Chapter 1 SE 148
The internet is known as a 1. and consits of 2.
1. "network of networks" 2. interconnected ISPs
what is a DNS? what does it do?
DNS = Domain Name Server. DNS's map domain names to IP addresses. TCP/IP protocol connects a computer to another computer using IP protocol and IP protocol uses IP addresses in order to connect. once your computer has the IP address from DNS based on the domain name the user entered, it then looks within the internal network to find that IP. if it can't find it in the internal network then it goes to your router (to your default gateway) to look for it within the internet
examples of infrastructure that provides services to applications include
Web, VoIP, email, games, e-commerce, social nets
what is a computer network? how is data exchanged in a network? how are connections between nodes within a network established?
a computer network (or data network) is a digital telecommunications network which allows nodes to share resources. in computer networks, networked computing devices exhange data with each other using a data link. the connections between nodes are established using either cable or wireless media
packet-switching occurs when the hosts break _____ messages into packets
application layer
what is circuit switching? what does it guarantee?
circuit switching is a method of implementing telecommunications network in which two network nodes establish a dedicated communications channel (circuit) through the network before the nodes may communicate. the circuit guarantees full bandwidth of the channel and remains connected for the duration of the communication session. the circuit functions as if the nodes were physically connected as with an electrical circuit
what layer(s) do network switches operate on? what do they support?
data link layer (layer 2) and sometimes the network layer (layer 3) and support any packet protocol
Does DSL have shared or dedicated bandwidth?
dedicated
routers use protocols such as ____ to communicate with each other and configure the best route between any two ____
ICMP (Internet Control Message Protocol); hosts
in TCP/IP, what does IP do?
IP in TCP/IP is the protocol that controls routing of information to different computers, different devices, and different servers on the network. IP deals with IP addresses, subnet masks, default gateway, DNS, etc. IP protocol is what allows 2 computers to figure out where the other one is, so that they can start communication. IP is a routable protocol (you can divide networks into multiple sub networks)
what is a hub?
a hub is a common connection point for devices in a network. nubs are commonly used to connect segments of a LAN. a hub contains multiple ports. when a packet arrives at one port, it is copied to the other port so that all segments of the LAN can see all packets
what is a network host and what kind of information does it know? what is a host also known as?
a network host is a computer or other device connected to a computer network. a host contains info about resources, services, and applications to users or other nodes of the network AKA end systems
What is hybrid fiber coax? Homes that use this share what? Unlike DSL why?
a network of cable, fiber attaches homes to ISP router. the homes share access network to cable headend. DSL has dedicated access to central office, this is shared
what is a packet? what does it consist of?
a packet is a formatted unit of data carried by a packet-switched network. it consists of a header and payload
what is a router?
a router forwards data packets along networks. it is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP network. Routers are located at gateways, the places where two or more networks connect.
two instances at the same layer are visualized as ____
connected by a horizontal connection in that layer
protocols control what? what are examples of protocols?
control sending, receiving of messages. examples include TCP, IP, HTTP, Skype, 802.11
examples of communication links
fiber, copper, radio, satelite
in packet switching, each packet is transmitted from router to router (across links) at ____ capacity
full link capacity
fiber optic cable consists of? how is it's speed and rate of error?
glass fiber carrying light pulses, each pulse a bit. high-speed operation (high-speed point-to-point transmission (i.e. 10's-100's Gbps transmission rate) and has low error rate (repeaters spaced far apart and immune to electromagnetic noise)
in TCP/IP, what does TCP do?
once the computers have found each other via IP protocol so that they can communicate, the next step is to actually communicate via TCP. TCP (transmission control protocol) uses windowing, which is the process by which the client computer sends info to the server computer. in TCP/IP, all of the data that's going to be exchanged is broken down into packets. in TCP, those packets are organized in groups are sent at an increasing rate. if you send the entire data at once, it can be garbage when received by the other end. in TCP, computer 1 sends 1 packet all the way to computer 2. then computer 2 sends an acknowledgement back to computer 1 saying it received it. after sending 1 packet successfully, computer 1 will now send 2 packets over to computer 2. after that is successful, the number of packets sent will keep doubling to increase speed. if there is a disruption in connection, computer 1 will go back to sending 1 packet ant restart the process
unguided media signals?
