Tutorials Computer Networks (CN) Year 1 (2022/2023) Computer Science and Engineering at TU Delft Tutorials 1 Error Detection 2 Error Correction and Control 3 Network Layer 4 Transport Layer (1) 5 Transport Layer & Application Layer 6 Security
Tutorial 1 - Error Detection
1 Parity bits
2 Parity words
3 Checksums
4 Cyclic Redundancy Checks
Tutorial 2 - Error Correction and Control
1 Parity blocks
2 Hamming codes
3 Sliding window protocol
Tutorial 3 - The Network Layer
1 Distance Vector Routing
2 Link State Routing
3 CIDR
Tutorial 4 - The Transport Layer 1
1 TCP Sequence Numbers
2 Forbidden Region
Tutorial 5 - Transport Layer & Application Layer
1 Transport Layer
2 Application Layer
Tutorial 6 - Security
1 S-box
2 P-box
3 RSA Encryption
4 RSA Decryption
,Tutorial 1 - Error Detection
1 Parity bits
1.1 The following bit strings are received messages with a parity bit added. Assuming an
even parity, which of them are guaranteed to be wrong?
Method 1 - Check if number of 1s in received messages is even
Method 2 - Consider message without parity bit, compute parity bit, and check if it fits
1.2 In the previous question, you detected an error with one or more messages. Can you (as
a receiver) determine the correct version of these message(s)?
No, parity checks only detect errors but cannot correct them since we don’t know where the
error occurred
1.3 In the first question, we saw that the parity bit method could not detect an error with
some messages. Can we be sure that these messages were correctly transmitted?
No, we cannot be 100% sure. Parity bits with even parity cannot detect errors that flip an
even number of bits. For example, if the sent bit stream is 1111 0000 0000(2) and the
received bit stream is 1111 1111 1111(2), the error is not detected because of the even
number of bit flips (8 of them)
, 2 Parity words
A sender and receiver communicate by a protocol which uses parity words for error
detection. Both know that the data block is a 6 × 8 matrix and the protocol uses even parity.
The receiver receives the following message:
a Does the receiver find any error?
Add the columns together and look at the parity
No, the receiver can not find an error
b Did the receiver receive the bit sequence correctly?
The receiver cannot be sure about the correctness of the bit sequence. For example, the bits
shown in squares may have been flipped
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller liekesanders. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $3.45. You're not tied to anything after your purchase.
