CS250 - Unit 3 (Networking & Internet Architecture)

All communications in networked systems are based on sending and receiving messages

- No shared memory - Sending message from A to B 1) build message in A 2) Send message over network 3) reconstruct message at B

As Bandwidth increases...

- Speed of light does not change - High-speed does not mean that latency improves at the same rate as bandwidth

Manchester encoding

0 is a low-to-high transition. 1 is a high-to-low transition; doubles the rate at which signal transitions are made on the link

well-known ports are in a range from ?

0 to 1023

A frame includes:

1. A header describing the frame 2. A payload of data 3. A frame footer used to detect errors

Things that could go wrong with packets

1. Lost 2. Corrupted 3. Misdelivered 4. Out of order and duplicates

Subnetting divides the IP address into two parts:

1. Network prefix 2. Host Identifier

Store-and-forward

1. Receive complete packet over link 2. Store packet in internal memory 3. Forward complete packet to another node (Used by Packet Switched Network)

What are the differences from IPv4 and IPv6

1. Source and destination addresses are bigger in IPv6 (16 bytes) 2. IPv6 does not have options in the frame header 3. IPv6 does not have fragmentation (now endpoints are responsible) 4. IPv6 has no checksum

What are the three components of latency?

1. Speed-of-light propagation delay 2. Amount of time to transmit a unit of data 3. Queueing delays

The four layers of the protocol suite are

1. The link layer 2. The internet layer 3. The transport layer 4. The application layer

If all fragments do not arrive at receiving host?

1. receiver gives up reassembly 2. discards fragments that didn't arrive

The IP Packet header is represented as a succession of __ bit words.

32

Fragmentation occurs at ___byte boundaries

8

Non-Return to Zero (NRZ)

A binary signaling technique that increases the voltage to represent a 1 bit but provides no voltage for a 0 bit.

Router

A device that connects subnets and operates at the internet layer

Multiplexing

A form of transmission that allows multiple signals to travel simultaneously over one medium.

Baseline Wander

A problem with NRZ because of consecutive 1's and 0's

Clock Recovery

A problem with NRZ where sender and receivers clocks must be perfectly synchronized

IP Packet: SourceAddr

Address for where the datagram is coming from; used to decide if packet should be accepted

IP Packet: TOS (type of service)

Allow packets to be treated differently; Based on application needs

Internetwork

Arbitrary collection of interconnected networks

Addresses and subnets

Computers connected to the same local network are said to be on the same subnet. They also have IP addresses that begin with the same leading bits

Full-duplex

Data can flow in both directions at the same time

Half-duplex

Data can only flow one direction

The IP service model

Datagram model of delivery - connectionless; best effort Addressing scheme - identifies all hosts in the internetwork

IP Packet: DestinationAddr

Full address of destination; forwarding decisions are made at each router

fragments carry the same identifier in the _____ field

Ident

Destination network port number

Identifies the specific service or process that will receive the data

Keeping routers simple was one of the original design goals of IP

Important to run over everything

Switched networks

Indirect connectivity among cooperating nodes

Client Socket

Initiates connections; When a client socket on a remote host attempts to connect to that server port: 1 - Server wakes up 2 - Negotiates a connection between client and server 3 - Opens a regular Socket between two hosts

Maximum Transmission Unit (MTU)

Largest IP datagram that can be carried in a type of network connection - every network type has a maximum transmission unit

IP Packet: Length

Length of the datagram in bytes

IP Packet: Version

Makes it easy to redefine packet format later

Bandwidth

Number of bits that can be transmitted over a network at a given time; also called throughput

Modulation

Objective is to send a pair of distinguishable signals, varying frequency, amplitude, or phase of the signal to transmit info

IP Packet: Options

Optional field in the IP packet header; without options the header is 20 bytes

Encapsulation

RRP receives a set of bytes to transmit; RRP is responsible for sending this data to its peer at the other end - low level protocol does not interpret message given to it by the high level protocol. - low level protocol may apply simple transformation to the data it is given

Layering

Services at higher layers implemented in terms of lwoer layers Advantages - Breaks problem up into manageable components; provides modular design; Each layer can be changed independently of the other

IP Packet: HLen

Specifies length of header in 32-bit words

The two foundational protocols in the internet protocol suite are ____.

TCP and IP

The internet protocol suite is designed around a four-layer model, sometimes called the ___?

