising a hand

Synchronous transmission

Data sent in a large block called a frame Includes addressing information Includes synchronization characters to let the receiver know when data transmission begins

Required network addressing information:

Device's own IP address Subnet mask IP address of default gateway (most commonly the router) IP address of at least one DNS server

Dynamic routing algorithms

Distance Vector Link State

Border Gateway Protocol (BGP)

Dynamic distance vector protocol used for exterior routing

Routing Information Protocol (RIP)

Dynamic distance vector protocol used for interior routing

Open Shortest Path First (OSPF)

Dynamic link state protocol used for interior routing Selects the best trip based on network traffic and error rates.

Sessions provide reliable ____________________connections

End-to-end

Ethernet standard IEEE 802.3

Ethernet is a very popular LAN protocol that has been further refined and developed into a formal standard called IEEE 802.3ac

What does the Trailer consist of?

FCS (Frame Check Sequence) and Stop Frame (When length field is not used in Header)

Static Routing

Fixed routing tables ALL computers or routers in the network make their own routing decisions following a formal routing protocol.

How are messages broken down for transport?

Fragmentation and Re-assembly

Data Link Layer: Frames are given a

Header and Trailer

How can we increase efficiency?

Increase Data bits Decrease Overhead bits

Error Handling

ICMP is used to send error messages It is a layer 3 (network layer) protocol Used only for feedback purposes Example of ICMP: ping and traceroute

Internet Protocol (IP) types

IPv4: 32-bit addresses IPv6: 128-bit addresses

Foreword error correction.

Includes a certain level of redundancy in transmitted data so that receiving device can correct errors Does not require retransmission

Major functions of a data link layer protocol

Media Access Control Error Control Message Delineation

Protocols

Message Delineation Ethernet PPP Transmission Efficiency

Protocols differ by

Message delineation Frame length Frame field structure

Throughput

More complicated than simple protocol efficiency because it depends on the retransmission rate, transmission rate, and delay

Dynamic Host Configuration Protocol (DHCP)

Most common protocol for dynamic addressing Device sends out broadcast message DHCP responds with IP settings

Transmission Control Protocol (TCP)

Most common transport layer protocol PDU called a segment Used for reliable transmission of data 160 - 192 bits (20 -24 bytes) of overhead

Asynchronous serial transmission (async)

Old protocol (e.g., used in teletype) Transmits one character at a time Delineation indicated by start and stop bits

User Datagram Protocol (UDP)

Operates at the transport layer PDU called a segment Used in time-sensitive situations, for control messages, or when reliability is handled by the application layer 32-64 bits (4-8 bytes) of overhead

TCP/IP

Originally developed as a single internetworking protocol by Vint Cerf and Bob Kahn in 1974 Most common protocols of the Internet and in LANs, WANs, and backbone networks

Error Control

Prevent Detect Correct

Impulse Noise

Primary source of errors in data communications. (Click or crackling noise)

Routing

Process of identifying what path to have a packet take through a network from sender to receiver.

Asynchronous transmission

Referred to as start-stop transmission because the transmitting computer can transmit a character whenever it is convenient, and the receiving computer will accept that character.

Polling

Roll-call polling- Central device (controller) determines which devices can transmit Each client is checked periodically to see if it needs to transmit Hub Polling (token passing)- One device begins the poll and then passes it to another device until it reaches them all

Dynamic Routing

Routing decisions are made in a decentralized manner by individual computers. Multiple routes through the network, searching for the best route.

Default Routing

Routing method that is used to send packets with a remote destination network that is not located in the routing table of the next-hop router the router is configured to send all packets towards a single router (next hop). It doesn't matter to which network the packet belongs, it is forwarded out to the router which is configured for default routing. It is generally used with stub routers. A stub router is a router that has only one route to reach all other networks.

TCP connections are opened using a three-way handshake

SYN SYN-ACK ACK

What does the Header consist of?

Start Frame, Address, and Type/Length

What are the types of Routing Approaches?

Static, Default, and Dynamic Routing

FCS (Frame Check Sequence)

The field in a frame responsible for ensuring that data carried by the frame arrives intact. It uses an algorithm, such as CRC, to accomplish this verification.

