TCP/IP protocol suites 1

 

Learning Outcomes:

• Know the simple concept of layering in a Transmission Control Protocol/Internet Protocol (TCP/IP) reference model.
• The basic concept of data encapsulation across layers should be introduced.
• Explain the functions of TCP/IP.
  
  

TCP/IP protocol suite

TCP/IP protocol suite is a reference model with sets of protocols used in the internet/computer networks.

Layers	Purposes	Examples of protocols	Address schemes
Application layer	Provide user services	DNS, FTP, HTTP	-
Transport layer	Host-to-host connectivity	TCP, UDP	Port numbers
Internet layer	Host addressing, packet routing	IPv4, IPv6, IPsec	IP addresses
Host-to-network layer	Related to hardware connecting to the network e.g. topology, physical medium	MAC	MAC addresses

 Major function: connect host to internet and transmit data over networks.

Communication protocols: exchange rules in an agreed-upon format.

Encapsulation: When data segment goes through each layer(from higher to lower), additional information are included in the data segment as header +/- trailer. (Details will be covered in data packets later)

Decapsulation: When the data packet arrives its destination, it goes from the lower layer to higher. The additional information(header/trailer) will be used and removed by the relevant layer, then the decapsulated packet will be directed to the higher layer.

Relevant past paper:

DSE ICT Elect B(SP-2017):  SP 2b, diii. 2012 2a.

CE CIT(2005-2011): 2005 2a, 3d.

AS CA(2000-2013): 2008 10b.

 

TCP and UDP

Transmission Control Protocol (TCP) features:

• Reliable: the sender is notified whether the delivery of data packets is successful or not.
• Connection oriented: Establish connection before sending data.
• Reorder the received data packets into correct order.
• Error checking mechanism.

Key point: when completeness of data packet is important.

User Datagram Protocol (UDP) features:

• Unreliable: No acknowledgement of successful/unsuccessful data packet. It uses internet protocol which provides best effort delivery (but not guaranteed). (i.e. both UDP and IP are unreliable)
• Connectionless: No connection establishment
• No error checking.
• All of the above reduces overhead.

Key point: when timely transmission is important and few data packet loss is not important.

Programs using UDP: DHCP, DNS, VoIP (Voice over IP) service

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  2012 2b. 2013 2d.

 

Port number:

Port numbers are used by TCP or UDP to direct the incoming network traffic to corresponding protocols or applications. E.g. port number 80 is used by HTTP.

Three categories of port number:

• 0-1023: well-known ports
• 1024-49151: registered ports
• 49152-65535: dynamic ports

Port number is “borrowed” by Network Address Translation (NAT) for IP addressing. (see next section)

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  2013 1ai.

CE CIT(2005-2011): 2008 2f. 2009 4c.

MAC addresses:

MAC stands for Media Access Control. MAC address, also known as physical address, is a unique number assigned, usually by manufacturer, to a network interface. It is used as an identifier.

Relevant past paper:

AS CA(2000-2013):  2010 9ci.