U.S. patent application number 16/684941 was filed with the patent office on 2021-05-20 for multicast support.
The applicant listed for this patent is NOKIA SOLUTIONS AND NETWORKS OY. Invention is credited to Hooman Bidgoli, Jayant Kotalwar.
Application Number | 20210152617 16/684941 |
Document ID | / |
Family ID | 1000004487588 |
Filed Date | 2021-05-20 |
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United States Patent
Application |
20210152617 |
Kind Code |
A1 |
Bidgoli; Hooman ; et
al. |
May 20, 2021 |
MULTICAST SUPPORT
Abstract
Various example embodiments for supporting multicast in
communication systems are presented. In at least some example
embodiments, supporting multicast in communication systems may
include supporting use of multicast domain information of a
penultimate hop router of the multicast domain by an egress leaf
router associated with the multicast domain for multicast service
signaling to a root router of the multicast domain. In at least
some example embodiments, in which the multicast domain is based on
Bit Index Explicit Replication (BIER), supporting multicast in
communication systems may include supporting use of BIER domain
information (e.g., a BIER Forwarding Router Identifier (BFR-ID) or
the like) of a PH BIER router by an egress leaf router associated
with the BIER domain for multicast service signaling to a root BIER
router of the BIER domain.
Inventors: |
Bidgoli; Hooman; (Ottawa,
CA) ; Kotalwar; Jayant; (Cupertino, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NOKIA SOLUTIONS AND NETWORKS OY |
Espoo |
|
FI |
|
|
Family ID: |
1000004487588 |
Appl. No.: |
16/684941 |
Filed: |
November 15, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 65/4076 20130101;
H04L 49/201 20130101; H04L 45/16 20130101 |
International
Class: |
H04L 29/06 20060101
H04L029/06; H04L 12/761 20060101 H04L012/761; H04L 12/931 20060101
H04L012/931 |
Claims
1-30. (canceled)
31. An apparatus, comprising: at least one processor; and at least
one memory including program code; wherein the at least one memory
and the program code are configured to, with the at least one
processor, cause the apparatus to at least: receive, by an egress
leaf router associated with a multicast domain from a penultimate
hop router of the multicast domain, an indication of an identifier
of the penultimate hop router in the multicast domain; and send, by
the egress leaf router toward the penultimate hop router, multicast
service signaling using the identifier of the penultimate hop
router in the multicast domain as an identifier of the egress leaf
router in the multicast domain.
32. The apparatus of claim 31, wherein the at least one memory and
the program code are configured to, with the at least one
processor, cause the apparatus to at least: send, by the egress
leaf router toward the penultimate hop router, a request by the
egress leaf router for the penultimate hop router to use
penultimate hop popping.
33. The apparatus of claim 32, wherein the request by the egress
leaf router for the penultimate hop router to use penultimate hop
popping includes an advertisement of implicit null functionality by
the egress leaf router.
34. The apparatus of claim 32, wherein the request by the egress
leaf router for the penultimate hop router to use penultimate hop
popping includes an invalid node identifier for the egress leaf
router in the multicast domain.
35. The apparatus of claim 31, wherein the indication of the
identifier of the penultimate hop router in the multicast domain is
received in an advertisement of the penultimate hop router of the
multicast domain.
36. The apparatus of claim 35, wherein the advertisement of the
penultimate hop router is received in multicast domain signaling
via a routing information protocol.
37. The apparatus of claim 31, wherein the multicast domain is a
Bit Index Explicit Replication (BIER) domain, wherein the
identifier of the penultimate hop router in the multicast domain
includes a BIER Forwarding Router Identifier (BFR-ID) of the
penultimate hop router of the multicast domain.
38. The apparatus of claim 31, wherein the multicast service
signaling includes at least one of Multicast Virtual Private
Network (MVPN) service signaling or Ethernet Virtual Private
Network (EVPN) service signaling.
39. A method, comprising: receiving, by an egress leaf router
associated with a multicast domain from a penultimate hop router of
the multicast domain, an indication of an identifier of the
penultimate hop router in the multicast domain; and sending, by the
egress leaf router toward the penultimate hop router, multicast
service signaling using the identifier of the penultimate hop
router in the multicast domain as an identifier of the egress leaf
router in the multicast domain.
40. An apparatus, comprising: at least one processor; and at least
one memory including program code; wherein the at least one memory
and the program code are configured to, with the at least one
processor, cause the apparatus to at least: receive, by a
penultimate hop router of a multicast domain from an egress leaf
router associated with the multicast domain, an indication of a
request by the egress leaf router for the penultimate hop router to
use penultimate hop popping; and send, by the penultimate hop
router toward the egress leaf router based on the indication of the
request by the egress leaf router for the penultimate hop router to
use penultimate hop popping, an advertisement including an
identifier of the penultimate hop router in the multicast
domain.
41. The apparatus of claim 40, wherein the indication of the
request by the egress leaf router for the penultimate hop router to
use penultimate hop popping includes an advertisement of implicit
null functionality by the egress leaf router.
42. The apparatus of claim 40, wherein the indication of the
request by the egress leaf router for the penultimate hop router to
use penultimate hop popping includes an invalid node identifier for
the egress leaf router in the multicast domain.
43. The apparatus of claim 40, wherein the indication of the
request by the egress leaf router for the penultimate hop router to
use penultimate hop popping is received in an advertisement of the
egress leaf router, wherein the advertisement of the egress leaf
router includes an information element including an invalid node
identifier for the egress leaf router in the multicast domain.
44. The apparatus of claim 43, wherein, to send the advertisement
including the identifier of the penultimate hop router in the
multicast domain, the at least one memory and the program code are
configured to, with the at least one processor, cause the apparatus
to at least: modify, by the penultimate hop router, the
advertisement of the egress leaf router to form a modified
advertisement of the egress leaf router; and forward, by the
penultimate hop router, the modified advertisement of the egress
leaf router.
45. The apparatus of claim 44, wherein, to modify the advertisement
of the egress leaf router to form the modified advertisement of the
egress leaf router, the at least one memory and the program code
are configured to, with the at least one processor, cause the
apparatus to at least: replace, by the penultimate hop router
within the information element, the invalid node identifier for the
egress leaf router in the multicast domain with the identifier of
the penultimate hop router in the multicast domain.
46. The apparatus of claim 44, wherein, to modify the advertisement
of the egress leaf router to form the modified advertisement of the
egress leaf router, the at least one memory and the program code
are configured to, with the at least one processor, cause the
apparatus to at least: remove, by the penultimate hop router, the
information element from the advertisement of the egress leaf
router.
47. The apparatus of claim 43, wherein, to send the advertisement
including the identifier of the penultimate hop router in the
multicast domain, the at least one memory and the program code are
configured to, with the at least one processor, cause the apparatus
to at least: forward, by the penultimate hop router, the
advertisement of the egress leaf router.
48. The apparatus of claim 40, wherein the at least one memory and
the program code are configured to, with the at least one
processor, cause the apparatus to at least: send, by the
penultimate hop router within the multicast domain, the
advertisement including the identifier of the penultimate hop
router in the multicast domain.
49. The apparatus of claim 40, wherein the at least one memory and
the program code are configured to, with the at least one
processor, cause the apparatus to at least: receive, by the
penultimate hop router from the egress leaf router, multicast
service signaling including the identifier of the penultimate hop
router as an identifier of the egress leaf router in the multicast
domain.
50. The apparatus of claim 40, wherein the at least one memory and
the program code are configured to, with the at least one
processor, cause the apparatus to at least: receive, by the
penultimate hop router via the multicast domain, a packet including
a multicast packet, a multicast domain header, and a multicast
domain label, wherein the multicast packet includes a multicast
payload and an upstream assigned label associated with the egress
leaf router; remove, by the penultimate hop router from the packet
to recover thereby the multicast packet, the multicast domain label
and the multicast domain header; and forward, by the penultimate
hop router toward the egress leaf router, the multicast packet.
51. The apparatus of claim 50, wherein, to forward the multicast
packet, the at least one memory and the program code are configured
to, with the at least one processor, cause the apparatus to at
least: send, by the penultimate hop router over each interface of
the penultimate hop router on which the penultimate hop router
received a route related to the multicast domain, the multicast
packet.
52. The apparatus of claim 50, wherein, to forward the multicast
packet, the at least one memory and the program code are configured
to, with the at least one processor, cause the apparatus to at
least: determine, by the penultimate hop router based on a mapping
of the upstream assigned label for the egress leaf router to a
multicast domain prefix for the egress leaf router, an interface of
the penultimate hop router that is connected to the egress leaf
router; and send, by the penultimate hop router via the interface
of the penultimate hop router that is connected to the egress leaf
router, the multicast packet.
53. The apparatus of claim 40, wherein the multicast domain is a
Bit Index Explicit Replication (BIER) domain, wherein the
identifier of the penultimate hop router in the multicast domain
includes a BIER Forwarding Router Identifier (BFR-ID) of the
penultimate hop router of the multicast domain.
54. The apparatus of claim 49, wherein the multicast service
signaling includes at least one of Multicast Virtual Private
Network (MVPN) service signaling or Ethernet Virtual Private
Network (EVPN) service signaling.
55. A method, comprising: receiving, by a penultimate hop router of
a multicast domain from an egress leaf router associated with the
multicast domain, an indication of a request by the egress leaf
router for the penultimate hop router to use penultimate hop
popping; and sending, by the penultimate hop router toward the
egress leaf router based on the indication of the request by the
egress leaf router for the penultimate hop router to use
penultimate hop popping, an advertisement including an identifier
of the penultimate hop router in the multicast domain.
