1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
|
# $Id$
This directory will contain a simple, small-scale reliable
multicast framework for ACE. The framework is based on the ASX
components of the ACE library: the protocol is implemented as a stack
of interchangeable "modules", each one in charge of a very small task.
For example, one module implements fragmentation and reassembly, other
modules implement retransmission, send ACK and NAK messages, and
maintain receiver membership.
The modules are replaced to achieve different levels of
reliability. For example, the retransmission module can be either the
"Best_Effort", "Semi_Reliable" or "Reliable" implementation. In the
first case no retransmissions are performed, but lost messages are
detected and reported to the receiver. The "Semi_Reliable" case
messages are held for a pre-specified amount of time, and
re-transmited if requested, but it is possible to loose some messages
if multiple re-transmissions fail. As in the "Best_Effort" case the
lost messages are detected and flagged to the application. Finally
in the "Reliable" mode the senders are flowed controlled until enough
messages are successfully transmitted.
In general the stack looks like this:
SENDER:
----------------------------------------------------------------
Buffering : Save lost messages
Retransmission : Retransmit
----------------------------------------------------------------
Fragmentation : Fragment messages in smaller chunks
Reassembly : and ensure that the IOVMAX limit is not
: reached
----------------------------------------------------------------
Tranport : Encapsulate the specific transport media
: such as TCP/IP, ATM, or shared memory
: Demuxes incoming data to the right chain
: Change control messages and data messages
: to the right dynamic types.
----------------------------------------------------------------
RECEIVER:
----------------------------------------------------------------
Lost detection : Detect lost messages and send control
: messages back
----------------------------------------------------------------
Reassembly : Reassemble messages, fragment control
Fragmentation : data
----------------------------------------------------------------
Transport : Group membership, ACT reception,
: handle keep-alive messages...
----------------------------------------------------------------
@@ TODO: Piggybacking...
|
