Queuing Delays and Packet Loss p.51~

• The output buffers play a key role in packet switching

  in addition to the store-and-forward delays, packets suffer output buffer queuing delays

   

   

 

Forwarding Tables and Routing Protocols

• how does the router determine which link it should forward the packet onto? Packet forwarding is actually done in different ways in different types of computer networks.

 

• When a source end system wants to send a packet to a destination end system, the source includes the destination’s IP address in the packet’s header.

 

• When a packet arrives at a router in the network, the router examines a portion of the packet’s destination address and forwards the packet to an adjacent router.

 

• each router has a forwarding table that maps destination addresses (or portions of the destination addresses) to that router’s outbound links

 

1.3.2 Circuit Switching

 

• the path between the sender and receiver maintain connection state for that connection. In the jargon of telephony, this connection is called a circuit.

• the four circuit switches are interconnected by four links. Each of these links has four circuits, so that each link can support four simultaneous connections.

 

 

Multiplexing in Circuit-Switched Networks

• FM radio stations also use FDM to share the frequency spectrum between 88 MHz and 108 MHz, with each station being allocated a specific frequency band.
• Proponents of packet switching have always argued that circuit switching is wasteful because the dedicated circuits are idle during silent periods

 

 

Packet Switching Versus Circuit Switching

 

• Critics of packet switching have often argued that packet switching is not suitable for real-time services because of its variable and unpredictable end-to-end delays

• Proponents of packet switching argue that

        (1) it offers better sharing of transmission capacity than circuit switching

        (2) it is simpler, more efficient, and less costly to implement than circuit switching