CompE 560 Intro

What are the two types of network connections?

Point-to-point and multipoint

What are the four basic topologies we have learned? What are their advantages and disadvantages?

• Mesh: robust to failures/fault, difficult to install and configure

• Star: easy to modify and troubleshoot, expensive to install and use, whole network fails if the hub fails 

• Bus: cost effective, easy to expand, whole network fails if the cable fails, performance decrease when network traffic is heavy or the number of nodes increases

• Ring: cheap to install and expand, difficult to troubleshot, adding/deleting nodes or node failures will disturb the network

What are PAN, LAN, MAN, WAN, internet, and Internet?

• PAN:  connect devices over the range of a person, e.g., wireless network that connects a computer with its peripherals

• LAN: operate within and nearby a single building like a home, office or factory

• MAN: covers a city, e.g., cable television networks

• WAN: span a large geographical area, like a country or continent

• internet/internetwork: two or more interconnected networks; a generic term

• Internet: a collaboration of hundreds of thousands of interconnected networks; a global system of interconnected computer systems (from Wiki)

What is TCP/IP protocol suite?

The set or suit of protocols that controls the Internet.

What is the protocol?

It defines the rules that both the sender and receiver and all intermediate devices need to follow to be able to communicate effectively.

How to model the TCP/IP protocol?

Often using a five-layer model, including application, transport, network, data link, physical

What’s the reason for protocol layering?

• Divide up network functionality, so as to simplify the design of the networks

• By layering the protocols, the protocols can be changed without affecting the higher or lower one. 

What is the responsibility of each layer in the TCP/IP suite? What are the protocols used in each layer? What is the addressing methodology used in each layer?

• Application layer: 

  • Responsible for providing services to the user. 

  • Protocols: HTTP (Web surfing), SMTP (Mail delivery), FTP (file transfer), telnet (remote login), etc.

  • Addressing: e.g., URL

• Transport layer:

  • Responsible for the logical delivery of a message between client and server processes

  • Several transport protocols: TCP, UDP, SCTP

  • Addressing: port number

• Network Layer:

  • Responsible for the delivery of individual packets from the source host to the destination host 

  • Protocols: IP and some facilitating protocols (e.g., ARP, address resolution protocol, ICMP, Internet control message protocol)

  • Addressing: IP address

• Data Link Layer

  • Responsible for node-to-node delivery of frame

  • Protocols: Underlying LAN, WAN, and MANs technology, e.g., Ethernet (Both Physical & Data Link layers), PPP (point-to-point protocol 

  • Addressing: link addresses, e.g., MAC/Physical address used in Ethernet

• Physical Layer

  • Responsible for node-to-node delivery of bits 

  • Protocols: e.g., Token Ring, Ethernet. 

  • Addressing: no addressing, just use link addresses

• What are the two data transmission methods? What are their differences?

• Packet switching:

  • Messages are broken into packets

  • Each packet may take a separate path

  • Store-and-forward: entire packet must arrive at router before it can be transmitted on to the next link

  • Assume one router in between source and destination

  • To transmit a L-bit packet into the link at R bps, it takes L/R seconds. 

  • End-to-end delay  = 2L/R (assuming no propagation and other delay)

  • In general, sending one packet from source to destination over a path consisting of N links each of rate R, the end-to-end delay is NL/R

  • Circuit switching:

    • A dedicated connection, called a circuit, is always available between two end systems 

    • Disadvantage: underutilization of link capacity

What is the Internet?

• All edge devices are called hosts/end systems

• End systems are connected together by a network of communication links and packet switches 

  • Two most prominent types of packet switch in today’s Internet are routers and link-layer switches

  • Link-layer switches are typically used in access networks

    • Access network: the network that physically connects an end system to the first router (also known as the edge router)

  • Routers are typically used in the network core 

    • The network core is the mesh of packet switches and links that interconnects the Internet’s end systems 

• End systems access the Internet through Internet Service Providers (ISPs)

• End systems, packet switches and other pieces of the Internet run protocols