Tomorrow

1
Tomorrow

• Quality of Service (QoS)
• Security

2
Quality of Service (QoS)

• Throughput Problems and Guarantees
• Congestion
• When too many transmissions are on a network,
  traffic will slow down this is congestion
• Latency
• Latency is the amount of time that packets or
  frames are delayed because of congestion
• Want guarantees of maximum latency
• Throughput
• Throughput is the guaranteed speed in bits per
  second

3
Quality of Service (QoS)

• Reliability Problems and Guarantees
• Availability
• Availability is the percentage of time the
  network is available to users.
• Telephone system has 99.999 availability
• Error Rate
• Error rate is the percentage of bits or messages
  that contain errors
• 3 - 6 of all packets are lost on the Internet

4
Security

• A Growing Problem
• Encryption
• Sender encrypts messages before sending them so
  that anyone intercepting them en route cannot
  read them
• Receiver can decrypt encrypted messages and read
  them

Encryption
Decryption
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5
Security

• Authentication
• Sender of a message must prove their identity
• To thwart impostors who impersonate people
• Access Control
• Prohibits or authorizes access to various
  resources (files, programs, etc.)
• Needs authentication but also more
• Access control lists for resources specify what
  resources the authorized person may use and how
  they may use them