signals propagate freely, (i.e. radio)
what does guided media signal?
signals propgate in solid media: copper, fiber, coax
what does a twisted pair (TP) consist of?
two insulated copper wires (category 5: 100 Mbps, 1 Gbps Ethernet, category 6: 10 Gbps)
data over DSL phone line goes to _____ and voice over DSL line goes to _____ ____
Internet, telephone net
what is a routable protocol vs non-routable?
in non-routable networks, every single computer is connected to every single other computer. this can cause absolute havoc with bandwidth utilization because all of these computers are trying to talk to each other. with a routable protocol (such as IP), you can divide all of those computers into multiple subnetworks and then you have a boundary (which is your router) and then through that router, your computers can try to connect to other subnetworks if needed. routable protocols allow for you to divide huge networks into smaller subnetworks and then being a routable protocol, you connect all of those subnets using routers
network core is both a
interconnection of routers and network of networks
how does TCP/IP version 4 respond to real time communications?
it can be a real problem for real time communications because the whole windowing process can cause a computer to go back down to sending 1 packet and is not sufficient to carry out "real time" (i.e. lags and out of sync)
what is a node?
either a redistribution point (sending) or a communication endpoint (receiving). a node is a connection point that can receive, create, store or send data along distributed network routes
shared wireless access network connects end system to ____ via ____
end system to router via access point
packet-switching store-and-forward process?
entire packet must arrive at router before it can be transmitted on next link
in packet switching, what is queueing and loss? can packets be dropped?
it's when the arrival rate (in bits) to the link exceeds transmission rate of the link for a period of time. then, packets will queue and wait to be transmitted on the link. packets can be dropped (lost) if memory (buffer) fills up
what is the presentation layer?
layer that the operating system is on. when the user interacts with the application layer, the application layer sends info down to the presentation layer. presentation layer problems include device drivers are messed up or something in the OS isn't allowing the user to go onto the internet (i.e. they don't have the right security protocol)
a network host is a network ____ that is assigned to a network ____
network node that is assigned to a network address
what do packet switches forward and how?
packets (chunks of data) through routers and switches
what port is HTTPS on?
port 443
it's vital that the header composition follows a clear unambiguous specification or format why?
to allow for parsing
what is a physical link lie between?
transmitter & receiver
what are types of LAN distance? wifi? transmission rate?
within building (100ft), 802.1 1 b/g/n, 11, 54, 450 Mbps transmission rate
transmission rate is known as
bandwidth
can a host have more than one network address?
yes, each network interface may be uniquely identified. because protocols are frequently layered, more than one protocol's network address can occur in any particular network interface or node. more than one type of network address may be used in any one network
name all of the network layers in top down order
Application layer, transport layer, network layer, data link layer, physical layer
what is DHCP?
DHCP = dynamic host control protocol. every computer needs to know it's IP address, subnet mask, default gateway, and which DNS servers to talk to. there are two ways you can give this info to the computer. 1.) you can give your computer a static IP address (user sits down and plugs in all info manually.) 2.) instead of static IP, DHCP allows dynamic IP addresses. with dynamic IP addresses, when a computer connects to a network, it will call out to the DHCP server, which will then give it an IP address, give it the default gateway, subnet mask, and DNS servers all automatically. DHCP also keeps a record of all the IP addresses it has assigned to make sure it does not give out the same IP address multiple times
What does HFC stand for? Is it symmetric or asymmetric? What is its upstream and downstream transmission rate?
HFC = hybrid fiber coax asymmetric up to 30Mbps downstream & 2 Mbps upstream
what is the difference between HTTP and HTTPS?
HTTP (hyper-text transfer protocol) in terms of security, is completely fine when browsing the web. however, once you enter sensitive data into form fields on a website, HTTP becomes an issue because that information is translated in clear text and can be read by anyone. HTTPS fixes this issue by incorporated SSL to encrypt data being passed. SSL = Secure Socket Layer and is the S (secure) in HTTPS.
what is ICMP? what uses it and what is it used for?
