Wireless
Wireless Bridges used to connect to wireless segments together
Wireless Network modes
Ad-hoc
Infrastructure
802.11 2Mbps 2.4 GHz
802.11a 54 Mbps 5 GHz
802.11b 11 Mbps 2.4 GHz
802.11g 54 Mbps 2.4 GHz
HomeRF 2Mbps 2.4 GHz
Wireless collision avoidance DCF – Distributed Coordination Function
Physical Topology
Bus –consists of some number of machines connected to the network via the same piece of cable uses coax – backbone Thicknet- have to terminate ends otherwise signal problems, i.e. packet storms
Star- all machines connected to a central wiring point, switch used single point of failure
Ring- computers connected to a ring of cable, uses token to decide how can transmit speeds top at 16 Megs. Takes a lot more programming – cost much higher
Mesh- each machine has a dedicated connection to every other machine on the network, full and partial
Cable
Coaxial cable – shields against electro – magnetic interference, copper wire
RG- 8 Thick Ethernet oldest coax cabling still in use, 50 Ohm rating and yellow or orange/brown color
RG-62 rated at 75 ohms, used with ArcNet
RG-58 Thinnet 50 Ohm rating
Twisted Pair
Shielded Twisted Pair
Twisted pairs of cable protect against EMI
Used in Token Ring and High Speed networking
Unshielded Twisted Pair
No protection from EMI
Cheap
Fiber
Transmit light
Single and multimode
Components – The fiber, cladding, which is the part that makes the light reflect down the fiber and Insulating jacket
Can reach 10,000 meters
OSI MODEL- People Don’t Need To See Paula Abdul
Application layer- interacts with the user
Protocols
HTTP - WebPages
FTP - Files reliable delivery
DNS - domain name to I.P address
TFTP - “Trivial” no guarantee of delivery, connectionless and faster than FTP less over head
Raw user data
Presentation Layer- user data presentation (presents user with data), compression/decompression, encryption and decryption
Protocols
.DOC, .JPG, .GIF and .MP3
Raw data
Session Layer – manages connections between machines on the network
Sets, maintains, tears down sessions
Dialogue Control
Simplex communication - one way com
Half duplex - either way but only one at a time
Full duplex – full two way communication
Raw data
Transport Layer - getting the information there
Protocols
*TCP – transmission control protocol = work horse
Chops up file into segments, numbers segments and has port number guarantees delivery
UDP – user data protocol, doesn’t guarantee delivery
Network Layer –
Protocols
IP –encapsulates segments into packets, adds IP address (32 bits for address) responsible for delivery
Responsible for global addressing and routing
ICMP – error control, PING –verifies the address is good and alive
Data Link Layer – defines the rules for accessing and using the Physical layer
Protocol
Ethernet
Frames – puts information around packets – MAC address – your network card address, used on the LAN to identify machine
ARP translates MAC to IP address, identifies which packet belongs to which Network – machine answers with MAC to receive packet
Sub Layer
Logical Link Control 802.2 provides an interface with the Network Layer Protocols
Mac Access Control controls access to physical layer
Physical Layer - defines the physical form of the data across the cable
Electro mechanical, data in Bits
RF-45
RF- 11
CAT 5, UTP
Just playing with Wordpress 2.5
Rumor: Constructicons Coming in Transformers 2?! « FirstShowing.net
Ah fuck yes!! They just need to add some Dinobots as well to what’s looking like the perfect movie.
“Grimlock Smash!!
Worlds biggest inventions fair features self-making bed - USATODAY.com
Hell yes about time. I hate, I mean hate making the bed. The concept of this bed is one I can get behind. I am not sure why but I have never been a big one to make my bed. Maybe cause making the bed was never forced on me as child or perhaps just simply laziness. If I get the chance to pick out the next bed I sleep in its going be this one or the cheaper big box store version that will hopefully come out someday.
simply awesome
It’s Awesome, check the rest of the series here
Real-life Transformers: Shape-changing robots could help save lives | the Daily Mail
Man this sounds so familiar to me…Oh yeah I know where
Shit where’s a time dilation device when you need one!!