Description
TECHNICAL FIELD
[0001] Various example embodiments relate generally to
communication systems, and more particularly but not exclusively,
to supporting multicast in communication systems.
BACKGROUND
[0002] Multicast is used in many types of communication networks to
deliver various types of information.
SUMMARY
[0003] In at least some example embodiments, an apparatus includes
at least one processor and at least one memory including program
code, wherein the at least one memory and the program code are
configured to, with the at least one processor, cause the apparatus
to at least send, by an egress leaf router associated with a
multicast domain toward a penultimate hop router of the multicast
domain, an indication of a request by the egress leaf router to use
multicast domain information of the penultimate hop router of the
multicast domain. In at least some example embodiments, the
multicast domain information of the penultimate hop router includes
an identifier of the penultimate hop router within the multicast
domain. In at least some example embodiments, the indication of the
request by the egress leaf router to use multicast domain
information of the penultimate hop router of the multicast domain
includes a request by the egress leaf router for the penultimate
hop router to use penultimate hop popping. In at least some example
embodiments, the indication of the request by the egress leaf
router to use multicast domain information of the penultimate hop
router of the multicast domain includes an invalid node identifier
provided by the egress leaf router. In at least some example
embodiments, the at least one memory and the program code are
configured to, with the at least one processor, cause the apparatus
to at least receive, by the egress leaf router from the penultimate
hop router, an advertisement including the multicast domain
information of the penultimate hop router of the multicast domain.
In at least some example embodiments, the at least one memory and
the program code are configured to, with the at least one
processor, cause the apparatus to at least send, by the egress leaf
router toward the penultimate hop router, multicast service
signaling including the multicast domain information of the
penultimate hop router of the multicast domain. In at least some
example embodiments, the multicast service signaling includes at
least one of Multicast Virtual Private Network (MVPN) service
signaling or Ethernet Virtual Private Network (EVPN) service
signaling. In at least some example embodiments, the multicast
domain is a Bit Index Explicit Replication (BIER) domain, wherein
the multicast domain information of the penultimate hop router of
the multicast domain includes a BIER Forwarding Router Identifier
(BFR-ID) of the penultimate hop router of the multicast domain. In
at least some example embodiments, the indication of the request by
the egress leaf router to use multicast domain information of the
penultimate hop router of the multicast domain includes an invalid
BIER Forwarding Router Identifier (BFR-ID) provided by the egress
leaf router. In at least some example embodiments, the indication
of the request by the egress leaf router to use multicast domain
information of the penultimate hop router of the multicast domain
includes an implicit null label or an implicit null
type-length-value (TLV).
[0004] In at least some example embodiments, a non-transitory
computer-readable medium includes instructions configured to cause
an apparatus to at least send, by an egress leaf router associated
with a multicast domain toward a penultimate hop router of the
multicast domain, an indication of a request by the egress leaf
router to use multicast domain information of the penultimate hop
router of the multicast domain. In at least some example
embodiments, the multicast domain information of the penultimate
hop router includes an identifier of the penultimate hop router
within the multicast domain. In at least some example embodiments,
the indication of the request by the egress leaf router to use
multicast domain information of the penultimate hop router of the
multicast domain includes a request by the egress leaf router for
the penultimate hop router to use penultimate hop popping. In at
least some example embodiments, the indication of the request by
the egress leaf router to use multicast domain information of the
penultimate hop router of the multicast domain includes an invalid
node identifier provided by the egress leaf router. In at least
some example embodiments, the non-transitory computer-readable
medium includes instructions configured to cause the apparatus to
at least receive, by the egress leaf router from the penultimate
hop router, an advertisement including the multicast domain
information of the penultimate hop router of the multicast domain.
In at least some example embodiments, the non-transitory
computer-readable medium includes instructions configured to cause
the apparatus to at least send, by the egress leaf router toward
the penultimate hop router, multicast service signaling including
the multicast domain information of the penultimate hop router of
the multicast domain. In at least some example embodiments, the
multicast service signaling includes at least one of Multicast
Virtual Private Network (MVPN) service signaling or Ethernet
Virtual Private Network (EVPN) service signaling. In at least some
example embodiments, the multicast domain is a Bit Index Explicit
Replication (BIER) domain, wherein the multicast domain information
of the penultimate hop router of the multicast domain includes a
BIER Forwarding Router Identifier (BFR-ID) of the penultimate hop
router of the multicast domain. In at least some example
embodiments, the indication of the request by the egress leaf
router to use multicast domain information of the penultimate hop
router of the multicast domain includes an invalid BIER Forwarding
Router Identifier (BFR-ID) provided by the egress leaf router. In
at least some example embodiments, the indication of the request by
the egress leaf router to use multicast domain information of the
penultimate hop router of the multicast domain includes an implicit
null label or an implicit null type-length-value (TLV).
[0005] In at least some example embodiments, a method includes
sending, by an egress leaf router associated with a multicast
domain toward a penultimate hop router of the multicast domain, an
indication of a request by the egress leaf router to use multicast
domain information of the penultimate hop router of the multicast
domain. In at least some example embodiments, the multicast domain
information of the penultimate hop router includes an identifier of
the penultimate hop router within the multicast domain. In at least
some example embodiments, the indication of the request by the
egress leaf router to use multicast domain information of the
penultimate hop router of the multicast domain includes a request
by the egress leaf router for the penultimate hop router to use
penultimate hop popping. In at least some example embodiments, the
indication of the request by the egress leaf router to use
multicast domain information of the penultimate hop router of the
multicast domain includes an invalid node identifier provided by
the egress leaf router. In at least some example embodiments, the
method includes receiving, by the egress leaf router from the
penultimate hop router, an advertisement including the multicast
domain information of the penultimate hop router of the multicast
domain. In at least some example embodiments, the method includes
sending, by the egress leaf router toward the penultimate hop
router, multicast service signaling including the multicast domain
information of the penultimate hop router of the multicast domain.
In at least some example embodiments, the multicast service
signaling includes at least one of Multicast Virtual Private
Network (MVPN) service signaling or Ethernet Virtual Private
Network (EVPN) service signaling. In at least some example
embodiments, the multicast domain is a Bit Index Explicit
Replication (BIER) domain, wherein the multicast domain information
of the penultimate hop router of the multicast domain includes a
BIER Forwarding Router Identifier (BFR-ID) of the penultimate hop
router of the multicast domain. In at least some example
embodiments, the indication of the request by the egress leaf
router to use multicast domain information of the penultimate hop
router of the multicast domain includes an invalid BIER Forwarding
Router Identifier (BFR-ID) provided by the egress leaf router. In
at least some example embodiments, the indication of the request by
the egress leaf router to use multicast domain information of the
penultimate hop router of the multicast domain includes an implicit
null label or an implicit null type-length-value (TLV).
[0006] In at least some example embodiments, an apparatus includes
means for sending, by an egress leaf router associated with a
multicast domain toward a penultimate hop router of the multicast
domain, an indication of a request by the egress leaf router to use
multicast domain information of the penultimate hop router of the
multicast domain. In at least some example embodiments, the
multicast domain information of the penultimate hop router includes
an identifier of the penultimate hop router within the multicast
domain. In at least some example embodiments, the indication of the
request by the egress leaf router to use multicast domain
information of the penultimate hop router of the multicast domain
includes a request by the egress leaf router for the penultimate
hop router to use penultimate hop popping. In at least some example
embodiments, the indication of the request by the egress leaf
router to use multicast domain information of the penultimate hop
router of the multicast domain includes an invalid node identifier
provided by the egress leaf router. In at least some example
embodiments, the apparatus includes means for receiving, by the
egress leaf router from the penultimate hop router, an
advertisement including the multicast domain information of the
penultimate hop router of the multicast domain. In at least some
example embodiments, the apparatus includes means for sending, by
the egress leaf router toward the penultimate hop router, multicast
service signaling including the multicast domain information of the
penultimate hop router of the multicast domain. In at least some
example embodiments, the multicast service signaling includes at
least one of Multicast Virtual Private Network (MVPN) service
signaling or Ethernet Virtual Private Network (EVPN) service
signaling. In at least some example embodiments, the multicast
domain is a Bit Index Explicit Replication (BIER) domain, wherein
the multicast domain information of the penultimate hop router of
the multicast domain includes a BIER Forwarding Router Identifier
(BFR-ID) of the penultimate hop router of the multicast domain. In
at least some example embodiments, the indication of the request by
the egress leaf router to use multicast domain information of the
penultimate hop router of the multicast domain includes an invalid
BIER Forwarding Router Identifier (BFR-ID) provided by the egress
leaf router. In at least some example embodiments, the indication
of the request by the egress leaf router to use multicast domain
information of the penultimate hop router of the multicast domain
includes an implicit null label or an implicit null
type-length-value (TLV). In at least some example embodiments, an
apparatus includes at least one processor and at least one memory
including program code, wherein the at least one memory and the
program code are configured to, with the at least one processor,
cause the apparatus to at least receive, by a penultimate hop
router of a multicast domain from an egress leaf router associated
with the multicast domain, an indication of a request by the egress
leaf router to use multicast domain information of the penultimate
hop router of the multicast domain. In at least some example
embodiments, the multicast domain information of the penultimate
hop router includes an identifier of the penultimate hop router
within the multicast domain. In at least some example embodiments,
the indication of the request by the egress leaf router to use
multicast domain information of the penultimate hop router of the
multicast domain includes a request by the egress leaf router for
the penultimate hop router to use penultimate hop popping. In at
least some example embodiments, the indication of the request by
the egress leaf router to use multicast domain information of the
penultimate hop router of the multicast domain includes an invalid
node identifier provided by the egress leaf router. In at least
some example embodiments, the at least one memory and the program
code are configured to, with the at least one processor, cause the
apparatus to at least send, by the penultimate hop router toward
the egress leaf router, an advertisement including the multicast
domain information of the penultimate hop router of the multicast
domain. In at least some example embodiments, the at least one
memory and the program code are configured to, with the at least
one processor, cause the apparatus to at least send, by the
penultimate hop router within the multicast domain based on the
indication of the request by the egress leaf router to use
multicast domain information of the penultimate hop router of the
multicast domain, an advertisement including the multicast domain
information of the penultimate hop router of the multicast domain.
