Chapter 2 - TCP/IP and the Internet

1. Telnet: allows remote logins
2. FTP: transfers files
3. SMTP: transfers electronic mail
4. Post Office Protocol (POP): supports forwarding of e-mail
5. Kerberos: security protocol that validates passwords and encryption schemes
6. DNS: determines addresses from machine names (converts Internet machine names to IP addresses)
7. SNMP: sends status message and problem reports about the network
   1. agent - provides information about a device
   2. manager - communicates across a network with agents
8. NFS: enables directories on one machine to be mounted on another [developed by Sun Microsystems]
9. RFC: set of functions that enables remote applications to communicate with a server
10. TFTP (Trivial FTP): simple FTP that lacks security
11. TCP: connection-based services
12. UDP: connectionless services
13. IP: handles transmission of information across networks
14. ICMP: handles status message for IP

1. Originally ARPANET (proposed by Advanced Research Projects Agency) to test the viability of packet-switching networks
2. comprised of four Internet Message Processors (IMPs) [UCLA, UCSB, Stanford, & U. of Utah]
3. network installed by Bolt, Beranek, and Newman (BBN) starting in 1968 [used mainly for remote login and remote file transfer]
4. TCP/IP and gateway architecture first proposed in 1974 by Cerf and Kahn
5. TCP/IP version 4 standardized in 1981 through a series of RFCs

• A common set of applications
• dynamic routing
• connectionless protocols at the networking level
• universal connectivity
• packet-switching

1. 10BaseT
2. 10Base2
3. 10Base5
4. 10BaseF
5. IEEE 802.3
6. CSMA/CD

1. Internet Advisory Board (IAB) - "controls" the Internet
2. Internet Engineering Task Force (IETF) - handles implementation and engineering aspects of the Internet
3. Internet Research Task Force (IRTF) - concerned with ongoing research

1. The Structure of the Internet
   gateway(router) is used to relay messages between subnetworks {receives a PDU and routes it to the next gateway or into the local network} [should work with any kind of network]
2. The Internet Layers
   

   Application Services

   Service Provider Protocol (TCP)

   Internetworking (IP)

   Subnetworks

3. Internetwork Problems
   1. different sizes of datagrams (requires segmentation, etc.)
   2. different addressing methods
   3. different forms of encryption
   4. different networks' tolerance for timing
   5. slow or inefficient gateways
   6. network management / troubleshooting information

1. name - specific identification of a machine, user or an application
2. address - physical or logical location in a network
3. route - how to get a datagram to the address
4. name server - resolves the address and route from the name

1. Subnetwork Addressing
   1. Physical Address (Media access control-MAC Address) [Ethernet uses 48 bits] {IEEE has taken over the role of assigning addresses from Xerox}
      

      1 bit	1 bit	22 bits	24 bits
      I/G	U/L	IEEE Assigned Subnetwork Address	Locally Assigned Physical Address
      0=Individual 1=Group	0=Universal 1=Local

   2. Data Link Address (LSAP - link service access point)
   3. Ethernet Frames
      

      Preamble	Receiver Address	Sender Address	Type	Data	CRC
      64 bits	48 bits	48 bits	16 bits	variable	32 bits

ex. What kind of address is 192.132.89.65?

1. Mapping Types
   • 2 - entry invalid
   • 3 - mapping can change
   • 4 - static
   • 1 - none of the above
   
   [Note: if there is no entry in the ARP cache table, then an ARP Request is broadcast; other ARP caches may use this information to update their own cache]
   

   Hardware Type(16 bits)
   Protocol Type(16 bits)
   Hardware Address Length	Protocol Address Length
   Opcode (16 bits)
   Sender Hardware Address
   Sender IP Address
   Recipient Hardware Address
   Recipient IP Address

   
   
2. The Hardware Type Field
   

   Type	Description
   1	Ethernet
   2	Experimental Ethernet
   3	X.25
   4	Proteon ProNET (Token Ring)
   5	Chaos
   6	IEEE 802.x
   7	ARCnet

   
   
3. The Protocol Type Field
   

   Decimal	Description
   2048	Internet Protocol (IP)
   2049	X.75
   2054	ARP
   32773	HP Probe
   32823	AppleTalk

   
   

• If two or more "networks" with the same network address are connected by a gateway (bridge), the bridge contains a modified ARP (Proxy ARP or Promiscuous ARP) that contains entries from both networks
• if a computer does not know its own IP address, it uses Reverse ARP (RARP) to request the IP address from a RARP Server