Systems and methods for the emulation of TDM circuits over a real-time scheduled packet network
View Patent ↗A system and method to emulate any TDM circuit on a Real-Time Scheduled Packet Network. The TDM circuit can be any serial or parallel bit stream, of any bit rate, and can either be synchronized to the Real-Time Scheduled Packet Network, or can be asynchronous to the network. The present system and method determines the requisite descriptors of a scheduled IP itinerary for any emulated TDM circuit.
1. A method for mapping a Time Domain Multiplexed (TDM) circuit onto a scheduled packet network comprising:
calculating a plurality of groups of appointments per scheduled packet;
calculating for each of said groups of appointments per packet, a plurality of numbers of total appointments per schedule interval;
selecting a specific groups of appointments per scheduled packet;
selecting a specific total number of appointments per schedule interval; and
mapping said TDM circuit to said scheduled network according to said selected number of appointments per scheduled packet and said total number of appointments per schedule interval.
2. The method according to claim 1 wherein said TDM circuit is synchronized to said scheduled packet network.
3. The method according to claim 2 wherein said plurality of numbers of appointments required per schedule interval are calculated according to the following formula:
A=(G×SI)/(NT×T);
wherein
G is the group of appointments that each packet requires;
N T is the number of TDM frames in time interval T; and
SI is the schedule interval in milliseconds.
4. The method according to claim 1 wherein said TDM circuit is asynchronous to said scheduled packet network.
5. The method according to claim 4 wherein said group of appointments per scheduled packet (G) is determined according to the following formula:
G=A/K
wherein A is the total number of appointments required per schedule interval, and
wherein K is the number of packets per schedule interval.
6. The method according to claim 4 wherein said plurality of numbers of appointments required per schedule interval are calculated according to the following formula:
A=K×Roundup(MEPS/Appt_Size);
wherein
K is the number of packets per schedule interval,
MBPS is the maximum expected packet size in bytes,
Appt_Size is the appointment size in bytes and the roundup function rounds up to the nearest integer.
7. The method according to claim 1 further comprising:
determining schedule efficiency for said network for each of a plurality of groups of appointments per scheduled packet and for each of a plurality of total appointments per schedule interval;
determining bandwidth efficiency for said network for each of a plurality of groups of appointments per scheduled packet and for each of a plurality of total appointments per schedule interval; and
wherein said number of groups of appointments per scheduled packet and total number of appointments per schedule interval are selected according to a favorable combination of schedule efficiency and bandwidth efficiency.
8. The method according to claim 7 comprising
determining packetization delay for said network for each of a plurality of groups of appointments per scheduled packet and for each of a plurality of total appointments per schedule interval; and
wherein said number of appointments per scheduled packet and total number of appointments per schedule interval are selected according to a favorable combination of schedule efficiency and bandwidth efficiency and packetization delay.
9. The method according to claim 8 wherein said favorable combination includes a high schedule efficiency, a high bandwidth efficiency and low packetization delay.
10. The method according to claim 8 wherein said TDM circuit is synchronized to said scheduled packet network and said packetization delay is determined using the following formula:
Packetization_Delay=N T ×T;
wherein N T is the number of TDM frames in time interval T.
11. The method according to claim 8 wherein said TDM circuit is asynchronous to said scheduled packet network and said packetization delay is determined according to the following formula:
Packetization_Delay=SI/K;
wherein SI is the schedule interval in milliseconds, and
K is the number of packets per schedule interval.
12. The method according to claim 7 wherein said TDM circuit is synchronized to said scheduled packet network and said schedule efficiency is determined according to the following formula:
Sched_Eff
=
F
T
×
S
I
A
×
Appt_Size
×
T
wherein
F T is the number of bytes per time interval T in milliseconds,
A is the total number of appointments per schedule interval,
Appt_Size is the appointment size in bytes, and
SI is the schedule interval in milliseconds.
