Networking Protocols

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Networking Protocols
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Link

• http//topicmaps.bond.edu.au/mda/internet/tcpip/_at_/
  users/rho/InTechI/

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OSI Reference Model

• Open System Interconnection (ISO), -1988
• architecture for communicating entities
• 7 protocol layers
• 3 network protocol layers
• 4 application protocol layers

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OSI Reference Model (cont'd)

• physical layer
• link layer
• network layer
• transport layer
• session layer
• presentation layer
• application layer

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Internet Protocol Stack

• OSI layers too heavyweight
• lower
• physical
• link,
• Internet, IP (Internet Protocol), ICMP, IGMP
• TCP, transport control protocol
• UDP, user datagram protocol
• application protocols
• telnet (interactive), HTTP (web), SMTP (mail),
  FTP (file transfer), ....

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IP networking

• IP operation
• IP routing
• IP addresses
• address classes network addresses
• subnetting (masks)
• supernetting (CIDR)

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IP Operation

• packet oriented
• one packet after another, every packet carries
  address
• connectionless
• no context is saved between two packets
• unreliable delivery
• delayed, lost, duplicated, out-of-sequence,
  fragmented
• IP
• fragmentation

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IP Datagram Format

• header
• version
• checksum
• size of data
• source, destination IP address
• TTL, time-to-live
• payload
• data

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IP Routing

• determine next hop based on destination IP
• mapping from destination IP to next hop IP
• routing table
• dynamically updated
• a router is
• special machine (hardware), fast
• host capable of routing (software), flexible

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IP addresses

• IP address
• quadruple of integers 0..255, 32 bit
• identifies a specific host
• in some cases a single IP address can specify
  many hosts
• source and destination
• notation
• dotted decimal 128.130.123.1
• decimal 2156034817

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IP address classes

• problem with IP addresses
• routing table would be huge
• introduction of classes
• Class A starting (binary) with 0xxx
• Class B starting (binary) with 10xx
• Class C starting (binary) with 110x
• Class D starting (binary) with 1110 (multicasts)
• (Dec224-239, video conferencing)
• Class E reserved (Dec 240-254, Experimental
  purpose)

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IP classes network addresses

• Class A first byte determines network
• the rest the host
• NNNNNNNN.nnnnnnnn.nnnnnnnn.nnnnnnnn
• Class B first 2 bytes determine network
• Class C first 3 bytes determine network
• network address
• 140.179.x.x or 140.179.0.0
• only networks are routed, not individual IPs

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Subnetting

• http//james.bond.edu.au/courses/inft12230/043/Lab
  s/week8.html
• splitting an address space
• suborganisations, research, sales, ....
• robbing bits from the host portion
• use those as subnet identifier
• subnet mask
• 32 bit pattern, logical AND with the IP address
• 10nnnnnn.nnnnnnnn.hhhhhhhh.hhhhhhhh
• 11111111.11111111.11110000.00000000

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Subnetting (cont'd)

• subnet mask significant to the closest router
• if network address belongs to
• directly attached network
• use subnet mask to find out which network
• elsif other known network
• use next router out of router table
• else (if completely unknown)
• use default route

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IP Default Routes

• most hosts/router need a default route
• where to send packets when dest network unknown
• default gateway
• 0.0.0.0 -gt 128.130.134.1

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IP Host Routing

• add routes for specific host
• application
• testing, debugging
• security (firewalls)

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IP address space

• early/mid '90s
• strong growth of organisations
• networks were assigned sequentially, not by ISP
• limited number of networks
• class B only 16382 networks of 65534 hosts each
• class C 2097150 networks of 254 hosts each

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IP address space (cont'd)

• Problems
• routing tables grew bigger
• many class A, but organisations did not use them
  fully
• classful system wasted addresses
• Solution
• classless InterDomain Routing (CDIR)
• http//public.pacbell.net/dedicated/cidr.html
• NAT
• organisations hidden behind firewalls

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IP address space

• ISPs did
• recollect networks from customers
• reassigned them subblocks out of their blocks
• companies started using RFC1918 networks NAT
• the bigger the ISP the bigger the blocks
• north america has 198.0.0.0/8
• pacific rim has 202.0.0.0/8

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Nat

• Network address translation is a scheme that
  allows two connected networks to use different
  and incompatible IP addressing schemes. Address
  translation allows hosts on a private internal
  network to transparently communicate with
  destinations on an external network or vice
  versa. NAT also refers to the name of a device
  that performs these functions.

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IPv6

• replacement for the current IPv4
• larger address space
• 128 instead of 32 bit
• every toaster will have IP?
• xxxxxx or 192.168.0.0
• migration issues
• impact on TCP and timing
• impact on application programs
• no single cutover date, will(?) happen gradually

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Transport Layer

• TCP
• connection oriented
• bidirectional 'pipe' defined by the two endpoints
• UDP
• connectionless
• datagram service

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Host Ports

• every communication session on a host has a port
  address
• well-known ports (IANA, RFC1700)
• web, HTTP 80
• proxy, HTTP 8080, 3128
• mail, SMTP 25
• telnet, TELNET 23
• ftp, FTP 2120
• application address is 192.168.13.1480

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User Datagram Protocol (UDP)

• simple, efficient
• no context is stored in the network layers
• connectionless
• faster startup, no connection must be established
• unreliable
• based on IP
• no acknowledgement, no flow control

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Transport Control Protocol (TCP)

• complex
• connection oriented
• virtual circuit between two endpoints
• windowing acknowledgement
• flow control
• Status open, close, send, receive, abort

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Int. Control Msg Protocol (ICMP)

• transports error messages
• time-outs, ....
• these are usually acted on the IP layer or the
  higher layer protocols (TCP or UDP).
• may lead to an error message to the user

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Int. Group Mgmt Protocol (IGMP)

• used for managing Multicast (1N) groups
• joining, leaving such a group
• group status

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Technical Terms

• latency
• delay (in secs) between send and receive
• packet drop
• 's of packets dropped typically
• (full-)duplex, half-duplex, simplex

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Technical Terms

• Internet
• open network of networks, IP based
• Intranet
• private network, often behind a firewall
• mostly IP based
• Extranet
• private network, but using open network
  infrastructure