Conversions and Formulas

Question 1

Convert from Hex to Decimal.

Answer 1

• Hex is base16
• Example:
  
  • Take the hex number 7DE and change each digit to its decimal equivalent
    
    • 7 = 7
    • D = 13
    • E = 14
  • Multiply every digit with 16 power of digit location
  • 7DE is a hex number
  • ​7DE = (7 * 16²) + (13 * 16¹⁾ + (14 * 16⁰)
  • 7DE = (7 * 256) + (13 * 16) + (14 * 1)
  • 7DE = 1792 + 208 + 14
  • 7DE = 2014 (in decimal number)

Question 2

QOS - convert AF value to DSCP

Answer 2

• The formula is 8(x) + 2(y) where x is the first digit of the AF value and y is the second.
• Example:
  
  • AF41
  • AF41 = (8 x 4) + (2 x 1)
  • AF41 = 32 + 2
  • AF41 = DSCP 34

Question 3

Formula to calculate Tc

Answer 3

(Bc [bits] / CIR [bps]) × 1000

Question 4

Formula to calculate Bc

Answer 4

CIR × (Tc / 1000).

Question 5

What is the formula to find the number of Tc’s in 1 second?

Answer 5

1000 ms / Tc[ms]

Question 6

Formula to determine how many packets conform within each Tc?

Answer 6

Bc / packet size in bits (rounded down)

Question 7

What is the formula to find out how many packets would be sent in 1 second?

Answer 7

Number of packets that conform within each Tc × Tc’s per second

Question 8

Formula to determine the CIR

Answer 8

Packets per second × Packet size in bits

Question 9

Formula to calculate the time interval it would take for 1000 packets to be sent at interface line rate?

Answer 9

(Bc [bits] / Interface speed [bps]) × 1000