Internet Technologies Tutorial 4 Questions
1.
Describe the working principle of the Leaky Bucket Algorithm.
–
Leaky Bucket algorithm is a mechanism that turns and uneven flow of packets
form the user processes inside the host into an even flow of packets onto the
network. The working principle are as follows:
– each host connected to the network has an interface containing a
"leaky bucket” (a queue)
– Packets can arrive at any rate
– Packets are discarded when the bucket overflows.
– Packets depart at a constant rate.
2.
Describe the working principle of the Token Bucket Algorithm. What are the
main differences between Token Bucket Algorithm and Leaky Bucket
Algorithm?
–
In the token bucket algorithm, the leaky bucket holds tokens, generated by a
clock at the rate of one token every DT second. When a packet is to be
transmitted, a token must be captured and destroyed. If there is no token in
the bucket, the algorithm can not transmit any packet. Idle hosts can save up
permission (tokens) to send bursts later. The maximum number of tokens
allowed to be saved is n Token bucket algorithm does not discard packets.
The main differences are:
1. The leaky bucket algorithm does not allow idle hosts to save up
permission to send large bursts later. The token bucket algorithm does
allow saving, up to the maximum size of the bucket, n. This property
means that bursts of up to n packets can be sent at once, allowing some
burstiness in the output stream and giving faster response to sudden
bursts of input.
2. Token bucket algorithm throws away token (i.e., transmission capacity)
when the bucket fills up but never discards packets. In contrast, the
leaky bucket algorithm discards packets when the bucket fills up.
3. Imagine a flow specification that has a maximum packet size of 1000 bytes, a
token bucket rate of 10 million bytes/sec, a token bucket size of 1 million
bytes, and a maximum transmission rate of 50 million bytes/sec. How long
can a burst at maximum speed last?
4. The current standard for IPv6 has no header checksum. What are the
advantages and disadvantages of this approach?
5. The Protocol field used in the IPv4 header is not present in the fixed IPv6
header. Why not?
6. How to encode an IPv4 address in an IPv6 address?
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0000 . . . 0000
FFFF IPv4 Address
80 bits
16 bits 32 bits
Internet Technologies Tutorial 4 Questions
7.
Describe, with suitable diagrams, the general form of an IPv6 datagram with
multiple headers, the format of the IPv6 base header. What are the main
changes introduced by IPv6 comparing with IPv4?
Main changes:
 Larger addresses. The addresses size changes from 32 bits to 128 bits
 Extended Address Hierarchy. IPv6 uses the larger address space to
create additional levels of addressing hierarchy.
 Flexible Header Format.
 Improved Options.
 Provision for protocol extension
 Support for auto-configuration and renumbering
 Support for Resource allocation.
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