Title: Network with self regulating quality of service (QoS)
Abstract: A communications system and method for self-regulating quality of service in a communications network are provided which includes measuring the amount of jitter of a first media stream received in a router, comparing the amount of jitter of the first media stream received in the router to the amount of jitter of at least one other media stream received in the router and prioritizing the timing of the transmission of a packet in the first media stream from the router based at least in part on the results of the comparing step. The communication system and method for self regulating quality of service also provide for self-regulating quality of service in a communications network by receiving at a first router a measurement of the amount of jitter associated with the media stream at a third router and prioritizing the timing of the transmission of a packet in the media stream from the first router via a second router toward the third router based at least in part on the amount of jitter associated with the media stream measured at the third router.
Patent Number: 6,977,905 Issued on 12/20/2005 to Shaffer, et al.
| Inventors:
|
Shaffer; Shmuel (Palo Alto, CA);
Rubin; Rami D. (Cupertino, CA)
|
| Assignee:
|
Cisco Technology, Inc. (San Jose, CA)
|
| Appl. No.:
|
873080 |
| Filed:
|
June 1, 2001 |
| Current U.S. Class: |
370/252; 370/352; 370/401; 370/516; 370/519; 370/229; 370/231 |
| Intern'l Class: |
H04J 003/06 |
| Field of Search: |
370/230,252,253,352,400,401,412,516,229,231
|
References Cited [Referenced By]
U.S. Patent Documents
| 5883819 | Mar., 1999 | Abu-Amara et al.
| |
| 5966387 | Oct., 1999 | Cloutier.
| |
| 5996018 | Nov., 1999 | Duault et al.
| |
| 6058114 | May., 2000 | Sethuram et al.
| |
| 6119235 | Sep., 2000 | Vaid et al.
| |
| 6215791 | Apr., 2001 | Kim.
| |
| 6259677 | Jul., 2001 | Jain.
| |
| 6278693 | Aug., 2001 | Aldred et al.
| |
| 6301244 | Oct., 2001 | Huang et al.
| |
| 6377551 | Apr., 2002 | Luo et al.
| |
| 6452950 | Sep., 2002 | Ohlsson et al.
| |
| 6466548 | Oct., 2002 | Fitzgerald.
| |
| 6529499 | Mar., 2003 | Doshi et al.
| |
| 6535567 | Mar., 2003 | Girardeau, Jr.
| |
| 6560230 | May., 2003 | Li et al.
| |
| 6640193 | Oct., 2003 | Kuyel.
| |
| 6707821 | Mar., 2004 | Shaffer et al.
| |
| 6744767 | Jun., 2004 | Chiu et al.
| |
| 6798745 | Sep., 2004 | Feinberg.
| |
| 2002/0039371 | Apr., 2002 | Hedayat et al.
| |
Primary Examiner: Rao; Seema S.
Assistant Examiner: Patel; Jay P.
Attorney, Agent or Firm: Baker Botts L.L.P.
Claims
1. A method for self-regulating quality of service in a communications network, comprising:
measuring an amount of jitter of a first media stream received in a first router;
comparing the amount of jitter of the first media stream received in the first
router to the amount of jitter of at least one other media stream received in the
first router;
receiving at the first router a measurement of the amount of jitter associated
with the first media stream at a second router; and
prioritizing timing of a transmission of a packet of the first media stream from
the first router toward the second router based at least in part on results of
the comparing step and at least in part on the amount of jitter associated with
the first media stream at the second router.
2. The method of claim 1, wherein the packet is a voice packet.
3. The method of claim 1, further comprising storing the measurement of jitter
of the first media stream and the at least one other media stream.
4. The method of claim 1, wherein the step of prioritizing includes optimizing
quality of service.
5. The method of claim 1, wherein the step of prioritizing includes timing the
transmission of the packet from the first media stream before the transmission
of a packet from the at least one other media stream when the first media stream
has a greater amount of jitter than the at least one other media stream.
6. The method of claim 1, wherein the first media stream has traversed through
a plurality of routers, wherein the step of measuring comprises determining a number
of routers through which the packet has traversed and wherein the number of routers
represents the amount of jitter.
