Internet Protocol Stack

Question 1

Abstraction in the Internet

Answer 1

Abstraction means hiding complex details and showing only what’s necessary

Question 2

Benefits of Protocol Layering

Answer 2

Structure:
– Does not specify an implementation
– Instead, tells us how to organize
functionality →Interoperability
* Modularity
– Eases maintenance, updating of system– Allows identification, relationship of
complex system’s pieces
* Flexibility
– Reuse of code across the network
* Extensibility
– Module implementations may change

Question 3

1.Application layer

Answer 3

Service Physical– Whatever we want :)
* Interface– Whatever you want :D
* Protocol– Whatever you want ;)
* Examples:– File Transfer (FTP)– World Wide Web (HTTP)– Email (SMTP)– Directory Services (DNS

Question 4

2. Transport Layer

Answer 4

Service:
-Moves data between applications
Multiplexing/demultiplexing
– Congestion control
– Reliable, in-order delivery

Interface
– Send message to a destination

Protocol
– Port numbers
– Reliability/error correction
– Flow-control information

• Examples:
  – Transmission Control Protocol (TCP) -reliable
  – User Datagram Protocol (UDP)-fast

Question 5

3.Network layer

Answer 5

Service:
Delivers packets across the network
– Handle fragmentation/reassembly– Packet scheduling
– Buffer management

Interface – Send a packet to a specific destination

Protocol
– Define globally unique addresses
– Maintain routing tables

• Example: Internet Protocol (IP), IPv6

Question 6

Data Link Layer

Answer 6

Service:
Moves data between devices on the same network.
Data framing: boundaries between packets
– Media access control (MAC)
– Per-hop reliability and flow-control

Interface
– Send one packet between two hosts
connected to the same media

Protocol
– Physical addressing (e.g. MAC address)
Examples:
– Ethernet
– Wifi
– DOCSI

Question 7

Physical Layer

Answer 7

Service:
- Moves information between two systems connected to a physical link

Interface
– Specifies how to send one bit

Protocol
– Encoding scheme for one bit
– Voltage levels
– Timing of signals

• Examples:
  – coaxial cable
  – fiber optics
  – radio frequency transmitters
  – Twisted pair
  – Infrared (IR

Question 8

The ISO/OSI model

Answer 8

• Presentation: allow applications to
  interpret meaning of data, e.g.,
  encryption, compression, machine
  specific conventions
• Session: synchronization, checkpointing,
  recovery of data exchange

is a part of the layer and used only when its needed

Question 9

Encapsulation

Answer 9

How does data move through the layers?
- Each layer processes and removes the corresponding header/trailer

Question 10

Layering sometimes can be harmful

Answer 10

• Lower performance due to data and processing overhead
  added by protocol headers
  -The same functionality may be duplicated by different layers
  (e.g. error detection)