13. The method according to claim 7 wherein said TDM circuit is synchronized to said scheduled packet network and said bandwidth efficiency is determined according to the following formula:
BW_Eff
=
N
T
×
F
T
N
T
×
F
T
+
(
Max_I
P_Overhead
)
wherein
NT is the number of TDM frames in time interval T,
FT is the number of bytes per time interval T in milliseconds, and
Max_IP_Overhead represents the maximum total number of packet overhead bytes at or above the IP layer.
14. The method according to claim 7 wherein said TDM circuit is asynchronous to said scheduled packet network and said schedule efficiency is determined according to the following formula:
Sched_Eff
=
TDM_BR
nom
×
S
I
Appt_Size
×
A
wherein
TDM_BR nom is the nominal TDM bit rate,
SI is the schedule interval in milliseconds,
Appt_Size is the appointment size in bytes, and
A is the total number of appointments per schedule interval.
15. The method according to claim 7 wherein said TDM circuit is asynchronous to said scheduled packet network and said bandwidth efficiency is calculated according to the following formula:
BW_Eff
=
TDM_BR
nom
×
S
I
TDM_BR
nom
×
S
I
+
(
Max_I
P_Overhead
+
8
+
K
)
wherein
TDM_BRnom is the nominal TDM bit rate,
Max_IP_Overhead represents the maximum total number of packet overhead bytes at or above the IP layer
SI is the schedule interval in milliseconds, and
K is the number of packets per schedule interval.
16. The method according to claim 1 wherein said plurality of numbers of groups of appointments per scheduled packet are calculated according to the following formula:
G
max
=
Interger
(
Maximum_Packet
_Size
Appt_Size
)
wherein
Maximum_Packet_Size is the maximum packet size in bytes,
Appt_Size is the appointment size in bytes, and
Gmax is the maximum contiguous group of appointments per scheduled packet.
17. A scheduled packet network emulating a time domain multiplexed (TDM) circuit wherein internet protocol (IP) packets are scheduled according to an itinerary of appointments and wherein said itinerary of appointments are configured by
calculating a plurality of groups of appointments per scheduled packet;
calculating for each of said groups of appointments per scheduled packet, a plurality of numbers of total appointments per schedule interval;
selecting a specific number of groups of appointments per scheduled packet;
selecting a specific total number of appointments per schedule interval; and
mapping said TDM circuit to said scheduled network according to said selected number of appointments per scheduled packet and said total number of appointments per schedule interval.
18. The scheduled packet network according to claim 17 wherein said TDM circuit is synchronized to said scheduled packet network.
19. The scheduled packet network according to claim 17 wherein said TDM circuit is asynchronous to said scheduled packet network.
20. The scheduled packet network according to claim 17 wherein said plurality of numbers of groups of appointments per scheduled packet are calculated according to the following formula:
G
max
=
Integer
(
Maximum_Packet
_Size
Appt_Size
)
wherein
Maximum_Packet_Size is the maximum packet size in bytes,
Appt_Size is the appointment size in bytes, and
Gmax is the maximum contiguous group of appointments per scheduled packet.
21. A scheduled packet network emulating a time domain multiplexed (TDM) circuit wherein internet protocol (IP) packets are scheduled according to an itinerary of appointments, said network comprising:
means for calculating a plurality of groups of appointments per scheduled packet;
means for calculating a plurality of numbers of total appointments per schedule interval for each of said groups of appointments per scheduled packet; and
means for mapping said TDM circuit to said scheduled network according to a selected favorable number of appointments per scheduled packet and a selected favorable total number of appointments per schedule interval.
22. The scheduled packet network according to claim 21 wherein said plurality of numbers of groups of appointments per scheduled packet are calculated according to the following formula:
G
max
=
Integer
(
Maximum_Packet
_Size
Appt_Size
)
wherein
Maximum_Packet_Size is the maximum packet size in bytes,
Appt_Size is the appointment size in bytes, and
Gmax is the maximum contiguous group of appointments per scheduled packet.