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TCP/IP Design goals:
- Hardware, software independence
- Built-in failure recovery
- Reliable service even with high error rates
- Efficiency; low data overhead
- Allow adding new networks without service disruption
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Benefits of TCP/IP
- Open standard; hardware/software- independent
- Operating system-independent
- Separated from underlying hardware
- A routable protocol
- Includes reliable, efficient data-delivery mechanisms
- Uses common addressing scheme
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Describe IP
- Internet Protocol operates at the Network layer of the OSI model
- Routes data to destination
- Connectionless (best effort transmission)
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IP header includes:
- Source and destination address
- Protocol number
- Checksum
- Code representing the enclosed higher-layer protocol
- TTL (Time to Live) field: Contains hop count
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Describe TCP
- Ensures reliable, verifiable data exchange
- Provides connection-oriented transmission
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TCP header Includes:
- Source and destination port numbers
- Datagram sequence number
- Control bit flag indicating how the segment should be handled
- Checksum
- Window
- Urgent Pointer
- Enables fragmented datagrams and their reassembly.
- -Sequence number
- -Fragmentation offset value
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Key features of TCP communication
- Flow control(flows at slower speed of 2 devices)
- Acknowledgment(ACK, NAK)
- Sequencing(put packets in proper order)
- Checksums(error control)
- Retransmission of lost segment
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Describe an IPv4 address
- 32-bit number represented as a four-part decimal number.
- Often called dotted-decimal notation
- Each byte (octet) can have decimal value of 0 – 255
- Two portions: Network identifier+Host identifier
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What the default subnet masks for class A, B, C?
- A 255.0.0.0
- B 255.255.0.0
- C 255.255.255.0
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How are the two portions of an IPv4 address identified?
- Network portion then host portion
- all 1's for network portion followed by all 0's for host portion
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ICANN
- Internet Corporation for Assigned Names and Numbers (ICANN)
- Registers, maintains IP addresses
- Registered IP addresses only required for connecting to Internet
- not private IP addresses
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How are private ip address different from none-private?
- Not recognized by Internet routers
- Require Network Address Translation (NAT), proxy servers to replace them with valid Internet address
- Used inside corporate networks (reduces demand for IPv4 Addresses)
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What is NAT?
- Network Address Translation
- Is the process where transmissions can be routed appropriately from an outside system to internal systems with private IP addresses
- Makes it possible to hide the internal IP addresses from external systems
- Is built into most routers and firewalls
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Internet Proxy Servers:
- Act as intermediaries between systems
- Check and validate incoming requests to see if it can fulfill the request before passing it on to the server
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Class A:
- Designed for very large networks only
- 0,7bits network, 24bits host
- 10.0.0.0–10.255.255.255 (10.0.0.0 /8)
- First octet value of 126 or less
- A first octet value of exactly 127 indicates a software loopback test address
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Class B:
- Designed for medium-sized networks
- 10+14bits network + 16bits host
- 172.16.0.0–172.31.255.255 (172.16 .0.0/16)
- First octet value of 128 through 191
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Class C:
- Designed for smaller networks
- 110+21bits network + 8bits host
- 192.168.0.0–192.168.255.255 (192.168.0.0 /24)
- First octet value of 192 through 223
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Class D:
- Multicast address range; cannot be used for networks
- 1110+28bits
- First octet value of 224 through 239
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Class E:
- Reserved for experimental purposes
- 1111+28bits
- First octet value greater than 239
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IP subnet:
- Uses host address bits as additional network bits, creating additional networks.
- Can be routed independently, allowing a much better use of address space and bandwidth
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Subnetting Advantages:
- Minimizes network traffic
- Isolates networks from one another
- Improves performance
- Defines limits of a broadcast domain
- Optimizes use of IP address space
- Enhances the ability to secure a network
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What are the address portions for specific computer with ip 142.155.40.10 and subnet mask 255.255.255.0?
- 142 is class B so default subnet is 255.255.0.0
- network is 142.155
- subnet is 40
- host is 100
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CIDR
- Classless Interdomain Routing (CIDR)
- CIDR is an alternative to representing addresses as an IP address or subnet mask
- Described as “slash x (/x)” networks
- X represents number of bits in the IP address range used as the network address
- With CIDR, Class C network becomes a /24
- Reduces routing table size
- Used to define networks that fall between old classifications
- /21 subnet mask: 255.255.248.0
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Private Addresses Benefits:
- Network set up without registering addresses
- Boundary between network and Internet
- Prevents hosts on the Internet from knowing the internal addressing scheme of the network
- (Used for setting up network with public addresses used as connections to Internet)
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port number (port address):
- applications associated with data
- source port for the source application
- destination port for the destination application
- Range 0 – 65535
- Windows: \windows\system32\drivers\etc
- Two types of ports: UDP ports, TCP ports
- Each port is assigned a unique 16-bit number
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socket
- A socket is a combination of IP address, associated protocol, and port number
- Identifies a single network process
- Two sockets required for connection-oriented protocols
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IPv6 uses:
- 128-bit addressing scheme
- 8 sets of 4 hexadecimal digits
- 3FFE:0B00:0800:0002:0000:0000:0000:000C
- May be abbreviated (drop leading 0s, single groupings of 0s)
- 3FFE:0B00:0800:0002::000C
- Each host has three addresses:
- -Host ID, Network ID, Routing information
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FQDN
Fully Qualified Domain Name (FQDN) consists of a host name and a domain name
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Name resolution:
- Finding IP address of domain name.
- Resolution methods include:
- HOSTS file
- Domain Name System (DNS)
- Windows Internet Naming Service (WINS)
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Top-level domains:
- .com: commercial organization
- .edu: educational establishment
- .gov: branch of the U.S. government
- .int: international organization
- .mil: branch of the U.S. military
- .net: network organization
- .org: nonprofit organization
- Plus many more
- ICANN: Assigns Internet domain names
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DNS
- Translates host names, domain names to IP addresses
- Uses zone file (DNS table):
- Updated manually, or automatically in dynamic DNSs
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DHCP
- Dynamic Host Configuration Protocol (DHCP): Centralizes management of IP addresses
- DHCP scopes: pools of IP addresses assigned for leasing to clients
- Four messages:
- DHCPDISCOVER
- DHCPOFFER
- DHCPREQUEST
- DHCPACK (DHCPNACK)
- APIPA (Automatic Private IP Addressing): Can enable host to use when no address received from DHCP server
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Most commonly used utilities
- ping
- pathping
- tracert (traceroute)
- ipconfig (ifconfig)
- nslookup (dig)
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ping:
- Tests communication between two hosts
- Reports host response and round-trip time
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pathping:
Returns information about routers in path
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tracert:
- Route information
- tracert on Windows, MS-DOS
- traceroute on Unix, Linux
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ipconfig, ifconfig
- Report IP configuration information
- Manage automatic IP address configuration
- ipconfig: Windows
- -ipconfig
- -ipconfig /all
- -ipconfig /release
- -ipconfig /renew
- ifconfig: Unix, Linux
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Nslookup, Dig
- Used for troubleshooting DNS servers
- -Returns hostname and IP address of default DNS server.
- -Tests DNS server operations
- -View and set DNS server options
- nslookup: Windows NT and later, Unix, Linux
- dig: Unix, Linux
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