In at least some example embodiments, the indication of the request
by the egress leaf router to use multicast domain information of
the penultimate hop router of the multicast domain includes an
invalid node identifier provided by the egress leaf router. In at
least some example embodiments, to send the advertisement including
the multicast domain information of the penultimate hop router of
the multicast domain, the at least one memory and the program code
are configured to, with the at least one processor, cause the
apparatus to at least remove, from the advertisement, the invalid
node identifier provided by the egress leaf router. In at least
some example embodiments, to send the advertisement including the
multicast domain information of the penultimate hop router of the
multicast domain, the at least one memory and the program code are
configured to, with the at least one processor, cause the apparatus
to at least maintain, within the advertisement, the invalid node
identifier provided by the egress leaf router. In at least some
example embodiments, the at least one memory and the program code
are configured to, with the at least one processor, cause the
apparatus to at least receive, by the penultimate hop router from
the egress leaf router, multicast service signaling including the
multicast domain information of the penultimate hop router of the
multicast domain. In at least some example embodiments, the
multicast service signaling includes at least one of Multicast
Virtual Private Network (MVPN) signaling or Ethernet Virtual
Private Network (EVPN) signaling. In at least some example
embodiments, the at least one memory and the program code are
configured to, with the at least one processor, cause the apparatus
to at least receive, by the penultimate hop router via the
multicast domain, a packet including a multicast packet, a
multicast domain header, and a multicast domain label, wherein the
multicast packet includes a multicast payload and an upstream
assigned label associated with the egress leaf router, remove, by
the penultimate hop router from the packet the multicast domain
label and the multicast domain header, to recover thereby the
multicast packet, and forward, by the penultimate hop router toward
the egress leaf router, the multicast packet. In at least some
example embodiments, to forward the multicast packet, the at least
one memory and the program code are configured to, with the at
least one processor, cause the apparatus to at least send, by the
penultimate hop router, the multicast packet over each interface of
the penultimate hop router on which the penultimate hop router
received a route related to the multicast domain. In at least some
example embodiments, to forward the multicast packet, the at least
one memory and the program code are configured to, with the at
least one processor, cause the apparatus to at least determine, by
the penultimate hop router, based on a mapping of the upstream
assigned label for the egress leaf router to a multicast domain
prefix for the egress leaf router, an interface of the penultimate
hop router that is connected to the egress leaf router and send, by
the penultimate hop router via the interface of the penultimate hop
router that is connected to the egress leaf router, the multicast
packet. In at least some example embodiments, the at least one
memory and the program code are configured to, with the at least
one processor, cause the apparatus to at least determine the
mapping of the upstream assigned label for the egress leaf router
to the multicast domain prefix for the egress leaf router based on
routes advertised by a routing information protocol. In at least
some example embodiments, the multicast domain is a Bit Index
Explicit Replication (BIER) domain, wherein the multicast domain
information of the penultimate hop router of the multicast domain
includes a BIER Forwarding Router Identifier (BFR-ID) of the
penultimate hop router. In at least some example embodiments, the
indication of the request by the egress leaf router to use
multicast domain information of the penultimate hop router of the
multicast domain comprises an invalid BIER Forwarding Router
Identifier (BFR-ID). In at least some example embodiments, the
indication of the request by the egress leaf router to use
multicast domain information of the penultimate hop router of the
multicast domain includes an implicit null label or an implicit
null type-length-value (TLV).
[0007] In at least some example embodiments, a non-transitory
computer-readable medium includes instructions configured to cause
an apparatus to at least receive, by a penultimate hop router of a
multicast domain from an egress leaf router associated with the
multicast domain, an indication of a request by the egress leaf
router to use multicast domain information of the penultimate hop
router of the multicast domain. In at least some example
embodiments, the multicast domain information of the penultimate
hop router includes an identifier of the penultimate hop router
within the multicast domain. In at least some example embodiments,
the indication of the request by the egress leaf router to use
multicast domain information of the penultimate hop router of the
multicast domain includes a request by the egress leaf router for
the penultimate hop router to use penultimate hop popping. In at
least some example embodiments, the indication of the request by
the egress leaf router to use multicast domain information of the
penultimate hop router of the multicast domain includes an invalid
node identifier provided by the egress leaf router. In at least
some example embodiments, the non-transitory computer-readable
medium includes instructions configured to cause the apparatus to
at least send, by the penultimate hop router toward the egress leaf
router, an advertisement including the multicast domain information
of the penultimate hop router of the multicast domain. In at least
some example embodiments, the non-transitory computer-readable
medium includes instructions configured to cause the apparatus to
at least send, by the penultimate hop router within the multicast
domain based on the indication of the request by the egress leaf
router to use multicast domain information of the penultimate hop
router of the multicast domain, an advertisement including the
multicast domain information of the penultimate hop router of the
multicast domain. In at least some example embodiments, the
indication of the request by the egress leaf router to use
multicast domain information of the penultimate hop router of the
multicast domain includes an invalid node identifier provided by
the egress leaf router. In at least some example embodiments, to
send the advertisement including the multicast domain information
of the penultimate hop router of the multicast domain, the
non-transitory computer-readable medium includes instructions
configured to cause the apparatus to at least remove, from the
advertisement, the invalid node identifier provided by the egress
leaf router. In at least some example embodiments, to send the
advertisement including the multicast domain information of the
penultimate hop router of the multicast domain, the non-transitory
computer-readable medium includes instructions configured to cause
the apparatus to at least maintain, within the advertisement, the
invalid node identifier provided by the egress leaf router. In at
least some example embodiments, the non-transitory
computer-readable medium includes instructions configured to cause
the apparatus to at least receive, by the penultimate hop router
from the egress leaf router, multicast service signaling including
the multicast domain information of the penultimate hop router of
the multicast domain. In at least some example embodiments, the
multicast service signaling includes at least one of Multicast
Virtual Private Network (MVPN) signaling or Ethernet Virtual
Private Network (EVPN) signaling. In at least some example
embodiments, the non-transitory computer-readable medium includes
instructions configured to cause the apparatus to at least receive,
by the penultimate hop router via the multicast domain, a packet
including a multicast packet, a multicast domain header, and a
multicast domain label, wherein the multicast packet includes a
multicast payload and an upstream assigned label associated with
the egress leaf router, remove, by the penultimate hop router from
the packet the multicast domain label and the multicast domain
header, to recover thereby the multicast packet, and forward, by
the penultimate hop router toward the egress leaf router, the
multicast packet. In at least some example embodiments, to forward
the multicast packet, the non-transitory computer-readable medium
includes instructions configured to cause the apparatus to at least
send, by the penultimate hop router, the multicast packet over each
interface of the penultimate hop router on which the penultimate
hop router received a route related to the multicast domain. In at
least some example embodiments, to forward the multicast packet,
the non-transitory computer-readable medium includes instructions
configured to cause the apparatus to at least determine, by the
penultimate hop router, based on a mapping of the upstream assigned
label for the egress leaf router to a multicast domain prefix for
the egress leaf router, an interface of the penultimate hop router
that is connected to the egress leaf router and send, by the
penultimate hop router via the interface of the penultimate hop
router that is connected to the egress leaf router, the multicast
packet. In at least some example embodiments, the non-transitory
computer-readable medium includes instructions configured to cause
the apparatus to at least determine the mapping of the upstream
assigned label for the egress leaf router to the multicast domain
prefix for the egress leaf router based on routes advertised by a
routing information protocol. In at least some example embodiments,
the multicast domain is a Bit Index Explicit Replication (BIER)
domain, wherein the multicast domain information of the penultimate
hop router of the multicast domain includes a BIER Forwarding
Router Identifier (BFR-ID) of the penultimate hop router. In at
least some example embodiments, the indication of the request by
the egress leaf router to use multicast domain information of the
penultimate hop router of the multicast domain comprises an invalid
BIER Forwarding Router Identifier (BFR-ID). In at least some
example embodiments, the indication of the request by the egress
leaf router to use multicast domain information of the penultimate
hop router of the multicast domain includes an implicit null label
or an implicit null type-length-value (TLV).
