Chpt 57 - Packet Switching and Routers

What is packet switching

A method of communicating packets of data across a network on which other similar communications are happening simultaneously????What is the benefit of packet switching

Sizes can be fixed or variable????What sections do each packet contain

Header, payload, trailer????What does the header of a data packet contain

Protocols being used

Number of packet in the sequence

The time to live / hop limit (after which point the data packet expires and is discarded)????What does the payload of a data packet contain

The actual data being sent????What does the trailer section of the data packet contain

They can be used to detect transmission errors????How do checksums and CRCs work

Calculate a hash total based on data in packet and attach it to packet

CRC checksum is recalculated for each packet upon receipt. A match indicates the data has not changed

If CRC totals differ, packet is refused and new copy is requested from sender????What happens to data packets upon receipt

They are assembled in the correct order + the data is extracted????What are routers used for

Commonly LANs or WANs, or a LAN and its ISP's network????What is hopping?

The act of traversing between one router and the next across a network????How does a router direct data packets

A routing algorithm is used to find the optimum route. A shortest path algorithm used in routing is Dijkstra's algorithm????Why must the IP address of a router's Internet-facing port be registered with an Internet registry?

Because it must be globally unique on the Internet, and registration ensures no two devices use the same public IP address, avoiding conflicts in data routing.????When is a gateway used

It is otherwise similar to a router????How does a gateway handle data packets

It strips all the header data, leaving only the raw data

A new header data is added in the format of the new network

The gateway then sends the packet on its way again (in similar way to routers)????