327_Midterm

• Bits can be corrupted or destroyed

• Entire packets can be lost

• Packets can be duplicated

• Packets can be delivered out of order

• Multiple computers on a network

• Multiple applications on a computer

• Multiple copies of a single application on a computer

A set of protocols that are designed to work together so that each protocol solves a small part of the communications problem

Protocol suites and Protocol families

A way to deal with complexity by adding multiple levels of abstraction where each level encapsulates some key functionality and exports an interface to other components'

We can delegate the problem or Air Travel Organization into the following layers -

• ticket

• baggage

• gate

• takeoff/landing

• airplane routing

• where each layer implements a service via its own internal actions and relying on the services provided in the layer below. is implemented

Various physical mediums (e.g. departure/arrival airports, intermediate air traffic controllers) can implement some of all of the layers from the bottom-up to solve their specific iteration of the problem

Each layer relies on services from layer below and exports its own services to the layer above

• Simplifies design and implementation

• Easy to modify/evolve

Application, Hardware (maybe all?)

No (False)

Physical:

• Handles the transmission of raw bits over a communication link.

Data Link (Media Access):

• Collects a stream of bits into a larger aggregate called a frame

• Network adaptor along with device driver in OS implement the protocol in this layer

• Frames are actually delivered to hosts based on MAC address.

Network:

• Handles routing among nodes within a packet-switched network

• Unit of data exchanged between nodes in this layer is called a packet

• Packets are actually delivered to hosts based on IP address.

Transport:

• Implements a process-to-process channel

• Unit of data exchanges in this layer is called a message

Session:

Provides the mechanism for opening, closing and managing a communication session between end-user application processes.

Presentation:

Concerned about the format of data exchanged between peers

Application:

Ensures application programs communication with other application programs over a network.

Application:

• Everything else (i.e., how one application uses the Internet)

• Similar to OSI Layer 6 and 7

• Unit of data exchanges in this layer is called a message

Transport (TCP/UDP)

• Specifies how to provide reliable transfer from one application on one computer to an application on another

• Similar to OSI Layer 4

• Unit of data exchanges in this layer is called a segment

Internet (IP)

• Format of packets

• Mechanisms for forwarding packets

• Unit of data exchanged between nodes in this layer is called a datagram

• Not in the OSI Model

Physical:

• Basic network hardware

• Similar to OSI Layer 1

Network Interface:

• MAC frame format

• MAC addressing

• Interface between computer and the network (i.e., the NIC)

• Similar to OSI Layer 2

They are the same

172.32.0.0

A packet switched network

Hub, Repeater

When two devices in the network send data at the same time

Switches

Traceroute

The host machine

14 bytes total:

• Source MAC addresses - 6 bytes

• Destination MAC address - 6 Bytes

• Type field - 2 bytes

• [Optional] a single IEEE standard tag (either 802.1Q or 802.1ad)

• Broadcast domains: 2

• Collision domains: 7

Explanation: For the collision domains, we have 5 computers and one port for E1 so we have 6 collision domains total because we use a switch in the Production Department so 5 are created there, plus one collision domain for the entire Sales department because a hub is being used.

Each of the subnet masks should be set to 255.255.255.0

(CABLES/CABLE TYPE ARE IRRELEVANT IN THIS SETUP)

The IP address of the PC (192.168.11.2/24) is not on the same network as its gateway 192.168.1.1

Network Bridges

10.188.31.0/27

Router

MAC address table

Packer capture (NOT encapsulation)

Encapsulation is a process by which a lower-layer protocol receives data from a higher-layer protocol and then places the data into the data portion of its frame. Thus, encapsulation is the process of enclosing one type of packet using another type of packet.

Information about a route should not be sent back in the direction from which the original update came.

The duration in milliseconds (ms) it takes for a network request to go from a starting point to a destination and back again to the starting point.

Important metric in determining the health of a connection on a local network or the larger Internet

The amount of time it takes for a single bit to propagate from the source destination.