[0008] In at least some example embodiments, a method includes
receiving, by a penultimate hop router of a multicast domain from
an egress leaf router associated with the multicast domain, an
indication of a request by the egress leaf router to use multicast
domain information of the penultimate hop router of the multicast
domain. In at least some example embodiments, the multicast domain
information of the penultimate hop router includes an identifier of
the penultimate hop router within the multicast domain. In at least
some example embodiments, the indication of the request by the
egress leaf router to use multicast domain information of the
penultimate hop router of the multicast domain includes a request
by the egress leaf router for the penultimate hop router to use
penultimate hop popping. In at least some example embodiments, the
indication of the request by the egress leaf router to use
multicast domain information of the penultimate hop router of the
multicast domain includes an invalid node identifier provided by
the egress leaf router. In at least some example embodiments, the
method includes sending, by the penultimate hop router toward the
egress leaf router, an advertisement including the multicast domain
information of the penultimate hop router of the multicast domain.
In at least some example embodiments, the method includes sending,
by the penultimate hop router within the multicast domain based on
the indication of the request by the egress leaf router to use
multicast domain information of the penultimate hop router of the
multicast domain, an advertisement including the multicast domain
information of the penultimate hop router of the multicast domain.
In at least some example embodiments, the indication of the request
by the egress leaf router to use multicast domain information of
the penultimate hop router of the multicast domain includes an
invalid node identifier provided by the egress leaf router. In at
least some example embodiments, sending the advertisement including
the multicast domain information of the penultimate hop router of
the multicast domain includes removing, from the advertisement, the
invalid node identifier provided by the egress leaf router. In at
least some example embodiments, sending the advertisement including
the multicast domain information of the penultimate hop router of
the multicast domain includes maintaining, within the
advertisement, the invalid node identifier provided by the egress
leaf router. In at least some example embodiments, the method
includes receiving, by the penultimate hop router from the egress
leaf router, multicast service signaling including the multicast
domain information of the penultimate hop router of the multicast
domain. In at least some example embodiments, the multicast service
signaling includes at least one of Multicast Virtual Private
Network (MVPN) signaling or Ethernet Virtual Private Network (EVPN)
signaling. In at least some example embodiments, the method
includes receiving, by the penultimate hop router via the multicast
domain, a packet including a multicast packet, a multicast domain
header, and a multicast domain label, wherein the multicast packet
includes a multicast payload and an upstream assigned label
associated with the egress leaf router, removing, by the
penultimate hop router from the packet the multicast domain label
and the multicast domain header, to recover thereby the multicast
packet, and forwarding, by the penultimate hop router toward the
egress leaf router, the multicast packet. In at least some example
embodiments, forwarding the multicast packet includes sending, by
the penultimate hop router, the multicast packet over each
interface of the penultimate hop router on which the penultimate
hop router received a route related to the multicast domain. In at
least some example embodiments, forwarding the multicast packet
includes determining, by the penultimate hop router, based on a
mapping of the upstream assigned label for the egress leaf router
to a multicast domain prefix for the egress leaf router, an
interface of the penultimate hop router that is connected to the
egress leaf router and sending, by the penultimate hop router via
the interface of the penultimate hop router that is connected to
the egress leaf router, the multicast packet. In at least some
example embodiments, the method includes determining the mapping of
the upstream assigned label for the egress leaf router to the
multicast domain prefix for the egress leaf router based on routes
advertised by a routing information protocol. In at least some
example embodiments, the multicast domain is a Bit Index Explicit
Replication (BIER) domain, wherein the multicast domain information
of the penultimate hop router of the multicast domain includes a
BIER Forwarding Router Identifier (BFR-ID) of the penultimate hop
router. In at least some example embodiments, the indication of the
request by the egress leaf router to use multicast domain
information of the penultimate hop router of the multicast domain
comprises an invalid BIER Forwarding Router Identifier (BFR-ID). In
at least some example embodiments, the indication of the request by
the egress leaf router to use multicast domain information of the
penultimate hop router of the multicast domain includes an implicit
null label or an implicit null type-length-value (TLV).
[0009] In at least some example embodiments, an apparatus includes
means for receiving, by a penultimate hop router of a multicast
domain from an egress leaf router associated with the multicast
domain, an indication of a request by the egress leaf router to use
multicast domain information of the penultimate hop router of the
multicast domain. In at least some example embodiments, the
multicast domain information of the penultimate hop router includes
an identifier of the penultimate hop router within the multicast
domain. In at least some example embodiments, the indication of the
request by the egress leaf router to use multicast domain
information of the penultimate hop router of the multicast domain
includes a request by the egress leaf router for the penultimate
hop router to use penultimate hop popping. In at least some example
embodiments, the indication of the request by the egress leaf
router to use multicast domain information of the penultimate hop
router of the multicast domain includes an invalid node identifier
provided by the egress leaf router. In at least some example
embodiments, the apparatus includes means for sending, by the
penultimate hop router toward the egress leaf router, an
advertisement including the multicast domain information of the
penultimate hop router of the multicast domain. In at least some
example embodiments, the apparatus includes means for sending, by
the penultimate hop router within the multicast domain based on the
indication of the request by the egress leaf router to use
multicast domain information of the penultimate hop router of the
multicast domain, an advertisement including the multicast domain
information of the penultimate hop router of the multicast domain.
In at least some example embodiments, the indication of the request
by the egress leaf router to use multicast domain information of
the penultimate hop router of the multicast domain includes an
invalid node identifier provided by the egress leaf router. In at
least some example embodiments, the means for sending the
advertisement including the multicast domain information of the
penultimate hop router of the multicast domain includes means for
removing, from the advertisement, the invalid node identifier
provided by the egress leaf router. In at least some example
embodiments, the means for sending the advertisement including the
multicast domain information of the penultimate hop router of the
multicast domain includes means for maintaining, within the
advertisement, the invalid node identifier provided by the egress
leaf router. In at least some example embodiments, the apparatus
includes means for receiving, by the penultimate hop router from
the egress leaf router, multicast service signaling including the
multicast domain information of the penultimate hop router of the
multicast domain. In at least some example embodiments, the
multicast service signaling includes at least one of Multicast
Virtual Private Network (MVPN) signaling or Ethernet Virtual
Private Network (EVPN) signaling. In at least some example
embodiments, the apparatus includes means for receiving, by the
penultimate hop router via the multicast domain, a packet including
a multicast packet, a multicast domain header, and a multicast
domain label, wherein the multicast packet includes a multicast
payload and an upstream assigned label associated with the egress
leaf router, means for removing, by the penultimate hop router from
the packet the multicast domain label and the multicast domain
header, to recover thereby the multicast packet, and means for
forwarding, by the penultimate hop router toward the egress leaf
router, the multicast packet. In at least some example embodiments,
the means for forwarding the multicast packet includes means for
sending, by the penultimate hop router, the multicast packet over
each interface of the penultimate hop router on which the
penultimate hop router received a route related to the multicast
domain. In at least some example embodiments, the means for
forwarding the multicast packet includes means for determining, by
the penultimate hop router, based on a mapping of the upstream
assigned label for the egress leaf router to a multicast domain
prefix for the egress leaf router, an interface of the penultimate
hop router that is connected to the egress leaf router and means
for sending, by the penultimate hop router via the interface of the
penultimate hop router that is connected to the egress leaf router,
the multicast packet. In at least some example embodiments, the
apparatus includes means for determining the mapping of the
upstream assigned label for the egress leaf router to the multicast
domain prefix for the egress leaf router based on routes advertised
by a routing information protocol. In at least some example
embodiments, the multicast domain is a Bit Index Explicit
Replication (BIER) domain, wherein the multicast domain information
of the penultimate hop router of the multicast domain includes a
BIER Forwarding Router Identifier (BFR-ID) of the penultimate hop
router. In at least some example embodiments, the indication of the
request by the egress leaf router to use multicast domain
information of the penultimate hop router of the multicast domain
comprises an invalid BIER Forwarding Router Identifier (BFR-ID). In
at least some example embodiments, the indication of the request by
the egress leaf router to use multicast domain information of the
penultimate hop router of the multicast domain includes an implicit
null label or an implicit null type-length-value (TLV).
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The teachings herein can be readily understood by
considering the following detailed description in conjunction with
the accompanying drawings, in which:
[0011] FIG. 1 depicts an example embodiment of a communication
system configured to support multicasting of information from a
multicast source to a set of multicast receivers via a BIER
domain;
[0012] FIG. 2 depicts the communication system of FIG. 1, for
illustrating a request by an egress leaf router to use information
of a PH BIER router;
[0013] FIG. 3 depicts the communication system of FIG. 1, for
illustrating flooding of information of a PH BIER router from the
PH BIER router to the BIER domain and to the egress leaf router
requesting to use information of the PH BIER router;
[0014] FIG. 4 depicts the communication system of FIG. 1, for
illustrating use of information of a PH BIER router by an egress
leaf router for multicast service signaling;
[0015] FIG. 5 depicts the communication system of FIG. 1, for
illustrating multicasting of content from the multicast source to
multicast receivers based on use of PHP at the PH BIER router;
[0016] FIG. 6 depicts an example embodiment of a method for
supporting multicasting of information from a multicast source to a
set of multicast receivers via a multicast domain based on use by
an egress leaf router of multicast domain information of a
penultimate hop router of the multicast domain; and
[0017] FIG. 7 depicts an example embodiment of a computer suitable
for use in performing various functions presented herein.
[0018] To facilitate understanding, identical reference numerals
have been used herein, wherever possible, in order to designate
identical elements that are common among the various figures.
