How Bits and Bytes Work 1 Bits The
How Bits and Bytes Work 1
Bits ØThe word bit is a shortening of the words "Binary dig. IT ” ØComputers operate binary number system Bytes ØBits are bundled together into 8 bits and form 1 Byte= 8 bits 1 Kilo Byte=1024 bytes 2
Online Presentation http: //www. learntcpip. com/LTSN/binarymath_files/Default. ht m#nopreload=1&TOCEntry=1 3
Units in Data Transmission Bits Per Second ( bps ) – Measure of Data speed in an second 1 Kbps 1 Mbps = = 1, 024 bps 1, 024 Kbps Computer modems for telephone line operates at app 57. 6 Kbps A web page on an average would be 40 to 50 Kilobytes in size 0/1 1 B 1 Kb 1 Mb 1 Gb = = = 1 bit 8 Bit 1, 024 Bits 1, 024 Kilobits 1, 024 Megabits 4
Bit rate The bit rate is the number of bits that pass a given point in a network in a given amount of time, usually a second. Thus, a bit rate is usually measured in some multiple of bits per second - for example, kilobits, or thousands of bits per second (64 Kbps or 128 Kbps ). 5
Speed always measured in bits…. . ØThis computer has a 32 -bit Pentium processor ØThe computer has 128 Mb RAM ØThis modem works up to 56 Kbps. . ØThe connection speed for DSL is 128 kbps. . 6
Internet Protocol • Provides communication between hosts of different kind of networks • This includes the information about the network of destination • Every Host/Computer has a unique IP address • IP addresses are logical addresses (not physical) • Size of IP address is 32 bits. 7
IP Addresses Class of IP Address Class A : First octet used for Network Addressing Class B: First 2 Octets are used for Network addressing. Class C: First 3 octets used for Network addressing. 8
Class A l 128 possible network IDs l over 4 million host IDs per network ID Class B l 16 K possible network IDs l 64 K host IDs per network ID Class C l over 2 million possible network IDs l about 256 host IDs per network ID 9
IP Addressing If you look at the IP Address, the number are broken into different categories. 216. 27. 61. 137 Classification Hosts 216. 27. 61. 137 Octets 10
IP Addresses • IP Addresses are usually shown in dotted decimal notation: 1. 2. 3. 4 000000010 00000011 00000100 • www. google. com is 128. 213. 1. 1 10000000 11010101 00000001 11
IP ADDRESSING An IP address (IP stands for Internet Protocol) is a unique 32 -bit number that identifies the location of your computer on a network. Basically, it works like your street address -- as a way to find out exactly where you are and deliver information to you. For example, 1. 160. 10. 240 could be an IP address. Four regional Internet registries -- ARIN, RIPE NCC, LACNIC and APNIC -- assign Internet addresses from the following three classes. Class A - supports 16 million hosts on each of 126 networks Class B - supports 65, 000 hosts on each of 16, 000 networks Class C - supports 254 hosts on each of 2 million networks What's the difference between a Public IP Address and a Private IP Address? A Public IP Address is a globally unique number that identifies a device on the Internet. If you want someone on the Internet to connect to you, then you must tell them your public address. Also known as your “real” or “external” address. 12
IP ADDRESSING A Private IP Address are typically assigned to devices on a LAN (Local Area Network) and are not used outside the LAN. These IP addresses are typically used where you have multiple computers all sharing the same Internet connection. There is a range for private IPs in each of the three classes of IP addresses Class A - 10. 0 through 10. 255 Class B - 172. 16. 0. 0 through 172. 31. 255 Class C - 192. 168. 0. 0 through 192. 168. 255 Note: IP’s provided with commercial plans are Static IP’s and for rest of the plans IP’s are Dynamic in nature. 13
LOOPBACK Loopback - The IP address 127. 0. 0. 1 is used as the loopback address. This means that it is used by the host computer to send a message back to itself. This IP address is also used to check the Proper functioning of LAN Card. 14
COMMON TCP/UDP Ports In TCP/IP and UDP networks, a port is an endpoint to a logical connection and the way a client program specifies a specific server program on a computer in a network. Some ports have numbers that are preassigned to them by the IANA, and these are known as well-known ports numbers range from 0 to 65536, but only ports numbers 0 to 1024 are reserved for privileged services and designated as well-known ports. This list of well-known port numbers specifies the port used by the server process as its contact port. 1 TCP Port Service Multiplexer (TCPMUX) 5 Remote Job Entry (RJE) 7 ECHO 18 Message Send Protocol (MSP) 20 FTP – Data 21 FTP – Control 22 SSH Remote Login Protocol 23 Telnet 25 Simple Mail Transfer Protocol (SMTP) 29 MSG ICP 37 Time 15
COMMON TCP/UDP Ports 42 Host Name Server (Nameserv) 43 Who. Is 49 Login Host Protocol (Login) 53 Domain Name System (DNS) 69 Trivial File Transfer Protocol (TFTP) 70 Gopher Services 79 Finger 80 HTTP 103 X. 400 Standard 108 SNA Gateway Access Server 109 POP 2 110 POP 3 115 Simple File Transfer Protocol (SFTP) 118 SQL Services 119 Newsgroup (NNTP) 16
COMMON TCP/UDP Ports 137 Net. BIOS Name Service 139 Net. BIOS Datagram Service 143 Interim Mail Access Protocol (IMAP) 150 Net. BIOS Session Service 156 SQL Server 161 SNMP 17
Port level Security Port level security is implemented through a host based firewall (Zone Alarm) The same security can also be implemented by disabling few services. Click start> settings>control panel>Administrative tools>Services Disable services like TELNET, REMOTE REGISTRY, MESSENGER. Virus attacks come in these ports. 18
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