Routers

Switches (or Network Bridges)

C) 10000000-10111111 --> 128-191

C) 172.32.0.0

• prefix: network

• suffix: all 0s's

• type of address: network

• purpose: Identifies a network

1. Physical Layer

2. Data Link Layer

3. Network Layer

4. Transport Layer

5. Session Layer

6. Presentation Layer

7. Application Layer

Bit

Data link layer (layer 2)

Physical (Layer 1)

Network and Session

Transport layer

Hub

Switch

Switch

Switch

Hub

Switch

A communication channel that connects two or more devices. The link may be physical or logical that uses one or more physical links or shares a physical link with other telecommunications links. For example, coaxial cable or optical fiber.

Links connecting only 2 nodes. (AKA store-and-forward)

Links allowing more than two nodes to share a single physical medium. (AKA broadcast or shared)

Circuit-switched and packet-switched networks

Point-to-Point

By setting up a total path of connected links from the origin to the destination host and sending a control message that sets up a path from the origin to the destination. (A return signal informs the origin that data transmission may proceed.)

• All channels in the path are used simultaneously

• the entire path remains allocated to the transmission (whether or not it is in use).

Point to Point and Multiple Access

By decomposing messages into small pieces called packets.

These packets are each numbered and make their way through the net in a store-and-forward fashion.

when they are currently transmitting packets

A network packet is a formatted unit of data carried by a packet-switched network.

control information and user data

It provides data (instructions) on how to deliver the payload

For example: source and destination network addresses, error detection codes, and sequencing information.

The headers and trailers

One

They will interfere with each other (interference phenomena)

Each signal being sent should...

1. Have a different frequency from the others

2. Ensure it does not travel at the same time as the others

3. Ensure it does not travel through same medium as the others

the specific use of available bandwidth to achieve specific goals

Multiplexing and compression

The set of all techniques that allow simultaneous transmission of multiple signals across a single data link.

As data and telecommunications use increases, so does traffic

The Data rate of medium exceeds data rate of digital signal to be transmitted

Multiple digital signals are interleaved in time (May be at bit level of blocks)

• preassigned to sources and fixed

• allocated even if no data

• do not have to be evenly distributed amongst sources

• Useful bandwidth of medium exceeds required bandwidth of channel

• Each signal is modulated to a different carrier frequency

• Carrier frequencies separated so signals do not overlap (guard bands) e.g. broadcast radio

• Channel allocated even if no data

• It cannot utilize the full capacity of the system

• Requires ensuring that the adjacent bands do not overlap each other, otherwise the signal in one band may interfere the signal in other band

• Although system has the capacity still in some cases the channel cannot pass the actual signal

the measure of the capacity of a transmission system. It is the range (or band) of frequencies used on the transmission medium. Bandwidth is typically measured in Hertz.

the maximum number of bits that can be transmitted in a certain amount of time over a particular medium.

The measured number of bits that can be transmitted over a particular medium in a given amount of time. Usually, described in bits/sec (or bps).

Bandwidth >= Effective Throughput

the amount of time is takes for a single bit to propagate from one end of a network to another.

AKA delay/end to end delay

The time it takes for a bit to travel from sender to receiver and back again.

1. Propagation delay

2. Transmission Time

3. Queuing & Processing Delays

Calculated using the speed-of-light propagation delay:

• in a vacuum, 3.0 * 10^8 meters/sec

• in a cable, 2.3 *10^8 meters/sec

• in fiber, 2.0 * 10^8 meters/sec

the amount of time it takes to transmit the data onto the transmission media.

This value is a function of the bandwidth and the packet size.

This is the time the data spends in being processed and waiting for its turn (Queuing) to be transmitted.

This value is almost impossible to calculate.

Tp (Propagation Delay) = (Distance across link)/(Speed-of-light delay)

Tx (Transmit Time) = (Size of data )/(Throughput)

Tq (Queuing & Processing Delay) = This is hard to measure so a statistically generated value or a constant is used. (depends on congestion)

• Distance = length of the wire over which the data will travel (usually meters/sec)

• Speed-of-light = effective speed of light over the channel

• Size = size of the packet (usually bits)

• Throughput = #bits/(unit time) at which the packet is transmitted (usually bits/sec)

Capacity = (Delay) * (Bandwidth)

sends a message to the specified computer and waits for a response. ping reports its findings.