DETAILED DESCRIPTION
[0019] Various example embodiments for supporting multicast in
communication systems are presented. Various example embodiments
for supporting multicast in communication systems are presented
within the context of a communication system that is using Bit
Index Explicit Replication (BIER) and BIER penultimate hop (PH)
popping (PHP) to support multicast; however, it will be appreciated
that various example embodiments for supporting multicast in
communication systems may be used within the various other
communication systems which may use various other multicast
techniques to support multicast. In at least some example
embodiments, supporting multicast in communication systems may
include supporting use of multicast domain information of a PH
router of the multicast domain by an egress leaf router associated
with the multicast domain for multicast service signaling to a root
router of the multicast domain. In at least some example
embodiments, the egress leaf router associated with the multicast
domain may use the multicast domain identification information of
the PH router of the multicast domain (e.g., an identifier of the
PH router within the multicast domain) as its own identification
information (e.g., as opposed to using its own identifier) for
multicast service signaling to the root router of the multicast
domain. In at least some example embodiments, in which the
multicast domain is based on BIER, supporting multicast in
communication systems may include supporting use of BIER domain
information (e.g., a BIER Forwarding Router Identifier (BFR-ID) or
the like) of a PH BIER router by an egress leaf router associated
with the BIER domain for multicast service signaling to a root BIER
router of the BIER domain. It will be appreciated that at least
some such example embodiments may obviate a need for assignment of
a BFR-ID to an egress leaf router that is not part of the BIER
datapath given that the PH BIER router removes the BIER header from
packets before forwarding packets to the egress leaf router and,
further, that obviating the need to assign a unique BFR-ID to the
egress leaf router also may provide various advantages given that
the BIER header usually can support only a limited number of bits
(e.g., currently, most implementations support a 256-bit Bit String
Length (BSL) in the BIER header). It will be appreciated that these
and various other example embodiments and advantages or potential
advantages of supporting multicast in communication systems
(including within communication systems in which multicast is
supported using BIER) may be further understood by way of reference
to the various figures, which are discussed further below.
[0020] FIG. 1 depicts an example embodiment of a communication
system configured to support multicasting of information from a
multicast source to a set of multicast receivers via a BIER
domain.
[0021] The communication system 100 supports multicasting of
content from a multicast source 101 to a set of multicast receivers
199. The communication system 100 supports multicasting of content
from the multicast source 101 to the multicast receivers 199 using
multicast techniques.
[0022] For example, the multicast source 101 may be a content
server or other suitable source of content which may be multicast
to the multicast receivers 199. For example, the multicast
receivers 199 may include end devices (e.g., end user devices,
network devices, or the like) which are the consumers of the
multicast content (e.g., smartphones, tablets, laptops,
televisions, or the like), devices supporting end devices which are
the consumers of the multicast content (e.g., customer edge
routers, gateways, or the like), or the like, as well as various
combinations thereof. For example, the multicast content may
include multimedia content, video content, audio content, software
(e.g., software releases, updated, patches, or the like), or any
other types of content which may be distributed using multicast
techniques.
[0023] The communication system 100 supports multicasting of
multicast content from the multicast source 101 to the multicast
receivers 199 using a hierarchy of multicast routers based on BIER.
The hierarchy of multicast routers based on BIER supports a BIER
domain 115. The multicast routers include a root BIER router 110, a
set of penultimate hop (PH) BIER routers 120, and a set of egress
leaf routers 130. The root BIER router 110 is configured as a
Bit-Forwarding Ingress Router (BFIR) of the BIER domain 115. The PH
BIER routers 120 may be configured to perform penultimate hop
popping (PHP) for the BIER domain 115, in which case the PH BIER
routers 120 will operate as the Bit-Forwarding Egress Routers
(BFERs) of the BIER domain 115. The set of egress leaf routers 130
may include BIER capable routers and BIER incapable routers. The
root BIER router 110 and the PH BIER routers 120 are part of the
BIER domain 115 (and, optionally, although not depicted, at least a
portion of the egress leaf routers 130 also may be considered to be
part of the BIER domain 115 under certain circumstances). For
example, BIER may be supported based on RFC 8279.
[0024] The communication system 100, as indicated above, supports
multicasting of multicast content from the multicast source 101 to
the multicast receivers 199 based on use of BIER within the BIER
domain 115. BIER utilizes BIER packets to transport multicast
packets (e.g., an upstream assigned label and a multicast payload
in the form of a customer multicast packet being sent from the
multicast source 101 to the multicast receivers 199 of the
multicast group) via the BIER domain 115. BIER utilizes a BIER
packet, including a BIER header and a BIER payload that includes
the multicast packet, to transport the multicast packet via the
BIER domain 115. BIER utilizes a bit string (referred to as the
BIER BitString) in the BIER header to identify egress leaf routers
from which the multicast packets being transported in the BIER
payloads are to exit the BIER domain 115 (referred to as BFERs),
where each bit position in the bit string corresponds to a
different one of the egress leaf routers (i.e., each bit of the bit
string provides a unique BFR-ID for the egress leaf router with
which it is associated). This provides a limitation on the number
of BFERs which may be supported for the multicast domain within a
single Set Identifier (SI), since the number of bit positions which
may be supported in a single SI in the BIER header is limited. It
will be appreciated that BIER may be hardware dependent (e.g., it
is possible that not every type of hardware is capable of
supporting the BIER datapath) such that, as noted above, the egress
leaf routers 130 serving the multicast receivers 199 may include a
combination of BIER capable routers (e.g., routers capable of
supporting the BIER datapath) and BIER incapable routers (e.g.,
routers incapable of supporting the BIER datapath).
[0025] The communication system 100, as indicated above, also
supports use of BIER PHP, which has been introduced to allow BIER
incapable routers to utilize the BIER domain 115 to operate as
egress leaf routers 130 for various virtual private network (VPN)
services (e.g., Multicast Virtual Private Network (MVPN) services,
Ethernet Virtual Private Network (EVPN) services, or the like). In
BIER PHP, the PH BIER router 120 receives a BIER packet including a
BIER header and a BIER payload that includes a multicast packet
(e.g., an upstream assigned label and a multicast payload in the
form of a customer multicast packet being sent from the multicast
source 101 to the multicast receivers 199 of the multicast group),
removes the BIER header from the BIER packet to recover the
multicast packet being transported as the BIER payload (e.g., the
upstream assigned label and the multicast payload in the form of a
customer multicast packet being sent from the multicast source 101
to the multicast receivers 199 of the multicast group), and
forwards the multicast packet (e.g., the upstream assigned label
and the multicast payload in the form of a customer multicast
packet being sent from the multicast source 101 to the multicast
receivers 199 of the multicast group) recovered from the BIER
packet toward the egress leaf router(s) 130 with the upstream
assigned label as the outermost label. For example, for MVPN/EVPN
services, the upstream assigned label may be a Border Gateway
Protocol (BGP) upstream assigned label (e.g., a Multiprotocol-BGP
(MP-BGP) upstream assigned label, such as an MP-BGP upstream
assigned label that is based on the
https://tools.ietforg/html/draft-zzhang-bess-mvpn-evpn-aggregation-label--
01 document) or other suitable specific label. For example, BIER
PHP may be supported based on the https://tools.ietf
org/html/draft-zzhang-bier-php-101 document. It is noted that,
while the BIER incapable routers do not operate within the BIER
datapath (e.g., since the BIER header is removed by the PH BIER
routers), the https://tools.ietforg/html/draft-zzhang-bier-php-101
document for BIER PHP indicates that BIER signaling be started on
the BIER incapable routers such that the BIER incapable routers are
configured with BIER signaling and BFR-IDs.
[0026] The communication system 100 is configured to support use of
BIER information of a PH BIER router 120 by an egress leaf router
130 supported by the PH BIER router 120, thereby obviating a need
for the assignment of unique BIER information to the egress leaf
router 130 in addition to the PH BIER router 120. For example, the
BIER information of the PH BIER router 120 which may be used by
egress leaf router 130 may be the BFR-ID of the PH BIER router. It
will be appreciated that this may provide various advantages,
because it obviates a need for assignment of a BFR-ID to a router
that is not part of the BIER datapath (namely, the egress leaf
router 130) given that the PH BIER router 120 terminates BIER
packets by removing the BIER headers from the BIER packets before
forwarding the multicast packets (e.g., customer multicast packets
and associated upstream assigned labels) being transport in the
BIER payloads of the BIER packets to the egress leaf routers 130.
Additionally, it will be appreciated that obviating the need to
assign a unique BFR-ID to the egress leaf router 130 also may
provide various advantages given that the BFR-ID typically is a
limitation in the BIER datapath (e.g., a limitation on the number
of BFERs which may be supported in a given multicast domain within
a certain SI). In other words, use of the BFR-ID of the PH BIER
router 120 by an egress leaf router 130 supported by the PH BIER
router 120, rather than using its own unique assigned BFR-ID,
essentially enables the PH BIER router 120 to become the BFER in
place of the egress leaf router 130. As discussed further, the use
of BIER information of the PH BIER router 120 by an egress leaf
router 130 supported by the PH BIER router 120 may be used by
egress leaf routers 130 that are BIER incapable routers and/or BIER
capable routers.