7. A method for self-regulating quality of service in a communications network
having a communication path between at least a first router and a third router
via a second router, comprising:
receiving a measurement of an amount of jitter associated with a media stream
at at least the third router; and
prioritizing timing of a transmission of a packet in the media stream from at
least the first router toward at least the third router via the second router based
at least in part on the amount of jitter associated with the media stream at the
third router.
8. The method according to claim 7, wherein the amount of jitter associated with
the media stream at the third router is communicated to the first router.
9. The method according to claim 7, wherein the third router prioritizes the
timing of the transmission of the packet from the first router.
10. The method according to claim 7, further comprising:
measuring the amount of jitter associated with the media stream at the third
router; and
communicating the amount of jitter measured at the third router to the first router.
11. The method according to claim 7, wherein the receiving and prioritizing occur
at a central server.
12. The method of claim 7, wherein the media stream has traversed through a plurality
of routers, wherein the measurement of the amount of jitter comprises a determination
of a number of routers through which the packet has traversed and wherein the number
of routers represents the amount of jitter.
13. A method for self-regulating quality of service in a communications network, comprising:
measuring an amount of jitter of a first media stream received in a first router;
comparing the amount of jitter of the first media stream received in the first
router to the amount of jitter of at least one other media stream received in the
first router;
receiving at the first router a measurement of the amount of jitter associated
with the first media stream at a third router;
prioritizing timing of a transmission of a voice packet in the first media stream
from the first router via a second router toward the third router based at least
in part on results of the comparing step the amount of jitter of the first media
stream to the amount of jitter of at least one other media stream and at least
in part on the amount of jitter associated with the first media stream at the third
router; and
storing the measurement of jitter of the first media stream and the at least
one other voice media stream.
14. The method according to claim 13, further comprising measuring the amount
of jitter associated with the first media stream at the third router that is to
receive the voice packet.
15. The method of claim 13, wherein the step of prioritizing includes optimizing
quality of service.
16. The method of claim 13, wherein the step of prioritizing includes timing
the transmission of the voice packet before the transmission of a voice packet
in the at least one other media stream when the first media stream has a greater
amount of jitter than the at least one other media stream.
17. The method of claim 13, wherein the first media stream has traversed through
a plurality of routers, wherein the step of measuring comprises determining a number
of routers through which the packet has traversed and wherein the number of routers
represents the amount of jitter.
18. A system for self-regulating quality of service in a communications network, comprising:
means for measuring an amount of jitter of a first media stream received in a
first router;
means for comparing the amount of jitter of the first media stream received in
the first router to the amount of jitter of at least one other media stream received
in the first router;
means for receiving at the first router a measurement of the amount of jitter
associated with the first media stream at a second router; and
means for prioritizing the timing of a transmission of a packet in the first
media stream from the first router toward the second router based at least in part
on results of the comparing step and at least in part on the amount of jitter associated
with the first media stream at the second router.
19. A computer readable medium including logic for self-regulating quality of
service in a communications network, the logic operable to:
measure an amount of jitter of a first media stream received in a first router;
compare the amount of jitter of the first media stream received in the first
router to the amount of jitter of at least one other media stream received in the
first router;
receive at the first router a measurement of the amount of jitter associated
with the first media stream at a second router; and
prioritize the timing of a transmission of a packet in the first media stream
from the first router toward the second router based at least in part on results
of the comparing step and at least in part on the amount of jitter associated with
the first media stream at the second router.
20. A system for self-regulating quality of service in a communications network
having a communications path between at least a first router and a third router
via a second router, comprising:
means for receiving a measurement of an amount of jitter associated with a media
stream at the third router; and
means for prioritizing timing of a transmission of a packet in the media stream
from the first router via the second router toward the third router based at least
in part on the amount of jitter associated with the media stream measured at the
third router.
21. A computer readable medium including logic for self-regulating quality of
service in a communications network having a communications path between at least
a first router and a third router via a second router, the logic operable to:
receive a measurement of an amount of jitter associated with a media stream at
a third router; and
prioritize timing of a transmission of a packet in the media stream from a first
router via a second router toward the third router based at least in part on the
amount of jitter associated with the media stream measured at the third router.
