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Resource Reservation (cont’d)
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| bet | 2/12 | | Sana | 26.12.2023 | | Hajmi | 492 Kb. | | #128375 |
Bog'liq qos-f05 - Once a connection is accepted, the host must use only the amount of resources reserved. It may not use more than that.
- What if the host is malicious and attempts to use more network resources than it reserved?
Leaky Bucket - Used in conjunction with resource reservation to police the host’s reservation
- At the host-network interface, allow packets into the network at a constant rate
- Packets may be generated in a bursty manner, but after they pass through the leaky bucket, they enter the network evenly spaced
Leaky Bucket: Analogy Leaky Bucket (cont’d) - The leaky bucket is a “traffic shaper”: It changes the characteristics of packet stream
- Traffic shaping makes more manageable and more predictable
- Usually the network tells the leaky bucket the rate at which it may send packets when the connection begins
- Polices the average rate
Leaky Bucket: Doesn’t allow bursty transmissions - In some cases, we may want to allow short bursts of packets to enter the network without smoothing them out
- For this purpose we use a token bucket, which is a modified leaky bucket
Token Bucket - The bucket holds tokens instead of packets
- Tokens are generated and placed into the token bucket at a constant rate
- When a packet arrives at the token bucket, it is transmitted if there is a token available. Otherwise it is buffered until a token becomes available.
- The token bucket has a fixed size, so when it becomes full, subsequently generated tokens are discarded
Token Bucket - Token Generator
- (Generates a token
- once every T seconds)
Token Bucket vs. Leaky Bucket - Departure time from a leaky bucket
- Leaky bucket rate = 1 packet / 2 time units
- Leaky bucket size = 4 packets
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