TCP/IP model - The IP suite standardizes the method of communication on the internet

Baud Rate

The rate at which signals on a wire may change.

Latency

Time it takes for a bit to travel from its sender to its receiver.

Server Socket

Waits for connections; Listens for incoming network connections on a particular port on the host that it runs on

Address

a byte string connected to a node to distinguish between other nodes in a network.

The socket abstraction

a door that allows programs on a computer to communicate with other programs across a network. It acts as an endpoint for sending and receiving data between devices. Think of it as a combination of an IP address (like a street address) and a port number (like an apartment number). The IP address locates the device, while the port number identifies a specific service or application running on that device. Sockets enable programs to establish connections, send and receive data, and communicate with each other over a network, regardless of whether it's a local network or the internet. They provide a way for applications to interact and exchange information across different devices in a networked environment.

Packet Switched Network

a type of network in which nodes send discrete data blocks to each other (packets)

Circuit Switched Network

a type of network in which the nodes communicate by establishing a dedicated circuit across a set of links

Protocols

abstract objects that comprise layers of a network system

Networking layers represent an ___?

abstraction

Protocols at the application layer focus on

accomplishing a specific task

MAC address

address on the link layer that uniquely identifies it

IP address

address used at the internet layer to uniquely identify a host on the global internet

The transport layer relies on the internet layer for ____ and ____.

addressing, routing

More accurate to think of network as allowing ____ to communicate

applications - identify and build right set of common services

What is the term for data that is being transmitted?

body or payload

IP Packet: Checksum

checks for corruption

A computer network is a system that allows computing devices to _____with each other

communicate

Data sent with UDP is known as a ?

datagram

The transport layer has a ____ for the address

destination network port number

Link layer protocols are used by ________ to communicate with each other

devices on the same network

Application data is said to be ___?

encapsulated

Router/Gateway

forwards messages between networks

Link layer data is divided into small units known as ___

frames

dynamic ports

have a value greater than 49,151

IP is the key tool to build scalable, _______ networks

heterogeneous

IP Packet: Protocol

holds the demultiplexing key

IP Packet: TTL (time to live)

how long the data can live

What does the Delay x Bandwidth product tell us?

how many bits fit in the pipe; how many bits in flight

IP Packet: {Indent, Flags, Offset}

information about fragmentation

What is the demux key?

information included in the transport layer header to identify the application

If the Next Header field is non-zero in IPv6?

it defines an extension header (basically options)

Protocols at the internet layer rely on ______ layer protocols to communicate on a local network

link

MAC addresses are only usable on a _______.

local network

A host with a single IP address can have _____ active ports

multiple

A ____ must provide connectivity among a set of computers

network

The Internet is a ________.

network of networks - a globally connected set of computer networks that all use a suite of common protocols

Network protocols operate in a layered model, with the implementation being called a ?

network stack A protocol at a certain layer doesn't have to concern itself with the entire networking stack; only the layers with which it interfaces

When things go wrong with a packet, the network does ____

nothing

Data sent over the internet layer is called a ______, which is enclosed in a link layer frame

packet

Datagram is a type of ?

packet sent in a connectionless fashion - no need for advance setup

registered ports are

ports that can be registered with the (IANA). range from 1,024 to 49,151

Transport Layer

provide a communications channel for applications to send and receive data between hosts (TCP & UDP)

Internet Layer

provide a mechanism for communicating across networks. Responsible for identifying hosts with addresses and enabling the routing of data from network to network across the internet.

Link Layer

provide a way to communicate on a local network

Application Layer

provide application-specific functionality - protocols that describe the behavior of application - the lower layers of the stack are the plumbing that enables applications to do stuff

TCP provides a _____ connection between two hosts

reliable

Each network layer represents a _______?

scope of responsibilities

Data sent with TCP is known as a ?

segment

Fragmentation is necessary when datagram path includes network with ______MTU

smaller

The internet protocol suite _____ the method of communication on the internet.

standardizes

Ephemeral ports

temporary ports that the client uses just long enough to complete communication with a server

An application hands off data to a _____ layer protocol for delivery to a remote host.

transport

Not every device is interested in using all 4 layers

true

Statistical Multiplexing

type of multiplexing where data is transmitted from each flow on demand

UDP is a "best effort" protocol, which means its delivery is ?

unreliable

How is data sent?

whatever the physical medium, we use signals

Routing

where switches and routers use a node address to forward the message towards the destination node