CS305 Computer Network course project Reliable Data Transfer in SUSTech 2020-Fall, The description document is at CS305_Project
.
├── code
│ ├── client.py
│ ├── network.py
│ ├── rdt.py
│ ├── server.py
│ ├── USocket.py
│ └── utils.py
├── doc
│ ├── code_org
│ │ ├── network.py
│ │ ├── rdt.py
│ │ └── USocket.py
│ └── CS305_Project.pdf
├── image
│ ├── RDT_Socket.jpg
│ ├── RDT_Socket_Peer.jpg
│ ├── Receive_Window.jpg
│ └── Receive_Window_rollback.jpg
├── LICENSE
└── README.md
Run the python program code in the directory ./code, python version recommended 3.6+
Use default parameters
python network.py
python server.py
python client.pyIt is the same as the follow
python network.py -buf 50000 -loss 0.1 -delay 0 -corrupt 0.00001
python server.py -debug 1
python client.py -file ../LICENSE -debug 1Note:
- Use multiple clients, please run python client.py multiple times
- network.py is used to imitate routers, forward segment
- Parameters:
- rate: limit bandwidth, unit Byte/s, default is None, None means no rate limit
- buf: router buffer size, unit byte
- loss: segment loss rate
- delay: link delay, unit byte/s
- corrupt: segment corrupt rate
- debug: debug model, 1 means active, 0 means closed
- file: file that need to be transferred by the client
- Cumulative Acknowledgement
- Fast retransmission
- Timeout retransmission
- Congestion Control
- Full duplex reliable data transmission
- Multiple clients connect to one server at the same time
- Support one-time transmission of large files (The rollback of seq_num is handled)
Format:
0 1 2 3 4 5 6 7 8 9 a b c d e f
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| Source port # |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| Dest port # |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| Sequence number |
| |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| Acknowledgment number |
| |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| Header length |ACK|RST|SYN|FIN| Unused |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| Checksum |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| |
/ Options /
/ /
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| |
/ Payload /
/ /
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
Flags:
- HEADER LENGTH Header length, unit in word
- ACK Acknowledge
- RST Reset
- SYN Synchronize
- FIN Finish
Ranges:
- Source port 0 - 65535
- Dest port 0 - 65535
- Head Length 16 - 60 bytes
- Sequence Number 0 - 4294967296 bytes
- Acknowledgement Number 0 - 4294967296 bytes
Checksum Algorithm: 16 bit one's complement of the one's complement sum
ref RFC 793
Options:
Kind: 5
Length: Variable
+--------+--------+
| Kind=5 | Length |
+--------+--------+--------+--------+
| Left Edge of 1st Block |
+--------+--------+--------+--------+
| Right Edge of 1st Block |
+--------+--------+--------+--------+
| |
/ . . . /
| |
+--------+--------+--------+--------+
| Left Edge of nth Block |
+--------+--------+--------+--------+
| Right Edge of nth Block |
+--------+--------+--------+--------+
+--------+
| | 1 Byte
+--------+
Field:
- Kind Optional types
- Length The length of this option, in bytes
- Left Edge of nth Block The left byte range of retransmission requirements
- Right Edge of nth Block The right range of bytes of data to be retransmitted
Block:
- Maximum number 5
Function:
- Carry the data sequence number range (in bytes) that requires peer retransmission
ref RFC 2883
Fig. 1 RDT Socket
Fig. 2 RDT Socket Peer
RDT Socket Client
- Data sending and receiving is realized through the interface provided by USocket.
RDT Socket Server
- RDT socket calls the function listen() to become a server, at this time, a listen socket and a data center will be generated.
- Data center distribute the data correctly, the data comes from each peer or network, and the destination is the network or the corresponding peer.
- Listen socket receive the connection request sent by the client.
- When the server successfully establishes a connection with a client, a new peer will be generated inside the server to interact with the client.
Most of the techniques in RDT Socket Peer module refer to Kurose, James F., and Keith W. Ross. Computer Networking: A Top-Down Approach. 2007.
Receive module use priority queue to
- Cache the information of received segment(sequence number and data), sequence num is the key to sorting
- Obtain the range of data sequence numbers that are not received to construct segment filed option 5
- Merge adjacent data in a scattered range of sequence numbers
Fig. 3 Receive window
In order to deal with receive window rollback, a sub priority queue is used to temporarily store the segment information.
Fig. 4 Receive window (rollback)