22. A method for self-regulating quality of service in a communications network, comprising:
receiving a first measurement of an amount of jitter of a media stream at a first router;
receiving a second measurement of an amount of jitter of the media stream at
a second router;
associating, at a central server, the first measurement with the second measurement
as jitter of the media stream at the first router and the second router, respectively; and
establishing a priority of transmission of a packet of the media stream from
the first router toward the second router at the central server, using the first
measurement with the second measurement.
23. The method of claim 22, further comprising communicating the priority to
the first router.
Description
TECHNICAL FIELD OF THE INVENTION
This invention relates generally to the field of communications, and more particularly
to self-regulating the relative priorities of packets in multiple media streams.
BACKGROUND OF THE INVENTION
Current packet-based communications systems utilize packets that make up
a media stream that passes through routers and/or switches as the media stream
traverses from its point of origin endpoint to its final destination endpoint.
Each router/switch through which the packets pass potentially introduces jitter
to the packets of the media stream. Different types of media streams are prioritized
as a function of their susceptibility to degradation based on jitter. The most
time sensitive media streams typically are the most susceptible to degradation
from jitter. For example, voice packets are typically more time sensitive than
video packets, which, in turn, are typically more time sensitive than electronic
mail packets. As a result, the priority of the packets will be marked accordingly.
Packets are given a priority by the originating endpoint. It is the originating
point that assigns the priority to the packets. There could be however a scenario
where routing or switching is done in such a way that the router knows that the
packet contains voice versus video versus email. The routers and switches receiving
these types of packets will typically be configured to give higher priority to
the voice packet over the video and the electronic mail packets while the video
packet will likely be given a higher priority than the electronic mail packet.
Thus, packets at a router awaiting transmission from the router will be scheduled
for transmission based on the priority associated with the type of each packet
awaiting transmission.
SUMMARY OF THE INVENTION
The present invention solves many of the problems and disadvantages associated
with prior communications systems. In a particular embodiment, the present invention
provides selective priority (i.e., subpriority) among packets of the same priority
for transmission of the packets from a router. For example, all voice packets have
the same priority, all video packets have the same priority and all email packets
have the same priority, but within each of these priorities, under the present
invention, subpriorities as established. Self-regulating quality of service refers
to the ability of the router to determine and assign these subpriorities to a plurality
of packets that are tagged by an originating endpoint with the same priority (e.g.
voice packets). Endpoints assign priorities to media streams. However, all voice
packets will have the same priority assigned to the packets. The present invention
seeks to reduce the jitter and delay to media streams that have voice quality affecting
delay and jitter while adding small (unnoticeable) amounts of jitter and delay
to media streams that have negligible jitter and delay.
In an aspect of the present invention, the method and system for self-regulating
quality of service in a communications network include measuring the amount of
jitter of a first media stream received in a router, comparing the amount of jitter
of the first media stream received in the router to the amount of jitter of at
least one other media stream received in the router, and prioritizing the timing
of the transmission of a packet in the first media stream from the router based
at least in part on the results of the comparison. The packet in an embodiment
is a voice packet. In other embodiments, the packet can be a video or an email,
among others. The method and system further include storing the measurement of
jitter of the first media stream containing the packet and the at least one other
media stream and in prioritizing includes optimizing quality of service. The step
of prioritizing includes timing the transmission of the packet before the transmission
of a packet from the at least one other media stream when the first media stream
has a greater amount of jitter than the at least one other media stream.
In another aspect of the invention, the method and system for self-regulating
quality of service in a communications network include receiving at a first router
a measurement of the amount of jitter associated with a third router and prioritizing
the timing of the transmission of a packet in a media stream from the first router
via a second router toward the third router based at least in part on the amount
of jitter associated with the third router. The method and system include having
the amount of jitter associated with the third router communicated to the first
router. In the method and system according to this particular embodiment, the third
router prioritizes the timing of the transmission of the packet from the first
router. This particular embodiment further includes measuring the amount of jitter
associated with the media stream at the third router and communicating the amount
of jitter associated with the media stream at the third router to the first router.
