Midterm Review
These slides contain 90% recycled content.
Problem 1: Network Address Translation
Src: 192.168.4.56:2410
Dst: 4.3.2.1:80
Src: 128.32.131.210:80
Dst: 74.125.224.50:2500
• Could the packet leaving A have the wrong source address?
• Wrong destination address?
?
Problem 1: Network Address Translation
NAT 2
192.168.4.56:2410
4.3.2.174.125.224.50
128.32.131.210:80
Src: 192.168.4.56:2410
Dst: 4.3.2.1:80Src: 128.32.131.210:80
Dst: 74.125.224.50:2500
NAT 1Packet
leaving A
Packet leaving B
Packet leaving NAT 1?
Packet leaving NAT 2?
Packet leaving A Packet leaving B
Problem 3: Learning Switch
P1
P2
P3
P4
5
E→A
D→A
C→A
A→B
B→E
E→B
D→A
C→BEB
AE
C
D
A F
E
D
B
C
3
1 3
1
4
7
35
1
Problem 4ii: Routing [option 1]
A F
E
D
B
C
3
1 3
1
4
7
35
1
Problem 4ii: Routing [option 2]
A F
E
D
B
C
3
1 3
1
4
7
35
1
A F
E
D
B
C
3
1 3
1
4
7
35
1
Problem 5: Packet Transmission
• FTP: 1 bit per 10 seconds– Apartment is 300 meters away
• RTP: 256GB flash drive, 5 minutes each way
THIS QUESTION IS GOING TO BE
– WAIT FOR IT –
END-TO-END DELAYS
Topics
• Following slides list some points for discussion, taken from lecture slides.
• Not deliberately mid-term related
• Haven’t written new questions– Want your questions!
10. IP Addressing and Forwarding
• Fragmentation• IPv4 and IPv6 Header Comparison• Security analysis: sender• Addressing: Layer 2 vs. 3
– Scalability (State, Churn): aggregation– Hierarchical addressing (network:host) [S6 P1]
– Classful– CIDR [S6 P1]
IP Header: Security analysis4-bit
Version
4-bitHeaderLength
8-bitType of Service
(TOS)16-bit Total Length (Bytes)
16-bit Identification3-bitFlags 13-bit Fragment Offset
8-bit Time to Live (TTL) 8-bit Protocol 16-bit Header Checksum
32-bit Source IP Address
32-bit Destination IP Address
Options (if any)
Payload
Slide 49, Lecture 9; Slides 19-31, Lecture 10
EvasionAmbiguityDatagram limitState-holding
11. Forwarding
• Dealing with address scarcity– Dynamic Host Configuration Protocol [S6 P2]
– Network Address Translation [S6 P2, S7 P1]
• Address aggregation [S6 P1]
• Longest prefix match [S6 P1]
12. Transport and TCP
• Role of transport layer• Sliding window• TCP Header• Three-Way Handshake• Normal Termination, One Side At A Time• Abrupt Termination• Retransmission Timeout (RTO)
Role of transport layer
• De-multiplexing
• Corruption
• Translating between byte-streams and packets• Reliability• Not overloading receiver• Not overloading network• “Connection” set-up & tear-down
Slide 20, Lecture 12
TCP Header
Slide 72, Lecture 12
Source port Destination port
Sequence number
Acknowledgment
Advertised windowHdrLen Flags0
Checksum Urgent pointer
Options (variable)
Data
Flags: SYNACKFINRSTPSHURG