Skip to content

AEiE0904 Data communication switching techniques

Taxonomy of switched networks

Packetization enables statistical multiplexing: packets from multiple bursty users share link capacity on demand instead of reserving one end-to-end circuit for each user.

Network type Setup needed Addressing style Core cue
Circuit-switched Yes Endpoints identified before transfer Dedicated path
Datagram network No dedicated setup Each packet carries destination address Independent packet routing
Virtual-circuit network Yes or logical setup Packets carry VC identifier Logical path with packet transfer

Circuit-switched network phases

Three classic phases:

  1. Connection establishment.
  2. Data transfer.

  3. Connection release.

  4. Resources are reserved during the connection.

  5. Delay is predictable after setup.

Datagram network

  • Each packet is routed independently.
  • Each packet typically carries the full destination address.
  • Packets from the same source to the same destination may take different paths.
  • Packet order is not guaranteed by the network layer alone.

Virtual-circuit network

  • A logical route is set up first.
  • Packets carry a short VC identifier instead of full destination processing at each hop.
  • Order is usually preserved within one VC.
  • X.25, Frame Relay, and ATM are common historical examples in broader study.

Routing table and destination address

  • Datagram routers use a routing table keyed by destination network information.
  • Longest-prefix matching is the common IP interpretation in modern packet routing.
  • A destination address identifies where the packet should be delivered.
  • In VC systems, forwarding often uses incoming-interface plus VC identifier rather than full destination each time.

ISDN services

Service type Idea
Bearer service Pure transport capability provided by network
Teleservice End-to-end communication service such as telephony
Supplementary service Extra features such as call forwarding
  • The exam often uses ISDN as a classification question rather than a detailed protocol question.

Spread spectrum modulation

  • Spread spectrum intentionally uses bandwidth wider than the minimum needed.
  • It improves resistance to interference, jamming, and interception.
Type Distinguishing idea
DSSS Multiply by high-rate spreading code
FHSS Hop carrier among frequencies according to pattern

Multiple access techniques

Technique Resource separated by
FDMA Frequency
TDMA Time slots
CDMA Code
OFDMA Orthogonal subcarriers
  • Multiple access is about many users sharing the medium.
  • Multiplexing is about combining signals, while multiple access is about allocating users or channels; the exam may use them closely but not interchangeably.

Recognition cues for data communication switching techniques

  • "Packets routed independently" means datagram network.
  • "Logical path established before packet transfer" means virtual circuit.
  • "Dedicated path and setup phase" means circuit switching.
  • "Spreading code" points to DSSS or CDMA-style operation.

Common traps in data communication switching techniques

  • Virtual circuit is still packet switching, not circuit switching.
  • Circuit switching reserves path resources; datagram switching does not.
  • ISDN service types are not the same as channel types.
  • Multiple access and spread spectrum are related but separate classification axes.

One-step examples for data communication switching techniques

  • Telephone PSTN is the classic circuit-switch example.
  • IP forwarding without connection setup is the classic datagram example.
  • An ATM-like label-switched path behaves like a virtual circuit.

Data-communication-switching revision box

Circuit switching has setup, transfer, and release. Datagram packets are independent and carry destination addressing. Virtual circuits are packet based but path oriented. DSSS and FHSS are spread-spectrum methods. FDMA, TDMA, and CDMA separate users by resource type.