In yet another aspect of the invention, the method and system for self-regulating
quality of service in a communications network include measuring the level of jitter
introduced by each of at least one router in a communication path of the media
stream associated with a packet, informing a central server of the level of jitter
introduced by each of the at least one router, analyzing at the central server
the level of jitter introduced by each of the at least one router and providing
input from the central server to at least one router in the communication path
based at least in part on the measured amounts of jitter.
In still another aspect of the invention, the method and system for self-regulating
quality of service in a communications network include measuring the amount of
jitter of a first media stream received in a first router to be transmitted to
a second router, comparing the amount of jitter of the first media stream received
in the first router to the amount of jitter of at least one other media stream
received in the first router, receiving at the first router a measurement of the
amount of jitter added to the media stream at a third router and prioritizing the
timing of the transmission of a packet in the media stream from the first router
via the second router toward the third router based at least in part on the results
of the comparison step and at least in part on the amount of jitter added to the
media stream at the third router. In an aspect of this embodiment, the packet is
a voice packet. Other embodiments can include video packets and email packets among
others. In yet another aspect of this embodiment, the method and system include
storing the measurement of jitter of the first media stream and the at least one
other media stream and the step of prioritizing includes optimizing quality of
service. In another aspect of this embodiment, the step of prioritizing includes
timing the transmission of the packet before the transmission of a packet from
the at least one other media stream when the first media stream has a greater amount
of jitter than the at least one other media stream.
Important technical advantages of certain embodiments of the present invention
may include, among others, selective priority per connection within the routers
based on the jitter of specific media streams, providing preferential treatment
to media streams, with high jitter and preventing or at least reducing the degradation
below an acceptable level of the voice quality of voice streams. This provides
selective priority for one voice stream over another voice stream of the same identically
tagged priority.
Another important technical advantage of the present invention may include
the subpriority assigned to each media stream based on the measured jitter within
that router. A further important technical advantage of the present invention may
include the sub-priority assigned based on the end to end jitter measurement as
collected by a central server.
Yet another important technical advantage of the present invention may include
adding less delay and jitter to voice streams with high jitter and delay that,
as a result, will reduce the impact to the perceived voice quality of those voice
streams. The greater delay and jitter added to media streams with low jitter and
delay will have minimal impact to the perceived voice quality.
Other technical advantages will be readily apparent to one skilled in the art
from the following figures, descriptions, and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present invention and its advantages,
reference is now made to the following description, taken in conjunction with the
accompanying drawings, in which:
FIG. 1A illustrates one embodiment of a communication system incorporating teachings
of the present invention;
FIG. 1B is a graphical illustration of jitter as it applies to the present invention;
FIG. 2 is a flow chart illustrating an aspect of the present invention;
FIG. 3 is a flow chart illustrating an aspect of the present invention;
FIG. 4 is a flowchart illustrating another aspect of the present invention;
FIG. 5 is a flowchart illustrating another aspect of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1A illustrates a communications system
10 that includes endpoints
12a,
12b,
12c,
12d and
12e (generally referred to as endpoints
12) that establish
a communication session using a network
14. Each endpoint
12 maintains
a plurality of compression/decompression modules (not shown) that compress, decompress,
and otherwise process voice, video, data, and other information (generally referred
to as media) exchanged between two or more of the endpoints
12. Endpoints
12 may also include jitter buffers
22.
The endpoints
12 may be any combination of hardware and/or software that
provide communication services to a user. For example, the endpoint
12 may
be a telephone, a computer running telephony software, a video monitor, a camera,
or any other communication or processing hardware and/or software that supports
the communication of packets
16 of media using the network
14. The
endpoints
12 may also include unattended or automated systems, gateways,
other intermediate components, or other devices that can establish media sessions.
Although FIG. 1A illustrates five endpoints
12, the communication system
10 contemplates any number and arrangement of endpoints
12 for communicating
media. For example, the described technologies and techniques for establishing
a communication session between endpoints
12 may be adapted to establish
a conference between more than two endpoints
12.
