chptr13 Flashcards
NIC Network Interface Controller
serves as the hardware interface between computer and network
End to end channel
nic to cloud/sps to nic
Open Systems Interconnection Reference Model OSI
theoretical model as a standard by ISO - used for research
TCP/IP
integrated suite consisting of numerous protocols that control aspects of data communication - 5 layers: Application - Transport - Network - Data Link - Physical
Protocol Stack
each layer of the stack at the sending node contributes information that will be used by the corresponding peer layer
Program Applications
Safari - Outlook - Skype etc
Network Applications
designed to present the message to the network in a format that can be understood by each of the hardware and software components of the channel - standard protocols part of TCP/IP
Application Layer
contains the program and network applications
Ethernet
comprises layers 1 and 2 of the tcp/ip protocol suite - Physical and data link layers
frame
bits of an Ethernet packet sent through a single link from one node to another in a LAN
non-Ethernet packets
also called frames at the data link layer
not a node
hub switch or Wi-Fi access point are transparent to data being moved
Physical Layer
Level 1 - layer at which the communication actually takes place. Includes medium - signaling method - specific signal parameters - voltages - carrier frequencies - lengths of pulses etc. Sync and timing issues
Data Link layer
Level 2 - responsible for transmission and delivery of packets across the communication link between nodes. Two sublayers Medium Access Control MAC and
Logical Link Control LLC
collision
two messages collide
Carrier Sense Multiple Access with Collision Detection CSMA/CD protocol
Ethernet - connections are point to point and collisions are not possible.
MAC Address
Address for each node on the Ethernet network - permanently assigned by the IEEE org to manufacturers of Ethernet attached equipment. NIC
Network Propagation delay
the amount of time it takes for a packet to get from one end of the network to the other
WI Fi ad hoc mode
assumes direct connections between Wi-Fi nodes and is based on a partial mesh network topology. Depends on a network of available coop stations rarely is used
Wi Fi infrastructure mode
variation of CSMA/CD is used for infrastructure Wi-Fi. Collision handling is required. Delays due to collisions are much longer than those on a wired hub
Carrier Sense Multiple Access with Collision Avoidance CSMA/CA protocol
a station listens until channel clear to transmit. Then transmits frame to access point. When frame reaches its destination the receiver checks for errors then sends a short acknowledgment packet to indicate receipt
Logical Link Control (within Datalink)
resize frame if necessary optional error checking - frame numbering or reordering/recombining frames
Media Access Control (within Datalink)
add frame header. Encode bytes of frames to bits in format and signal type appropriate for medium and signal method of physical layer. On receiving message it decodes bit stream to bytes of frame and removes frame header.
The Network Layer
Layer 3 - responsible for addressing and routing of packets from the source end node through intermediate nodes - step by step - to their proper final destination.
TCP IP Network layer
aka internetworking layer or IP layer
IP datagrams
IP level packets within a LAN
Layer 3 switches
routing takes place at the network layer - routers and gateways are sometimes called this
fragments
ip datagram fragments are reassembled by IP when the final destination is reached using header info that is stored with each fragment. IPv6 rejects fragments instead
ICMP Internet Control Message Protocol
auxiliary protocol that creates error messages that occur when there is a failure in procedures
Transport Layer
Layer 4 - purpose is to take messages from the network applications and provide services that support reliable end to end communications. Responsible for generating the final address of the destination. Responsible for packetization of the message. implemented with 3 different protocols: TCP; USER Datagram Protocol UDP; and Stream Control Transmission Prot SCTP
Port addresses or numbers
16 bits - first 1024 numbers are “well known ports”. Ie port 80
socket
operating systems provide an interface called a socket for comms between apps and trans layer
TCP - Transmission Control Protocol
connection-oriented service. Before any data packets are sent to receiving node TCP at the sending node establishes a connections with TCP at the receiving node. Sends message. Closes the connection. Reliable delivery service
Logical Connection
operates independently of the actual physical characteristics of the network (TCP connector) - separate from the message route
Segments
TCP packets are called this by some network practitioners - since data content is part of an ordered sequence of bytes
handshaking
the brief initial connections made by TCP with a random 32 bit number to number the packets
UDP User Datagram Protocol
used for some applications instead of TCP. Connectionless service. No comms between sender and receiver prior to sending message. Datagram is sent independently. Faster and simpler but no guarantee on delivery. Streaming video is an example
User datagrams
UDP packets are known as this. Contains the message exactly as delivered from the application. App has to divide message into smaller pieces.
SCTP - Stream Control Transmission Protocol
offers features similar to TCP with improvements to fault tolerance and enables multiple messages in byte streams to be transported simultaneously through same connections. Will allow redirect to other ip address if failure in first address.
DNS - Domain Named System/Server
Translates domain names into ip addresses
IP addresses
standards for location resources on the internet.
ICANN
registers domain names and ip addresses
Static IP Addresses
permanently assigned to computers etc
Dynamic Addresses
assigned on an as needed basis using DHCP
DHCP - Dynamic Host Configuration Protocol
Within the application layer - assigns and reclaims IP addresses from a pool of addresses. DHCP client resides on the computer or device being connected which connects to the DHCP server
DDNS Dynamic Domain Name Service
Can provide a link by updating the local DNS server so that a computer with a dynamic address can be open to public.
IPv6
Created since IPv4 addresses are gone. 128 bits long; 256 trillion trillion trillion different ip addresses. Sequence of 8 4 digit hexadecimal numbers
Colon-hexadecimal notation
IPv6 address written in this: 2fc3:4ab2:4470:0001:FFDC:BB54:c126:7001
DNS Root Server
Top of the root directory - 13 servers all over. Handle 50 billion queries a day
Top-Level Domains
.com; .edu; .org; .net; .de; .cn; .uk
country-code top-level domain servers (ccTLDs)
Country identifiers .de; .cn etc
generic top-level domain name servers (gTLDs)
.com; .edu; .org etc.
Second-level or third-level domain names
Registered through ICANN - ie amazon.com etc.
replication
process used to synchronize the multiple dns servers
resolution
translation process when converting a web address to IP address
local DNS server
not part of the dns hierarchy - could be on host machine - on the LAN or isps site
jitter
defined as the variation in delay from packet to packet
QoS Quality of Service
focuses on 2 params: methods to reserve and prioritize channel capacity to favor packets that require special treatment. Service guarantees from contracted carrier services that specify particular throughput - delay and jitter
Differentiated Service DS field
8 bit field - index into a table that defines various classes of service. Routers can prioritize and route packets based on packet class
Network Security
1-5 categories: Intrusion; Confidentiality; Authentication; Data integrity and nonrepudiation; assuring network availability and access control
NS Intrusion
Keeping systems and network intact and free from intrusion
NS Confidentiality
Keeping content of traveling data private
NS Authentication
Verifying identity of source of data being received. Similar to electronic signatures.
NS Data integrity and nonrepudiation
Protecting data against changes and verifying the source of a message.
NS Assuring network availability and access control
Restricting access to authorized users; keeping network up and running to those users
Packet Sniffing
reading of data in a packet as it passes
Physical Access Restriction
limiting access to network wiring and equipment to personnel.
Logical Access Restriction
Limited with intelligent firewall design that blocks public access where it is not required.
Encryption
provides security beyond other measures.
Symmetric key cryptography
requires that the same key be used for both encryption and decryption
Public key-private key cryptography
two different keys - one public other private are used together in various ways to achieve the different goals.
Network Address Translation NAT
Use of private ip addresses behind a router; router must readdress traffic passing between the internet and local network; difficult with large networks; software that is intelligent
