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ERIC BRUHN

Network Applications and Network Applications Lab

Chapter One Notes

 

Other Chapter Notes:

[Chapter One]

[Chapter Two]

[Chapter Three]

[Chapter Four]

[Chapter Five]

[Chapter Six]

[NID Outline]

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IP Concepts

Class

Network Bits

Host Bits

Number of Hosts

A

8

24

16 million+

B

16

16

65,000+

C

24

8

255

        •  
        • Classes A, B, and C are unicast, when you send a packet; presumably you are addressing a single machine.
        • Class D is multicast
        • Class E is reserved for experimental use.
        • Address Classes and IP Ranges

Class

Beginning IP

Ending IP

A

0.0.0.0

127.255.255.255

B

128.0.0.0

191.255.255.255

C

192.0.0.0

223.255.255.255

D

224.0.0.0

239.255.255.255

E

240.0.0.0

247.255.255.255

    • Subnet Masks
      • The masks informs a computer how many bits in its IP address have been relegated to the network and how many to the host.
    • Service Ports
      • TCP and UDP have 16-bit port number fields in their respective header fields.
      • This means you can have up to 65,536 different ports.
      • Most processes have an assigned port number, but there is nothing stopping you from changing that number to one of your choosing.
      • Any service can run at any port.
  • IP Protocols
    • Two different transport models
      • Connection-oriented model (TCP)
        • Software ensures that the communication is reliable and complete and begins the process establishing a handshake connection.
        • Ensures that all data sent is received.
        • Reliable because each packet is acknowledged when it is received.  If a packet is not received, it is resent.
      • Connectionless model (UDP)
        • Send and pray delivery.
        • No handshake and no promise of delivery.
        • Just assemble packets and fire them into the network.
        • Application must ignore the missing pieces or ask for them.
        •  
      • TCP is slower than UDP because of all the checking, but because of that it is a lot more reliable than UDP.
    • ICMP (Internet Control Message Protocol)
      • Ping
      • Determine if a given network host is reachable.
      • More information in Chapter 4.  
    • IP Header Table
  • Domain Name System
    • A.k.a DNS
    • DNS is a distributed database because the entire address table is not stored on a single host.
    • Distributed across many servers.
    • Translates a domain name to an IP address so you can go to that server.
  • Routing: How you get there from here
    • TCP/IP network layer is concerned with routing and how to get from one host to another.
    • Layer where IP addresses are used.
    • ARP is used to get an IP address from a MAC address so a packet can be sent.
    • When the destination host is not on the local network, the traffic is sent to a default router.
    • That router is responsible for sending the packet one hop closer to its destination.
    • Routers maintain tables of routes that they know about. They use dynamic routing protocols to update their tables.
    • Routing Protocols:
      • Interior Gateway Protocols (IGPs)
        • Routing traffic within a network that is under the same administration, also known as Autonomous System (AS).
        • Routing Information Protocol (RIP)
        • Open Shortest Path First (OSPF)
      • Exterior Gateway Protocols (EGPs)
        • Required when packets must travel between different Autonomous Systems.
        • Border Gateway Protocol (BGP)is a widely used EGP.
        • Currently provides routing protocol that supports the internet backbone.
        • BGP servers must maintain routing table that include all of the external addresses on the internet.  
  • TCP Header Table
  • Ethernet Frame Header

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