The network
14 may be a local area network (LAN), wide area network (WAN),
global distributed network such as the Internet, intranet, extranet, or any other
form of wireless or wireline communication network. Generally, the network
14
provides for the communication of packets, cells, frames, or other portion of information
(generally referred to as packets
16) between the endpoints
12. The
network
14 may include any combination of routers, hubs, switches, and other
hardware and/or software implementing any number of communication protocols that
allow for the exchange of packets in the communication system
10. In this
application, the routers, hubs, switches and other hardware and/or software between
the endpoints are referred to generally as routers
18. The packets
16
make up a media stream
20.
In a particular embodiment, the network
14 employs communication protocols
that allow for the addressing or identification of the endpoints
12 coupled
to the network
14. For example, using Internet protocol (IP), each of the
components coupled together by the network
14 in the communications system
10 may be identified in information directed using IP addresses. In this
manner, the network
14 may support any form and combination of point-to-point,
multicast, unicast, or other techniques for exchanging media packets among components
in the system
10. Due to congestion, component failure, or other circumstance,
the network
14 may experience performance degradation in exchanging packets
16 between endpoints
12. One or more parameters reflect the performance
of the network
14. These network parameters may include delay, jitter, packet
fragmentation, packet loss, or any other measure that indicates or reflects the
performance of the network
14. In a particular embodiment, the network parameter
of jitter is assessed for each media stream
20 at each router
18
using the techniques known in the art using hardware and/or software. Jitter as
used herein is the relative time shift among packets
16 in the media stream
20.
FIG. 1B illustrates jitter as it applies to the present invention. For example,
an endpoint
12a may represent the point of origin of a media stream
20a. At the endpoint
12a, each packet
16 is
spaced 20 msec from the preceding packet
16 in the media stream
20a
as shown at the left side of FIG. 1B. The lengths of the packets
16
are not drawn to scale in FIG. 1B and would depend on the speed of the link. Through
variable delays in routers
18, the packets
16 of the media stream
20a received near a final destination endpoint
12b no
longer are equally spaced apart. This is illustrated at the right side of FIG.
1B. The arrow
20a-
1 in FIG. 1A represents the first media
stream
20a near the point or origin endpoint
12a and
the arrow
20a-
2 represents the first media stream
20a
near the point of destination endpoint
12b. Some packets
16
may be received at the endpoint
12b less than 20 msec from the preceding
packet while other packets may be received at the endpoint
12b more
than 20 msec from the preceding packet.
Typically, the packets
16 received at the final destination endpoint
12b are placed in the jitter buffer
22 which can be implemented
using hardware and/or software. In this example where the packets
16 were
spaced 20 msec apart at the origination endpoint
12a, the jitter
buffer
22 passes along each succeeding packet
20 msec from the transmission
of the preceding packet
16 thereby restoring the original timing sequence.
It is often desirable to minimize the number of packets
16 in the jitter
buffer
22 at any one time. For example, it is especially desirable with
respect to voice packets, in order to minimize the time delay between origination
and receipt of a voice communication. However, having no packets
16 in the
jitter buffer
22 during the transmission of a voice stream, results in the
degradation of the perceived voice quality. Thus, reducing the size of the jitter
buffer
22 must be balanced against ensuring that the jitter buffer does
not empty completely.
In a particular embodiment, the overall adverse effect of the jitter at all the
final destination endpoints
12, e.g., endpoints
12b and
12d,
in the network are reduced. Other embodiments include reducing the overall adverse
affects of jitter in video and other media.
