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