Synchronous Data Link Control (SDLC)

Synchronous bit-oriented protocol developed by IBM Uses bit stuffing (zero insertion) to overcome transparency problem

Routing

Takes information from the transport layer to add a header before sending to data link layer Once layer 3 header is created, it is sent to data link layer which is called encapsulation. Layer 3 (network layer) header contains the source and destination for the data being encapsulated

Parity checks

Technically used for 1 bit error detection. Can also detect any odd number of bit errors. Involves adding an extra "parity" bit to the bit string For even parity, make the total number of 1's in the bit string an even number. This mechanism decides the value of the parity bit. Odd parity makes the number of 1s odd instead of even.

IPv4

The Internet Protocol version 4 is the dominant protocol for routing traffic on the Internet, specifying "to" and "from" addresses using a dotted decimal such as "122.45.255.0". Most common 32 bits (4 octets) Up to 4.19 billion addresses available, but we will eventually run out of them...

IPv6

The Internet Protocol version 6 provides a large number of new addresses to route Internet traffic, using "from" and "to" addresses written as colon-hexadecimal notation, such as "fe80::42:acff:feaa:1bf0". We will eventually move to IPV6 from IPV4 128 bits (8 groups of hex digits) Up to 2^128 addresses available Provides 4.8 x 10^28 addresses per person, while IPV4 provides less than 1 IP address per person

Network Layer

The third layer in the OSI model. Protocols in this layer translate network addresses into their physical counterparts and decide how to route data from the sender to the receiver.

Describe the Data Link Layer

This layer defines the rules that determine when a device can send data over a particular medium. Data link protocols also define the format of a header and trailer that allows devices attached to the medium to successfully send and receive data. Lies in between the Network layer and the Physical layer To provide communication across physical media Communication between two NIC (network interface cards) Connects upper layer processes to the physical layer Network layer packets don't have a way to cross physical median Data link layer formats network layer data packets into frames, and send them throughout the network Receives data from network layer, transforms it into frames, pushes it to the actual network. Provides data delivery between ethernet devices Has two sub layers: Mac layer LLC layer

Fragmentation and Re-Assembly

This occurs if the data in the header is too large (over 1500 bytes) for the maximum frame size handled by the data link layer Network layer will divide the packet into multiple fragments and sends each individual fragment that is the correct size to the data link layer. These fragments are reassembled upon the arrival to the destination layer

Address resolution

Translate host name to IP address www.indiana.edu → 129.79.78.193

Domain Name Service (DNS)

Translates an Internet Address such as www.yahoo.com into an IP address such as 204.71.200.74

Contention Access

Transmit whenever circuit is available with no centralized control Devices must be "polite" and follow these steps: *"Listen" for traffic *If another device is transmitting, wait to transmit *Otherwise, transmit (and keep listening) *If another device begins to transmit, stop and wait

Cyclic redundancy check (CRC

Treats message as a single binary number Divides by a preset number Uses remainder as the check value

Encapsulation

When data link layer takes the header created by the network layer, it turns it into a frame (maximum of 1500 bytes) which is called encapsulation.

Sources of Errors

White Noise Impulse Noise Cross-Talk Echo Attenuation Intermodulation Noise

Parity Checks are

a check used to see if data was correctly transmitted according to the even or odd agreed-upon parity transmission convention

Line Noise

a power flaw, is a fluctuation in voltage levels caused by other devices on the network.

Centralized Routing

all routing decisions are made by one computer or router

Single parity check

cannot detect burst errors A burst error is as likely to cause an even number of errors as an odd number of errors Burst errors cause errors in a sub-string of arbitrary length

Transmission Rate of Information Bits (TRIB)

is a measure of the effective # of bits transmitted in a unit of time

Crosstalk

occurs when the signals of one wire affect the signals on an adjacent wire. Crosstalk occurs when one circuit picks up signals in another (hearing other conversations in the background when on the phone)

Multicast

one computer to a group of computers (e.g., videoconference)

Broadcast

one computer to all computers in the network

Unicast

one computer to another computer

Server Name Resolution

the translation of application layer addresses into IP addresses. Done using the Domain Name Server (DNS)