FIG. 2 illustrates a flow chart of a method of the particular embodiment directed
to voice packets. The method begins at step
200 where a router
18a
receives a first voice packet
16a that is part of the first voice
stream
20a between origination endpoint
12a and final
destination endpoint
12b. At step
202, the amount of jitter
of the first voice stream
20a at the router
18a is
measured using a measuring system
24 (see FIG. 1) known in the art. Alternatively,
rather than measure jitter directly, the number of routers
18 through which
the packet
16a has traversed (i.e., the number of hops) can be used
as a guide to the amount of jitter in the packet
16a. Typically,
the more routers
18 through which the packet
16a has traversed,
the more jitter would have been added to the packet, compared to other packets
16 of the same type having traversed through fewer routers. Thus, the number
of routers can be used in lieu of direct jitter measurements. The number of hops
can be determined from the header of the packet. Unless otherwise specified, in
this disclosure reference to measuring jitter, such as by the measuring system
24, includes but is not limited to methods or systems for determining the
number of routers
18 through which the packet
16 has traversed. Similarly,
reference to measured jitter includes but is not limited to the number of routers
18 through which the packet
16 has traversed. That determined number
of routers can be the basis for determining subpriorities for packets
16
as is further discussed in detail below.
The measurement of the jitter of the first media stream
20a is
compared at step
204 to measurements in a table
26 of the jitter
of other media stream
20 in a queue
28 associated with the router
18a for packets
16 awaiting transmission from the router.
While each router
18 may be associated with its own plurality of jitter
measuring systems
24, tables
26 and/or queues
28 in these
particular embodiments, for simplicity, the measuring system, table and queue are
shown only with respect to router
18a in FIG. 1. Further note that
while the jitter measuring system
24, the table
26 and the queue
28 are shown as being external to the router
18a in FIG. 1,
any or all of these components may be integral to the router. As known to those
skilled in the art, each router
18 has many ports (not shown) and the router
would thus have many queues
28, at least one per port. For simplicity, only
one queue
28 is shown in FIG. 1. Each queue
28 typically would contain
many packets
16 from many media streams
20. The table
26 and
the queue
28 can be implemented using hardware and/or software. At step
206, the first voice packet
16a is positioned in the queue
28 at least in part based on the measurement of the jitter of the first
media stream
20a, typically being placed in the queue ahead of other
voice packets in media streams
20 with measurements of less jitter and behind
other voice packets in media streams
20 with measurements of more jitter.
Other factors may be considered by the system in determining the placement of the
first voice packet
16a, such as the amount of time one or more of
the other voice packets have been in the queue
28.
At step
208, the position of the first voice packet
16a in
the queue
28 and the measurement of the jitter of the first media stream
20a is stored in the table
26. The process then returns to
step
200, where the router
18a receives a second voice packet
16b that is part of a second media stream
20b between
the origination endpoint
12c and the final destination endpoint
12d.
The arrow
20b-
1 in FIG. 1A represents the second media stream
20b near the point of origin endpoint
12c and the arrow
20b-
2 represents the second media stream near the point of
destination endpoint
12d. At step
202, the amount of jitter
of the second media stream
20b is measured. At step
204, the
measurement of the second media stream
20b is compared to the measurements
in the table
26 of the jitter of the other media streams
20, including
the first media stream
20a whose measurement is stored with the first
voice packet
16a in the queue
28. At step
206, the
second voice packet
16b is positioned in the queue
28 at least
in part based on the measurement of the jitter of the second media stream
20b.
The position in the queue of the second voice packet
16b and the
measurement of its associated jitter is stored in the table
26 at step
208.
For example, if the amount of jitter measured with respect to the second media
stream
20b is greater than the amount of jitter measured with respect
to the first media stream
20a, the second voice packet typically
will be placed in the queue
28 ahead of the first voice packet even though
the first voice packet reached the queue first. The process then returns to step
200, as necessary.
FIG. 3 illustrates another particular embodiment of the invention. At step
300,
the amount of jitter added to a media stream
20a is measured by a
third router
18c by means known to those skilled in the art. For
example, the table
26 contains the measured amounts of jitter for each media
stream
20 in the queue
28 as measured at the third router
18c.
The amount of jitter measured at the third router
18c is communicated,
in step
302, to the first router
18a. In step
304,
the timing of the transmission of the packet
16a from the first router
18a via a second router
18b to the third router
18c
is prioritized based at least in part on the amount of jitter measured at the
third router. For example, were the amount of jitter associated with the media
stream
20 as measured by the third router
18c to be higher
than a specific threshold, the packet
16a may be moved higher in
the queue
28 at the first router
18a for earlier transmission.