[0027] The communication system 100 is configured to support
multicast in a manner configured to enable a PH BIER router 120
that is supporting an egress leaf router 130 to operate as a BFER
in place of the egress leaf router 130 while also enabling the
egress leaf router 130 to use the BFR-ID of the PH BIER router 120,
thereby obviating a need for assignment of a BFR-ID to the egress
leaf router 130 since the egress leaf router 130 is not part of the
BIER datapath given that the PH BIER router 120 supporting the
egress leaf router 130 removes the BIER headers from the BIER
packets before forwarding the multicast packets (e.g., customer
multicast packets and associated upstream assigned labels) being
transport in the BIER payloads of the BIER packets to the egress
leaf router 130. This enables the egress leaf router 130 to use the
BFR-ID of the PH BIER router 120 supporting the egress leaf router
130 in its multicast service signaling to the root BIER router 110
such that the root BIER router 110 will build the BIER header to
the PH BIER router 120 supporting the egress leaf router 130,
rather than to the egress leaf router 130, such that PHP may be
used at the PH BIER router 120. It will be appreciated that the
multicast service signaling from the egress leaf router 130 to the
root BIER router 110 may be based on a Border Gateway Protocol
(BGP), such as MP-BGP, or other suitable multicast service
signaling protocols. This provides much needed savings in the BIER
header (Bit String) given that the BFR-IDs of the leaf routers are
removed and only the BFR-IDs of the PH routers (which now are the
new EBBRs) are advertised via the MP-BGP signaling (e.g., in the
example in FIG. 1, the actual bits being used on the BIER header if
the egress leaf routers 130 advertise their own BIER-ID was 5 bits
as compared to 3 bits now that the egress leaf routers 130 use the
BFR-IDs of their connected PH BIER routers 120).
[0028] The egress leaf router 130 sends, to the PH BIER router 120,
an indication of a request by the egress leaf router 130 to use the
BFR-ID of the PH BIER router 120. The indication of the request by
the egress leaf router 130 to use the BFR-ID of the PH BIER router
120 also may be considered to be an indication of a request by the
egress leaf router 120 for the upstream BIER router to become a PH
BIER router for the egress leaf router. The indication of the
request by the egress leaf router 130 to use the BFR-ID of the PH
BIER router 120 also may be considered to be an indication of a
request by the egress leaf router 130 for the upstream BIER router,
when it becomes a PH BIER router for the egress leaf router, to
also become a BFER (e.g., having its own BFR-ID and advertising
itself to the BIER domain 115 as a BFER with its own BFR-ID) for
the egress leaf router 130. The egress leaf router 130 may send the
indication of the request by the egress leaf router 130 to use the
BFR-ID of the PH BIER router 120 by advertising implicit null
functionality to the PH BIER router 120. The egress leaf router 130
may advertise implicit null functionality to the PH BIER router 120
using an implicit null label (e.g., using a label 3 value), an
implicit null TLV (e.g., a TLV as described in the
https://tools.ietf org/html/draft-zzhang-bier-php-01 document), or
the like, as well as various combinations thereof. The egress leaf
router 130 may send the indication of the request by the egress
leaf router 130 to use the BFR-ID of the PH BIER router 120 by
advertising implicit null functionality to the PH BIER router 120
while setting the BFR-ID to an "Invalid BFR-ID" so as to indicate
to the PH BIER router 120 that the egress leaf router will use the
BFR-ID of the PH BIER router 120 and also that the egress leaf
router 130 is configured to obtain its BFR-ID from the PH BIER
router 120 automatically. It will be appreciated that other types
of indications may be used by the egress leaf router 130 to
indicate the request by the egress leaf router 130 to use the
BFR-ID of the PH BIER router 120 (e.g., a new TLV or other suitable
indicator). The advertising of implicit null functionality to the
PH BIER router 120 by the egress leaf router 130 informs the PH
BIER router 120 that it is to use PHP for popping the BIER headers
from the BIER packets before forwarding the multicast packets
(e.g., customer multicast packets and associated upstream assigned
labels) being transport in the BIER payloads of the BIER packets to
the egress leaf router 130. The PH BIER router 120 receives, from
the egress leaf router 130, the indication of the request by the
egress leaf router 130 to use the BFR-ID of the PH BIER router 120.
An example of such a process is depicted in FIG. 2.
[0029] FIG. 2 depicts the communication system of FIG. 1, for
illustrating a request by an egress leaf router 130 to use
information of a PH BIER router 120. In general, FIG. 2 illustrates
requests from each of the egress leaf routers 130 to the connected
PH BIER routers 120 requesting use of the BFR-IDs of the connected
PH BIER routers 120. More specifically, FIG. 2 illustrates that the
egress leaf router with BIER-Prefix=M sends a request to use
BFR-ID=1 of the connected PH BIER router 120, the egress leaf
routers with BIER-Prefix=N and BIER-Prefix=O send requests to use
BFR-ID=2 of the connected PH BIER router 120, and the egress leaf
routers with BIER-Prefix=P and BIER-Prefix=Q send requests to use
BFR-ID=3 of the connected PH BIER router 120.
[0030] The PH BIER router 120, based on the indication of the
request by the egress leaf router 130 to use the BFR-ID of the PH
BIER router 120, performs a number of actions. The indication of
the request by the egress leaf router 130 to use the BFR-ID of the
PH BIER router 120 causes the PH BIER router 120 to configure
itself to use PHP for popping the BIER headers from BIER packets
before forwarding the multicast packets (e.g., customer multicast
packets and associated upstream assigned labels) being transport in
the BIER payloads of the BIER packets to the egress leaf router
130. The indication of the request by the egress leaf router 130 to
use the BFR-ID of the PH BIER router 120 causes the PH BIER router
120 to configure itself to operate as a BFER for the egress leaf
router 130 (e.g., such that the PH BIER router 120 is configured to
have its own BFR-ID and to advertise itself to the BIER domain 115
as a BFER with its own BFR-ID). The indication of the request by
the egress leaf router 130 to use the BFR-ID of the PH BIER router
120 also causes the PH BIER router 120 to provide its BFR-ID to the
egress leaf router 130 for use in its multicast signaling to the
root BIER router 110.
[0031] The PH BIER router 120 may provide its BFR-ID to the BIER
domain 115 and to the egress leaf router 130 that requested to use
the BFR-ID of the PH BIER router based on flooding of its BFR-ID.
The PH BIER router 120 may flood its BFR-ID to the BIER domain 115,
including to the egress leaf router 130 that requested to use the
BFR-ID of the PH BIER router 120, using BIER signaling. The PH BIER
router 120 may flood its BFR-ID to the BIER domain 115, including
to the egress leaf router 130 that requested to use the BFR-ID of
the PH BIER router 120, using BIER signaling via a BIER sub-TLV
that includes the BFR-ID of the PH BIER router 120. The PH BIER
router 120 may flood its BFR-ID to the BIER domain 115, including
to the egress leaf router 130 that requested to use the BFR-ID of
the PH BIER router 120, using BIER signaling via a routing
information protocol (e.g., an IGP, a BGP, or the like) configured
for advertising routes. The PH BIER router 120 may flood its BFR-ID
to the BIER domain 115, including to the egress leaf router 130
that requested to use the BFR-ID of the PH BIER router 120, using
BIER signaling via a routing information protocol in various ways.
An example of such a process is depicted in FIG. 3.
[0032] FIG. 3 depicts the communication system of FIG. 1, for
illustrating flooding of information of a PH BIER router 120 from
the PH BIER router 120 to the BIER domain 115 and to the egress
leaf router 130 requesting to use information of the PH BIER router
120. In general, FIG. 3 illustrates advertisements from the PH BIER
routers 120 to the connected egress leaf routers 130 responsive to
the requests from each of the egress leaf routers 130 to the
connected PH BIER routers 120 requesting use of the BFR-IDs of the
connected PH BIER routers 120. More specifically, FIG. 3
illustrates that the PH BIER router 120 with BFR-ID=1 advertises
BFR-ID=1 to the egress leaf router with BIER-Prefix=M, the PH BIER
router 120 with BFR-ID=2 advertises BFR-ID=2 to the egress leaf
routers with BIER-Prefix=N and BIER-Prefix=O, and the PH BIER
router 120 with BFR-ID=3 advertises BFR-ID=3 to the egress leaf
routers with BIER-Prefix=P and BIER-Prefix=Q.
[0033] The PH BIER router 120 may flood its BFR-ID to the BIER
domain 115, including to the egress leaf router 130 that requested
to use the BFR-ID of the PH BIER router 120, using BIER signaling
in a manner for indicating to the BIER domain 115 that the egress
leaf router 130 has the same BFR-ID as the PH BIER router 120.
[0034] The PH BIER router 120 may flood its BFR-ID to the BIER
domain 115, including to the egress leaf router 130 that requested
to use the BFR-ID of the PH BIER router 120, using BIER signaling
without indicating to the BIER domain 115 that the egress leaf
router 130 is using the BFR-ID of the PH BIER router 120. The PH
BIER router 120 may flood its BFR-ID to the
[0035] BIER domain 115 without indicating to the BIER domain 115
that the egress leaf router 130 is using the BFR-ID of the PH BIER
router 120 by removing the BIER INFO TLV of the egress leaf router
130 (e.g., the BIER INFO TLV of the egress leaf router 130 received
by the PH BIER router 120 from the egress leaf router 130) from the
route that is advertised by the PH BIER router 120. It will be
appreciated that, in this case, the egress leaf router 130 is
removed from the BIER datapath.