ICMP = Internet Control Message Protocol. it is a supporting protocol in the internet protocol suite. it is used by network devices, including routers, to send error messages and operational information indicating, for example, that a requested service is not available or that a host or router could not be reached
What is frequency division multiplexing?
It's where different channels transmit in different frequency bands. it's used in a cable network (access network)
What is NAT?
NAT = network address translation. before NAT, it was believed that every single device (computer, printer, etc) would need it's own IP address that was unique to the world. with NAT, it's possible for devices to have the same IP address (usually 192.168.1 - 254) within individual local networks. routers still have unique IP addresses to the world, but once you get inside the router, you can reuse IP addresses.
What are the two main internet standards?
RFC (request for comments) is a formal document from the IETF (Internet Engineering Task Force) that is the result of committee drafting and subsequent review by interested parties
how do different layers connect with each other?
a layer serves the layer above it and the layer below it. for example, a layer that provides error-free communications across a network provides the path needed by applications above it, while it calls the next lower layer to send and receive packets that comprise the contents of that path
what is a network switch?
a network switch can be connected to a router with multiple PC ports to expand a LAN. it is essentially a device that filters and forwards packets between LAN segments AKA switching hub, bridging hub, MAC bridge, is a computer network device that connects devices together on a computer network by using packet switching to receive, process, and forward data to the destination.
what does a computer need to give the DHCP server in order for it to assign a dynamic IP?
a scope or range of IP addresses for it to assign between (i.e. 192.168.1 - 254), subnet mask (i.e. 255.255.255.0 a class C subnet mask), what default gateway you want it to give computers (i.e. 192.168.1.1), what DNS servers. the DHCP sever will then give back all the necessary info to your computer along with a lease time (a lease on how long your computer is allowed to own that IP address). half way through the lease time, your computer will automatically attempt to renew its IP address lease. if your computer can't connect to DHCP at the 50% mark, it will try again in another 50% of remaining time, etc, until it can contact it
what is a subnet mask?
a way to segment a network logically so that different computers and different devices cannot talk to other computers and devices on the same physical network. even though 200 computers may be connected to the same network, you may not want them talking to each other
what is the application layer and which protocols are used in it?
application layer - this is the layer that the user is actually interacting with (i.e. Chrome, Outlook). that the contains the shared protocols and interface methods used by hosts in a communications network. TCP and IP are used in the application layer. the application layer only standardizes communication and depends on the underlying transport layer protocols to establish host-to-host data transfer channels and manage the data exchange in a client-server or peer-to-peer networking model
when data is formatted into packets and packet switching is used, the bandwidth of the communication medium can be what?
better shared among users than with circuit switching.
bandwidth is a measurement of ____ and can be either ____ or ____
bits per second of access network, it can be shared or dedicated
give examples of circuit switched networks and packet switched networks
circuit switched networks includes the early analog telephone network. when a call is made from one telephone to another, switches within the telephone exchanges create a continuous wire circuit between the two telephones for as long as the call lasts
how is circuit switching different than packet switching?
circuit switching guarantees full bandwidth but has a hard limit between how many nodes can be connected in the circuit. packet switching can have many more connected nodes to allow for packets to send/receive, but there is still a limit and too many nodes will cause lost packets. packet switching divides the data to be transmitted into packets transmitted through the network independently. in packet switching, instead of beind dedicated to one communication sesstion at a time, network links are shared by packets from multiple competing communications sessions, resulting in the loss of the quality of service guarantees that are provided by circuit switching
routers use ___ and ____ ____ to determine the best path for forwarding the packets.
headers and forwarding tables
Internet provides programming interface to applications. Hooks allow 1. of app programs to 2.
hooks allow sending and receiving app programs to connect to the internet
at network edge consists of
hosts (clients and servers), servers often in data centers
access networks and physical media are either
wired or wireless communication links
home network consists of?
wireless devices, to/from headend or central office (which is the cable or DSL modem), router, firewall, NAT (network address translation), wired Ethernet (1 Gbps), wireless access point (54Mbps), often all of that is combined in one single box (your router)
what is an example of an IP address?