The prioritization of packet transmission from the first router
18a may
include an analysis of the measured amounts of jitter associated with a number
of routers
18, in addition to the third router
18c. Accordingly,
packet transmission from the first router
18a can be scheduled so
as to reduce the amount of jitter introduced at the first router for a particular
media stream
20, in this example, the packet
16a to be transmitted
to the third router
18c via the second router
18b,
at the expense of a second packet
16b to be transmitted to a fourth
router
18d from the first router
18a via the second
router
18b based on the information that a higher amount of jitter
of the media stream
20a containing the packet
16a to
be transmitted to the third router
18c will likely be introduced
than with the second packet
16b to be transmitted to the fourth router
18d via the second router
18b. The amount of jitter
associated with each router
18 can be communicated to all other routers
18 in the system, to a subset of all other routers
18 in the system
or to one or more of the specific routers
18 through which the packet
16
is to be transmitted in its communication path between the endpoints
12.
FIG. 4 illustrates another particular embodiment in which, rather than having
the routers
18 communicate the measured amount of jitter to other routers,
the measured amount of jitter is first communicated to a central server
30
or software acting as a central server. In order to simplify FIG. 1, the connections
between the central server
30 and each router
18 are not shown. At
step
400, the amount of jitter at the router
18 is measured. At step
402, the measured amount of jitter is communicated to the central server
30. At step
404, the central server
30 analyzes the relative
measured amounts of jitter in two or more media streams measured in the plurality
of routers
18. The central server
30 prioritizes the transmission
of packets
16 at step
406 from the routers
18 so as to reduce
overall perceived jitter in the system
10, or alternatively in a subset
of the system. In other words, because the central server
30 is cognizant
of the amount of jitter that will be added at each router
18 in the system
10, the central server can reduce the amount of jitter introduced at certain
routers
18 for certain packets
16 that are more likely to yield the
detrimental audible effects of jitter at the expense of increasing the cummulative
amounts of jitter in packets
16 that are less likely to yield the noticeable
audible adverse effects of jitter. Note, this does not address adding jitter to,
e.g., video in order to reduce the jitter to voice. Rather jitter and delay are
added to voice packets with low jitter and delay in order to reduce the jitter
and delay in voice packets that have higher jitter and delay.
FIG. 5 illustrates yet another particular embodiment of the invention wherein
the transmission of the packet
16a is timed at least in part by the
analysis of the amount of jitter of the media stream
20a prior to
being received at the router
18a compared to other media streams
20 received by the router
18a and at least in part by the
analysis of the amount of jitter that is likely to be introduced at routers which
are expected to subsequently receive the packet. At step
500, the first
router
18a receives the first voice packet
16a from
the first media stream
20a. At step
502, the amount of jitter
in the first media stream
20a is measured by the jitter measurement
system
24. At step
504, the jitter measurement of the first media
stream
20a is compared to the measurement of jitter in other media
streams
20 in the queue
28. The amount of jitter added to the media
stream
20a by the third router
18c in the projected
path of the first media stream
20a is measured at step
506.
The amount of jitter added by the third router
18c to the media stream
20a is communicated at step
508 to the first router
18a.
At step
510, the amount of jitter added to the media stream
20a
by the third router
18c is assessed and compared to the measured
amount of jitter, if available, associated with other routers
18. At step
512, the first voice packet
16a is positioned in the queue
28 of the first router
18a based at least in part on the jitter
comparison of the packets
16 in the queue
28 of the first router
18 and based at least in part on the amount of jitter measured at the third
router
18c. At step
514, the position of the first voice packet
16a in the queue
28 and the measurement of the jitter of the
first media stream
20a at the first router
18a is stored
in the table
28.
Although the present invention has been described with several embodiments,
a myriad of changes, variations, alterations, transformations, and modifications
may be suggested to one skilled in the art, and it is intended that the present
invention encompass such changes, variations, alterations, transformations, and
modifications as fall within the scope of the appended claims.
*