[0036] The PH BIER router 120 may flood its BFR-ID to the BIER
domain 115, including to the egress leaf router 130 that requested
to use the BFR-ID of the PH BIER router 120, using BIER signaling
without indicating to the BIER domain 115 that the egress leaf
router 130 is using the BFR-ID of the PH BIER router 120. The PH
BIER router 120 may flood its BFR-ID to the BIER domain 115 without
indicating to the BIER domain 115 that the egress leaf router 130
is using the BFR-ID of the PH BIER router 120 by leaving the BFR-ID
in the BIER INFO TLV received from the egress leaf router (e.g.,
the "Invalid BFR-ID" provided in the BIER INFO TLV of the egress
leaf router) unchanged in the route that is advertised by the PH
BIER router 120.
[0037] It will be appreciated that the PH BIER router 120 may flood
its BFR-ID to the BIER domain 115, including to the egress leaf
router 130 that requested to use the BFR-ID of the PH BIER router
120, using BIER signaling via a routing information protocol in
various other ways.
[0038] The egress leaf router 130 receives the BFR-ID of the PH
BIER router 120 from the PH BIER router 120, sets the BFR-ID of the
PH BIER router 120 as its own BFR-ID, and uses the BFR-ID of the PH
BIER router 120 for multicast service signaling (e.g., MVPN, EVPN,
or the like) for establishing multicast service. The egress leaf
router 130, as indicated above, may receive the BFR-ID of the PH
BIER router 120 from the PH BIER router 120 using BIER signaling
(e.g., a BIER sub-TLV) via a routing information protocol (e.g., an
IGP, a BGP, or the like) configured for advertising routes.
[0039] The egress leaf router 130 sends multicast service
signaling, using the BFR-ID of the PH BIER router 120, toward the
root BIER router 110 for establishing multicast service. The egress
leaf router 130 sends the multicast service signaling to the
connected PH BIER router 120. The PH BIER router 120 receives the
multicast service signaling from the egress leaf router 130 and
forwards the multicast service signaling from the egress leaf
router 130 toward the root BIER router 110 such that the root BIER
router 110 learns the BFR-ID of the PH BIER router 120 from the
multicast service signaling of the egress leaf router 130. The root
BIER router 110 receives the multicast service signaling, including
the BFR-ID of the PH BIER router 120. As discussed herein, the
multicast service signaling may be based on BGP, such as MP-BGP
(e.g., based on the
https://tools.ietforg/html/draft-ietf-bier-mvpn-11 document), or
using any other suitable multicast service signaling protocol. The
multicast service signaling may include MVPN service signaling or
EVPN service signaling for establishing MVPN service or EVPN
service, respectively (or may include other suitable types of
multicast service signaling). The multicast service signaling may
be sent in various ways which may depend on the type of multicast
service signaling. For example, in the case of MVPN service
signaling or EVPN service signaling for establishing MVPN service
or EVPN service, respectively, the egress leaf router 130 may use
the BFR-ID of the PH BIER router 120 in the BFR-ID Field of the
Tunnel Attribute (PTA) of the x-PMSI (Provider Service Multicast
Interface) A-D route (e.g., as discussed in the
https://tools.ietforg/html/draft-ietf-bier-mvpn-11 document). An
example of such a process is depicted in FIG. 4.
[0040] FIG. 4 depicts the communication system of FIG. 1, for
illustrating use of information of a PH BIER router 120 (e.g., the
BFR-ID of the PH BIER router 120) by an egress leaf router 130 for
multicast service signaling. In general, FIG. 4 illustrates MVPN
service signaling from two of the egress leaf routers 130
(illustrative, the egress leaf routers 130 with BIER-Prefix IDs "N"
and "O") to their connect PH BIER router 120 (illustratively, the
PH BIER router 120 having a BFR-ID of "2") using BGP MVPN AD Route
BIER PTAs. More specifically, FIG. 4 illustrates MVPN service
signaling using BGP MVPN AD Route BIER PTAs having the following
fields: Tunnel type (=0x0B), MPLS Label, Sub-Domain, BFR-ID (=PH 2
BFR-ID=2), and BFR-Prefix. It will be appreciated that fewer or
more, as well as different, fields may be included within a BGP
MVPN AD Route BIER PTA. It will be appreciated that other route
types or data structures may be used for multicast service
signaling (e.g., for MVPN service, for other types of service such
as EVPN or the like, and so forth).
[0041] The root BIER router 110 receives the multicast service
signaling of the egress leaf router 130, learns the BFR-ID of the
PH BIER router 120 from the multicast service signaling of the
egress leaf router 130, and uses the BFR-ID of the PH BIER router
120 for building the BIER packets that are used to transport
multicast packets (including the multicast payloads of the
multicast source 101 and associated upstream assigned labels) to
the egress leaf router 130 for delivery to multicast receivers 199.
The root BIER router 110 uses the BFR-ID of the PH BIER router 120
for building the BIER packets, that are used to transport multicast
packets (including the multicast payloads of the multicast source
101 and associated upstream assigned labels) to the egress leaf
router 130 for delivery to multicast receivers 199, by building the
BIER header for the BIER packets to the PH BIER router 120 rather
than to the egress leaf router 130 that initiated the multicast
service signaling (since the BFR-ID of the PH BIER router 120,
rather than a unique BFR-ID of the egress leaf router 130, is
included in the multicast service signaling from the egress leaf
router 130). The root BIER router 110 uses the BFR-ID of the PH
BIER router 120, for building the BIER packets that are used to
transport multicast packets (including the multicast payloads of
the multicast source 101 and associated upstream assigned labels)
to the egress leaf router 130 for delivery to multicast receivers
199, by using the BFR-ID of the PH BIER router 120 to mark the
appropriate bit in the BIER-Index of the BIER headers of BIER
packets that are used to transport multicast packets (including the
multicast payloads of the multicast source 101 and associated
upstream assigned labels) to the egress leaf router 130 for
delivery to multicast receivers 199 (namely, to mark the bit in the
BIER-Index such that it identifies the PH BIER router 120 as the
BFER for the BIER packets).
[0042] The root BIER router 110 sends the BIER packets, which are
used to transport multicast packets (including the multicast
payloads of the multicast source 101 and associated upstream
assigned labels) to the egress leaf router 130 for delivery to
multicast receivers 199, via the BIER domain 115. The BIER packets
are routed through the BIER domain 115 based on the BIER header of
the BIER packets until reaching the PH BIER router 120 associated
with the egress leaf router 130. The PH BIER router 120 removes the
BIER headers from the BIER packets based on PHP (since the BIER
headers of the BIER packets are marked with the BFR-ID of the PH
BIER router 120) to recover the multicast packets from the BIER
payloads of the BIER packets and forwards the multicast packets
(including the multicast payloads of the multicast source 101 and
associated upstream assigned labels) such that the multicast
packets reach the egress leaf router 130 and, thus, such that the
multicast receivers 199 of the multicast group connected to the
egress leaf router 130 receive the multicast payloads of the
multicast packets (i.e., the original multicast payloads of the
multicast source 101). The PH BIER router 120 may forward the
multicast packets recovered from the BIER packets, such that the
multicast packets reach the egress leaf router 130, in a number of
ways as discussed further below. The egress leaf router 130
receives the multicast packets (including the multicast payloads of
the multicast source 101 and associated upstream assigned labels)
from the PH BIER router 120, removes the upstream assigned labels
from the multicast packets to recover the multicast payloads, and
forwards the multicast payloads (i.e., the original payload of the
multicast source, which may be customer multicast packets) toward
associated multicast receivers 199 supported by the egress leaf
router 130 based on the upstream assigned labels of the multicast
packets. An example of such a process is depicted in FIG. 5.
[0043] The PH BIER router 120, as indicated above, may forward the
multicast packets, such that the multicast packets reach the egress
leaf router 130, in a number of ways. However, it is noted that,
since the PH BIER router 120 is not part of the BGP signaling, the
PH BIER router 120 will not have an understanding of the upstream
assigned label of the egress leaf router 130, which may impact the
manner in which the PH BIER router determines forwarding of
multicast packets toward the egress leaf router 130. For example,
the PH BIER router 120 with BFR-ID=B does not know which upstream
assigned label was assigned to the egress leaf router 130 with
BIER-Prefix=N and which upstream assigned label was assigned to the
egress leaf router 130 with BIER-Prefix=O and, similarly, the PH
BIER router 120 with BFR-ID=C does not know which upstream assigned
label was assigned to the egress leaf router 130 with BIER-Prefix=P
and which upstream assigned label was assigned to the egress leaf
router 130 with BIER-Prefix=Q. As a result, the PH BIER router 120
may perform forwarding of the multicast packets recovered from the
BIER packets, such that the multicast recovered from the BIER
packets reach the egress leaf router 130, in a number of ways.
[0044] In at least some example embodiments, in which the PH BIER
router 120 does not attempt to learn upstream assigned label
information for the egress leaf router 130, the PH BIER router 120
will broadcast the multicast packets on all interfaces on which the
PH BIER router 120 received a route with the BIER TLV. This may
cause the multicast packets to be sent to other egress leaf
routers, in addition to the egress leaf router 130 for which the
multicast packets are intended, however, the other egress leaf
routers that do not need the multicast packets but which receive
the multicast packets anyway may simply drop the multicast packets
(e.g., based on a determination that the upstream assigned label
attached to the multicast payload in the multicast packets does not
match its own upstream assigned label).
