TCPIP: overview

1
TCP/IP overview

• Standards originally by the U.S. Department of
  Defense
• Newer standards by Internet Activities Board
  (IAB)
• Is in 'competition' with OSI
• TCP/IP is a mature, highly functional set of
  protocols
• OSI is evolving and actual protocols have only
  recently emerged
• Has grown significantly over the years
• Often considered an 'interim' step to OSI
• But growth makes it a viable architecture in its
  own right
• Is the basis for Internet communication

2
TCP/IP layers I

• Network access
• OSI equivalent physical, data link, network
  (partial)
• Function provides access to communications
  networks
• Protocols existing (non-TCP/IP) protocols such
  as 802.3, 802.5, X.25
• Internet
• OSI equivalent network (partial)
• Function routing functions implemented in
  hosts, routers
• Protocols internet protocol (IP)

3
TCP/IP layers II

• Host-to-host
• OSI equivalent transport, session (partial)
• Function reliability functions, traffic
  management
• Protocols transmission control protocol (TCP),
  user datagram protocol (UDP)
• Process
• OSI equivalent session (partial), presentation,
  application
• Function protocols to support applications
• Protocols SMTP. FTP, Telnet

4
TCP/IP layers
5
TCP/IP components

• TCP/IP assumes existence of multiple subnetworks
• Network access protocol (e.g., ethernet) connects
  computer to subnetwork or router
• IP is implemented on all hosts and routers
• Acts as a relay to move blocks of data from host
  to host, through one or more routers
• TCP is implemented on all hosts (not on routers)
• Keeps track of blocks of data to ensure reliable
  delivery to appropriate applications
• Each process has a unique address IP address and
  process port

6
TCP/IP communication example I

• Process on port 1 at host A needs to send a
  message to process on port 3 at host B request
  sent to process layer
• Process layer hands message to TCP with
  destination address, port
• TCP breaks message into TCP segments, each with
  destination port, sequence number of segment, and
  checksum/CRC
• TCP hands segment to IP with destination address
  (not port)
• IP adds destination address to segment to form an
  IP datagram
• IP hands datagram to network access protocol with
  address of intermediate router or host

7
TCP/IP communication example II

• Network access protocol adds information for
  transportation over subnetwork
• Sends packet to intermediate router or host
• Intermediate router or host strips away packet
  header, reads destination host address, adds
  address of next hop to form a new IP datagram
• Intermediate router or host hands datagram to
  network access protocol as above
• At final destination host, all headers are
  stripped and data sent upwards to IP, TCP, and
  process layer
• Process layer sends message to application

8
IP addressing current approach

• Current IP version (IPv4) uses 32-bit addresses
• Class A first octet fixed addresses start with
  1-127
• About 16,775,000 (224) addresses per user 127
  such groups of addresses, all assigned/reserved
• Class B first 2 octets fixed addresses start
  with 128-191
• About 65,500 (216) addresses per user about
  16,000 such groups of addresses, about 80
  assigned/reserved
• Class C first 3 octets fixed addressed start
  with 192-223
• 254 addresses per user (address cannot end in 0
  or 255) 2 million such groups of addresses, 30
  assigned/reserved
• Class D and Class E are special purpose not
  assigned

9
IP addressing developments

• Clearly addresses are running out quickly
• Even though IPv4 provides over 1 billion
  addresses, fact that they are assigned in sets
  limits number of addresses
• Also, multiple future applications will need IP
  addresses
• Solution is new IPv6
• 128-bit addresses
• Gives 3.2 ? 1038 possible addresses
• Also provides other improvements in packet
  headers
• IPv4 has 192-bit header, IPv6 has 320-bit header
• Overall, a simpler packet structure than IPv4
• New version of TCP based on IPv6 capabilities is
  also under development

10
More about addressing

• Each computer has multiple addresses for TCP/IP
  access
• Each address is used by a different layer
• Application layer mgmt.ucalgary.ca (DNS address)
• Optional address may have more than one
• Network layer 136.159.191.92 (IP address)
• Necessary for Internet access
• Data link layer 00-0C-00-F5-03-5A (Ethernet
  address)
• Necessary to access the network
• Static and dynamic addressing
• Data link layer address is on network card
  (static)
• Network layer address assigned by software
• May be in configuration file on computer (static)
• May be assigned when connecting to network
  (dynamic)
• Bootstrap protocol (bootp) Dynamic Host Control
  Protocol (DHCP)
• Computer uses data link address to contact
  server, obtain address

11
Subnets
Example 1 Subnet mask is 255.255.255.0
11111111.11111111.11111111.00000000 IP
addresses 136.159.192.127 10001000.10011111.1100
0000.01111111 136.159.192.129 10001000.10011111.1
1000000.10000001 The two stations are on the same
subnet. Example 2 Subnet mask
is 255.255.255.128 11111111.11111111.11111111.
10000000 IP addresses 136.159.192.127 10001000.1
0011111.11000000.01111111 136.159.192.129 1000100
0.10011111.11000000.10000001 The two stations are
now on different subnets.

• Networks that are separated for different
  purposes
• Subnet masks used to specify local network