10.1.10.1 or 192.168.1.1
what does a bit propagate between?
transmitter/receiver pairs
Computer communications links that do not support packets (i.e. _____ ) simply transmit data as a _____
point-to-point telecommunications links, transmit data as a bit stream
What are network protocols and give some examples
network protocols govern all of the communication activity in the internet * computer: TCP connection request * server: TCP connection response * computer: get www.google.com * server: <file>
billions of connected computing devices run __1.__ and are known as __2.__
1. network apps 2. hosts (or end systems)
end-end delay
2L/R (assuming zero propagation delay) and is the time for a packet to hit destination and get confirmation
if L = 7.5 Mbits and R = 1.5 Mbps then what is one-hop delay?
5 Mbps (7.5 / 1.5)
DSL has ___ upstream transmission rate and ___ downstream transmission rate
<2.5 Mbps upstream (usually <1 Mbps) <24 Mbps downstream (usually <10 Mbps)
what is the TCP/IP protocol made up of?
TCP/IP (transmission control protocol and internet protocol) is a suite made up of TCP protocol and IP protocol (with a few more protocols in there). TCP/IP protocol is multiple protocols tied together.
what exactly is the difference between a switch and a hub?
The main difference between these two devices is in the method in which frames are being delivered. In a hub, a frame is passed along or "broadcasted" to every one of its ports. it doesn't matter that the frame is only destined for one port. The hub has no way of distinguishing which port a frame should be sent to. Passing it along to every port ensures that it will reach its intended destination. This places a lot of traffic on the network and can lead to poor network response times. a hub must share its bandwidth with each and every one of its ports. when one PC is broadcasting, it will have access to the maximum available bandwidth. if there are multiple PCs broadcasting, then that bandwidth will be divided among all of those systems, degrading performance. a switch keeps a record of the MAC addresses of all the devices connected to it. with this info, a switch knows which system is sitting on which port. when a frame is received, it knows exactly which port to send it to, without significantly increasing network response times. unlike a hub, a switch will allocate the full 10/100Mbps to each of its ports, regardless of how many PCs are transmitting. users will always have access to the maximum amount of bandwidth. this is why a switch is much better choice than a hub
what is a bit stream and what is it's purpose?
a bit stream is a binary sequence of bits. a byte stream is a sequence of bytes. a byte usually a range of 256 distinct values (octets), so it is also known as an octet stream. it is information that's sent from one entity to another
what are point-to-point (P2P) links in telecommunications and in computer networking? Give an example
in telecommunications, a point-to-point connection refers to a communication connection between two nodes or endpoints. an example of P2P is a telephone call, where one telephone is connected to another, and what's said by one caller can only be heard by the other. This is different than a point-to-multipoint or broadcast connection, where many nodes can receive information transmitted by one node. another example of P2P is two way radio. in computer networking, P2P refers to the wire or other connection that links only two computers or circuits, as opposed to other network topologies like busses or crossbar switches that can connect many communications devices
what are pro's and cons to a longer and shorter DCHP IP address lease?
longer lease times such as a year result in much less network traffic from DHCP renewals, but allow less IP addresses to be assigned altogether. a shorter time such as <7days increases the available IP addresses in the network, but causes more network traffic
what is a packet's payload/body?
the data following the header is called the payload or body. the payload or body is the part of the transmitted data (or packet) that is the actual intended message. The payload does not include the headers or metadata
what is packet switching? what uses packet switching?
packet switching is a method of grouping data transmitted over a digital network into packets which are composed of a header and a payload. network switches uses packet switching to connect connect devices together on a computer network
host takes application message, breaks it into smaller chunks (packets) of length L bits. then transmits those packets into access network at transmission rate R. what is the packet transmission delay or time needed to transmit L-bit packet into link?
packet transmission delay = time needed to transmit L-bit packet into link = L(bits) / R(bits/sec)
What is peer-to-peer (P2P)? What do they do?
peer-to-peer (P2P) computing or networking is a distributed application architecture that partitions tasks or workloads between peers. peers are equally privileged, equipotent participants of the application. Peers make a portion of their resources, such as processing power, disk storage or network bandwidth, directly available to other network participants, without the need for central coordination by servers or stable hosts. peers are both suppliers and consumers of resources, in contrast to the traditional client-server model where the consumption and supply of resources is divded
what port is HTTP on?
