CIS 3500 Networking Midterm

Denial of Service (DoS)

An overload of illegitimate requests from one source to where a server can’t handle it

Distributed Denial of Service (DDoS)

An overload of illegitimate requests from multiple sources to where a server can’t handle it

ISPs (Internet Service Providers)

Help hosts connect to networks

Host

Any device that’s connected to the internet

Internet of Things (IoT)

Connecting everyday physical objects to the internet (smart lightbulbs, smart thermostats)

Internet Engineering Task Force (IETF)

Sets standards for the internet

Server farms

Have hundreds or thousands of equipment racks that hold several servers on each shelf

Server hosts

Provide services to client hosts

Client Process / Application (Browser)

Sends an HTTP request message to a webserver

Webserver Process / Application

Sends an HTTP response message to a client host

Network Application Software

Creates a short application message and translates the message for the receiver

Transport Process

Determines if there’s a confirmation and adds a TCP header to create a TCP segment

Internet Process

Decides how to send the message and puts the TCP segment into an IP packet

Hardware and Operating System’s role in the Network Stack

Sends the IP packet to the internet

IP packet

Contains an application message (or fragment)

Transport process (end-to-end)

Host-to-host process where the transport process on the client PC talks to the transport process on the server

DHCP server

Assigns IP addresses to clients

DNS (Domain Name System)

Like a table that converts human-friendly website names to numeric IP addresses that computers can read

Network Standards (Protocols)

Rules of operation that specify how two hardware or software processes work together by exchanging messages

ISO and ITU-T

Create a variety of network standards

Physical layer standards

Govern transmission between adjacent devices connected by a transmission medium

Data link layer standards

Govern the transmission of frames across a single switched

Internet layer standards

Govern the transmission of packets across the Internet as a whole

Transport layer standards

Govern aspects of end-to-end communication between two end hosts not handled by the Internet layer

Application layer standards

Govern how two applications work with each other

Data field (message syntax)

The information carried by a message

Header (message syntax)

Everything before the data field (such as source and destination address fields)

Trailer (message syntax)

Everything that comes after the data field

Packet

A long string of bits where the first bit is bit 0 and fields are consecutive groups of bits

IPv4 Version Number (VN) field

Specifies version 4 (IPv4) or version 6 (IPv6)

IPv4 Header Checksum Field

Used by the receiver to check for errors in the header; if recalculated values don't match

IPv4 Address Fields

Source and Destination IP addresses

TCP Sequence numbers

Allow receivers to put segments back in order if they arrive out of order

TCP Acknowledgement numbers

Allow the receiver to tell which segment is being acknowledged

TCP Flag fields (9)

Fields where if flag=1 it is set and if flag=0 it is not set

TCP Checksum

Used to check errors between the TCP header and data field with attempts to fix problems (reliable)

UDP Length

Length of the UDP data field in bytes

UDP Checksum

Used to check for errors in the entire datagram; discarded if an error is found with no retransmission (unreliable)

Server Port Numbers

Numbers (0–4999) assigned by multitasking servers to distinguish different applications (0–1023 are well-known

Socket

An IP address

Fields

The header and trailer divided into parts such as source and destination address fields

Quality of service (QoS) metrics

• Speed (measured in bits per second)

• Errors (percentage of incorrect bits, packets)

• Availability (Percentage of time network is available to users)

• Latency (Time delay in packet delivery, measured in ms)

Rated speed

The speed stated in the standard or quoted by your provider

Throughput

The speed you actually get

Jitter

The variability of latency over time (low jitter means low changes

Service Level Agreements (SLAs)

Guarantees for performance with penalties if metrics aren't met

Leased lines

Always-on connections between two geographically separated sites

Redundant lines

Backup lines created so traffic can reroute if a direct line fails

Methods to deal with traffic peaks

Add extra capacity

Traffic shaping

Tries to prevent occasional traffic peaks by reducing traffic allowed into the network

Ping message

Sent to an IP address to test reachability

Local Area Networks (LANs)

Operate on customer premises owned by the organization using the network

802.11 Working Group

Creates WiFi standards

802.1 Working Group

Creates security standards

Trunk links

Connect switches to other switches

Port number

A numerical identifier in networking used to distinguish different applications running on a single device.

TCP

A transmission protocol that provides reliable communication between devices over a network, ensuring data is transmitted in order and without errors.

UDP

A transmission protocol that allows data to be sent without establishing a connection, prioritizing speed over reliability.

Overprovisioning

A networking technique that involves allocating more resources, such as bandwidth or storage, than are actually needed to ensure that performance meets demand, particularly during peak usage.

Priority

A networking technique that allows certain types of data traffic to be transmitted faster than others, ensuring efficient performance during high-demand periods.

QoS

A networking technique that gives Quality of Service to some traffic (like reserved seats). The Quality of Service traffic will always go through but all other traffic is worsened.

Multimode optical fiber cable

Data transmission medium where light reflects rod pure glass at an angle (like a mirror). Has a hollow rod of glass in the core which directs light.

Single mode optical fiber cable

Data transmission cable Laser light that has no modal dispersion and can be used for very long distances

Digital transmission

In digital transmission, there are a few states (2, 4, 8, 16…) more than one bit is sent in each clock cycle

Binary transmission

In binary transmission, there are two states (1 or 0) Once bit is sent in each clock cycle

4-pair UTP

Copper wires organized as four pairs whose two wires are twisted around each other

Optical fiber

Carries signal pulses through glass

Link aggregation

When you use two or more links (optical fiber cords) in between switches. This increases the speed that data can be transmitted

Ethernet Switch

Aa networking hardware device that connects multiple wired devices—such as computers, printers, and servers—together on a Local Area Network (LAN) and manages data traffic between them

MAC Address Tracking

When an Ethernet switch reads the MAC address (Media Access Control address, a unique physical identifier hardcoded into every network device) inside incoming data frames.

CAM/LUT tables

CAM/LUT Tables: The switch builds and maintains a Content Addressable Memory (CAM) or lookup table that maps specific device MAC addresses to its physical ports.

Hexadecimal notaion

• 0-9 (base 10) = 0-9 (hex)

• 10 = A

• 11 = B

• 12 = C

• 13 = D

• 14 = E

• 15 = E

Backup link

When a link fails between to switches there are ______ put in place

They are only activated when necessary to prevent infinite loops of data transfer from switch to switch (see below)

VLANs (Virtual Lans)

Virtual Lans segregate traffic, can are broken but is quite secure

802.1X authentication

Supplicant must be verified by an authentication server before being allowed to use the switch its attached to