Download Accompanying slides for Project 3

CS415
Minithreads Project 3
Overview
Adrian Bozdog (Adi)
[email protected]
What you have to do
 Implement unreliable communication
 Simulate IP/UDP protocol
 No UDP check-sum
 No UDP fragmentation
 There is an IP layer that sends and receives
messages (see network.c)
 Start using Jornada systems
 Run Project 3 on both PC desktops and
Jornada systems
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Networking pseudo-device
(1)
 It allows communication between minithreads
systems
 Does not control which thread processes a
received packet
 Interrupt-driven implementation
 Network_handler




executed for each received packet
Uses the stack of the current thread
It should finish as soon as possible
Initialized using network_initialize function
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Networking pseudo-device
(2)
 Network_handler receives a structure:
 typedef struct {
 network_address_t addr; - sender
 char buffer[MAX_NETWORK_PKT_SIZE]; - the body of
entire message
 int size; - the length of the entire message
 } network_interrupt_arg_t;
 Call Network_initialize function
 After clock_initialize()
 Before enabling interrupts and running threads
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Networking functions
 Network_send_pkt – sends a packet
 Destination
 Header (body, length)
 Data (body,length)
 Header:
 Extra information
 About the sender
 About the receiver
 As small as possible
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Minimsg Layer
 Identifies the end-points of the
communication (ports)
 The sender assembles the header used to
identifies the endpoints
 The receiver
 examines the header
 Identifies destination
 Enqueues the packet in the right place
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Minimsg Functions
 Minimsg_send:
 Non-blocking
 Parameters:
 local and remote ports
 The message and its length
 Appends the header to the message
 Sends the entire data using network_send
 Minimsg_receive:
 Blocks the thread until it receives a message on
the specified port
 Receives information about the remote port –
used to reply
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Miniports
 Data structures that represents endpoints
 Local ports:
 Usually, used for listening
 Remote ports:
 Created when a packet is received
 Bound to a sending “remote” port
 Allows the receiver to reply
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Miniports Example
 Ports 2,3 – local ports
 A,B - Threads
 Sender A sends a message to Receiver B
2
A
Sender
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B
Receiver
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Miniports Example
 Creates the remote port 100
 B receives the message;
 Minithreads system creates the remote
port 100
2
A
Sender
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100
B
Receiver
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Miniports Example
 B replies to A
 B uses the remote port as the destination of
the message; the message is relayed to the
sending port
2
A
Sender
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100
B
Receiver
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Miniports – hints
 Local communication
 Be aware of miniport_destroy function called by
the receiver
 Remote_miniport – pointer to the local port
 Miniport_send implemented based on the “remote
port”
 Miniports




Identified by numbers
Assigned them successive numbers
Local miniports – starts from 0
Remote miniports – starts from 32768
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Implementation hints
 Do not add unnecessary data to the header
(ex: header length)
 Include the address of the sender (used by the
routing protocol later)
 Port operations must be O(1)
 Do not waste resources
 Remote miniports are destroyed by the
application
 Build other test cases
 Network_initialize returns the ip address of
the machine
 Due Date: March 3, 12 pm
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Jornada systems
 Every group must have at least a
Jornada system
 Come to my office (Upson 5152)
 I’ll post an announcement
 You must fill check-out forms
 Information for using Jornada in the
assignment description
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