port 80
wide-area wireless access is provided by? distance? transmission rate? types?
provided by telco (cellular) operator, 10's km, between 1 and 10 Mbps, 3G, 4G, LTE
what is a default gateway?
the default gateway is the router for the subnet that you are on. first, your computer will try to access a computer or website on the local network first. if it cannot find it, then it will go to the default gateway to find that computer or device. the default gateway is essentially what connects your subnetwork to all of the networks that are out there
how to connect end systems to edge routers?
residential access nets, institutional access networks (school, company), mobile access networks
Internet provides what which is analogous to postal service?
service options
Physical media: radio signals are carried in? name some characteristics about it
signal carried in electromagentic spectrum, no physical "wire", bidrectional, propogation environment effects include reflection, obstruction by objects, interference
What are human protocols and give some examples.
specific messages sent or specific actions taken when messages received, or other events. "what's the time?" "I have a question"
what is static IP and what's a potential problem for it?
static IP is when the user sits down and plugs in info for their computer's TCP/IP protocol to work which includes IP address, subnet mask, default gateway, DNS servers. since the user has to assign every device in their subnetwork, if they assign two IP addresses to the different devices, then some packets will go to one device and some packets will go to the other device which will cause a lot of problems
LANs that use switches to join segments are called ____ ____, or, in the case of Ethernet networks, are called ____ ____ ____
switched LANs or switched Ethernet LANs
what do switches and hubs have in common?
switches and hubs both serve as a central connection for all of your network equipment and handles a data type known as frames. frames carry your data. when a frame is received, it is amplified and then transmitted on to the port of the destination PC.
DSL users use existing ____ _____ to central office _____
telephone line, DSLAM (DSL access multiplexer)
what are examples of a network address?
telephone number (public switched telephone network), IP address, IPX address (local area network or LAN), X.25 or X.21 (circuit switched data network), MAC address (used in ethernet)
name some radio link types
terrestial microwave (up to 45 Mbps channels), LAN (i.e. WiFi) = 54 Mbps, wide-area (i.e. cellular) such as 4G cellular = ~ 10 Mbps, satellite - Kbps to 45 Mbps channel (or multiple smaller channels), 270 msec end-end delay, geosynchronus versus low altitude
what is the purpose of a packet's header and what is it's purpose?
the header is the supplemental data placed at the beginning of a block of data being stored or transmitted. the sole purpose of the header is to facilitate payload delivery by containing addressing and other data that is required for the Internet Protocol (IP) packet to reach its intended destination
what is the network layer?
the network layer is the layer that routers operate on. routers operate at the network level. network layer also includes subnet mask, DNS, etc. your IP address is at the network level. anything you do with TCP/IP protocols with IP addresses happens at the network layer. putting in the wrong IP address and not being able to get to where you want to get to is a network (layer 3) problem. if the router dies, it is a network layer problem
what is the physical layer?
the physical layer is all of the wiring and physical stuff that connects computers together. this includes patch panels, patch cords, the cabling, etc. if a cable connecting a computer gets cut, it would be a layer 1 problem
what is the session layer?
the session layer is the layer that deals with the communication creating a session between two computers. if you are going on to a website, your computer has to create a session with the web server that you're trying to access to get data from. if you run a website and your php config or apache config files are not setup properly, your sessions may not be able to connect. the user can get to your web server and can open up whatever web page is on that server, but when a script runs to look at their bank account info, it may not be working properly
what is the data link layer?
this is the layer that switching occurs. all of the switches like ethernet cables are within this layer. MAC addresses reside here (media access control) as well as ARP. every single networking device in the world has a unique MAC address assigned to it
what is the transport layer
this layer is what decides how much info should be sent in one time (how large a block of info or packet should be sent or how long should the computer wait before it receives acknowledgement that info was sent or received). when you're communicating with a website, this is the layer that decides how much info you will communicate to website and how much info website will communicate back. this layer deals with the transport of data back and forth. windowing occurs here (process where computers send info back & forth)
coaxial cable consists of?
two concentric copper conductors, is bidrectional and is used for broadband which has multiple channels on cable and HFC