[0045] In at least some example embodiments, in which the PH BIER
router 120 does attempt to learn upstream assigned label
information for the egress router 130, the PH BIER router 120 will
determine, based on the learned information, the interface to which
the egress leaf router 130 is connected and send the multicast
packets on the interface to which the egress leaf router 130 is
connected. The upstream assigned label information that is learned
for the egress leaf router 130 may include a mapping of the
upstream assigned label for the egress leaf router 130 to a BIER
prefix for the egress leaf router 130. The PH BIER router 120 may
learn the upstream assigned label information for the egress leaf
router 130 by listening to the routes advertised by the routing
information protocol (e.g., BGP routes of BGP) and, upon receiving
a route for the egress leaf router 130 (or any other egress leaf
router for which it is operating as a PH BIER router), noting the
upstream assigned label for the egress leaf router 130 and the
associated BIER prefix for the egress leaf router 130 such that the
PH BIER router 120 may create and store the mapping of the upstream
assigned label for the egress leaf router 130 to a BIER prefix for
the egress leaf router 130. For example, in the case of BGP, the PH
BIER router 120 can be part of the BGP domain and listen to all BGP
routes and, upon receiving a BGP AD route for the egress leaf
router 130 for which it is acting as a PH router for, noting the
upstream assigned unique label for the egress leaf router 130 and
the BIER prefix for the egress leaf router 130 such that the PH
BIER router 130 may now use the BIER prefix of the BGP AD route PTA
to determine the interface of the PH BIER router 120 via which the
PH BIER router 120 is connected to the egress leaf router 130 and
then configure the datapath to forward the multicast packets with
that specific upstream assigned label out of that interface.
[0046] It will be appreciated that, although primarily described
with respect to sending of the BIER packets which are used to
transport multicast payloads of the multicast source 101 to a
single egress leaf router 130 of a single PH BIER router 120, the
BIER packets which are used to transport multicast payloads of the
multicast source 101 may be sent to any suitable number of egress
leaf routers 130 of any suitable number of PH BIER routers 120
depending on the set of multicast receivers 199 that belong to the
associated multicast group.
[0047] FIG. 5 depicts the communication system of FIG. 1, for
illustrating multicasting of content from the multicast source 101
to multicast receivers 199 based on use of PHP at the PH BIER
routers 120. As depicted in FIG. 5, a multicast payload from the
multicast source 101 is multicasted to the multicast receivers 199
that are part of the multicast group. The multicast source 101
provides the multicast payload to the root BIER router 110 (e.g.,
where the multicast payload may be a customer multicast packet that
is configured to transport content from the multicast source 101 to
the multicast receivers 199 that are part of the multicast group,
such as an IP packet, an MPLS packet, or the like). The root BIER
router 110 receives the multicast payload from the multicast source
101, adds the upstream assigned label to the multicast payload to
form a multicast packet, and generates a BIER packet including the
multicast packet (including the multicast payload and the upstream
assigned label), based on addition of a BIER header and a BIER
label, for supporting multicasting of the multicast packet (again,
including the multicast payload and the upstream assigned label) to
each of the PH BIER routers 120 supporting egress leaf routers 130
that are serving multicast receivers 199 that are part of the
multicast group. The PH BIER routers 120 that receive the BIER
packet including the multicast packet (again, including the
multicast payload and the upstream assigned label) remove the BIER
label and the BIER header and forward the multicast packet (again,
including the multicast payload and the upstream assigned label)to
egress leaf routers 130 that are serving multicast receivers 199
that are part of the multicast group (e.g., by sending the
multicast packet over each interface of the PH BIER router 120 on
which the PH BIER router 120 received a route with the BIER TLV, by
sending the multicast packet over each interface of the PH BIER
router 120 that is determined by the PH BIER router 120 from a
mapping of the upstream assigned label for the respective egress
leaf router 130 that is included within the multicast packet to a
BIER prefix for the respective egress leaf router 130, or the
like). The egress routers 130 that receive the multicast packet
(again, including the multicast payload and the upstream assigned
label) remove the upstream assigned label from the multicast packet
to recover the multicast payload and use the upstream assigned
label to forward the recovered multicast payload to connected
multicast receivers 199 that are part of the multicast group.
[0048] It will be appreciated that, in at least some embodiments,
if an egress leaf router 130 does not advertise implicit null
functionality or is not configured to obtain its BFR-ID
automatically, the egress leaf router 130 may not use the BFR-ID of
the PH BIER router 120 and, thus, may utilize its own BFR-ID rather
than using the BFR-ID of the PH BIER router 120.
[0049] It will be appreciated that, although primarily presented
herein with respect to various example embodiments in which
multicast is based on BIER, various example embodiments presented
herein also may be used or adapted for use in networks in which
multicast is based on various other types of multicast
mechanisms.
[0050] FIG. 6 depicts an example embodiment of a method for
supporting multicasting of information from a multicast source to a
set of multicast receivers via a multicast domain based on use by
an egress leaf router of multicast domain information of a
penultimate hop router of the multicast domain. It will be
appreciated that, although primarily presented as being performed
serially, at least a portion of the functions of method 600 may be
performed contemporaneously or in a different order than as
presented with respect to FIG. 6. At block 601, method 600 begins.
At block 610, an egress leaf router associated with the multicast
domain sends, toward a penultimate hop router of the multicast
domain, an indication of a request by the egress leaf router to use
multicast domain information of the penultimate hop router of the
multicast domain. At block 620, the penultimate hop router of the
multicast domain receives, from the egress leaf router associated
with the multicast domain, the indication of the request by the
egress leaf router to use multicast domain information of the
penultimate hop router of the multicast domain. At block 699,
method 600 ends. It will be appreciated that various multicast
support functions presented herein with respect to FIGS. 1-5 may be
incorporated within the context of method 600 of FIG. 6.
[0051] Various example embodiments for supporting multicast in a
communication system may provide various advantages or potential
advantages. For example, various example embodiments for supporting
multicast may support movement of the BFER role to routers higher
in the BIER hierarchy (e.g., closer to the root BIER router),
thereby increasing the number of egress leaf routers which may be
supported given a finite number of BFR-IDs available for use within
a BIER domain and an SI. For example, various example embodiments
for supporting multicast may obviate a need for assignment of
BFR-IDs to routers that are not part of the BIER datapath (namely,
egress leaf routers) given that the PH BIER routers remove the BIER
header from packets before forwarding the packets to the egress
leaf routers. For example, various example embodiments for
supporting multicast, by obviating the need to assign unique
BFR-IDs to egress leaf routers, also may provide various advantages
given that the BFR-ID typically is a limitation in the BIER
datapath, e.g., a limitation on the number of BFERs which may be
supported in a given multicast domain and an SI (e.g., most vendors
support only a certain BSI BIER set index within a SI (e.g., 256)),
such as by providing savings to the number of bits that are used in
the BSI within a given SI by setting the PH router BFR-ID in the
BIER header and omitting the egress leaf router BFR-ID from the
BIER header (since they are replaced by the PH router). For
example, various example embodiments for supporting multicast may
support use of the BFR-IDs of PF routers by BIER capable egress
leaf routers, in addition to BIER incapable egress leaf routers,
for supporting additional savings in the BIER BIT Index space and
BFR-IDs based on use of PHP procedures. For example, various
example embodiments for supporting multicast may enable a
significantly larger number of egress leaf nodes to be supported
without requiring use of BIER packet duplication with SIs. For
example, if BIER supports only 256 bits in the BIER header, the
BIER domain would otherwise be limited to use of only 256 leaf PE
routers; however, by operating upstream PH BIER routers as BFERs
and having the egress leaf routers utilize the BFR-IDs of the PH
BIER routers, significantly more than 256 leaf PE routers may be
supported even though BIER may only support 256 bits in the BIER
header. Various example embodiments for supporting multicast in a
communication system may provide various other advantages or
potential advantages.
[0052] FIG. 7 depicts an example embodiment of a computer suitable
for use in performing various functions presented herein
[0053] .
[0054] The computer 700 includes a processor 702 (e.g., a central
processing unit, a processor, a processor having a set of processor
cores, a processor core of a processor, or the like) and a memory
704 (e.g., a random access memory, a read only memory, or the
like). The processor 702 and the memory 704 may be communicatively
connected. In at least some embodiments, the computer 700 may
include at least one processor and at least one memory including
computer program code, wherein the at least one memory and the
computer program code are configured to, with the at least one
processor, cause the computer to perform various functions
presented herein.
[0055] The computer 700 also may include a cooperating element 705.
The cooperating element 705 may be a hardware device. The
cooperating element 705 may be a process that can be loaded into
the memory 704 and executed by the processor 702 to implement
various functions presented herein (in which case, for example, the
cooperating element 705 (including associated data structures) can
be stored on a non-transitory computer-readable storage medium,
such as a storage device or other suitable type of storage element
(e.g., a magnetic drive, an optical drive, or the like)).
[0056] The computer 700 also may include one or more input/output
devices 706. The input/output devices 706 may include one or more
of a user input device (e.g., a keyboard, a keypad, a mouse, a
microphone, a camera, or the like), a user output device (e.g., a
display, a speaker, or the like), one or more network communication
devices or elements (e.g., an input port, an output port, a
receiver, a transmitter, a transceiver, or the like), one or more
storage devices (e.g., a tape drive, a floppy drive, a hard disk
drive, a compact disk drive, or the like), or the like, as well as
various combinations thereof.
[0057] It will be appreciated that computer 700 may represent a
general architecture and functionality suitable for implementing
functional elements described herein, portions of functional
elements described herein, or the like, as well as various
combinations thereof. For example, computer 700 may provide a
general architecture and functionality that is suitable for
implementing one or more elements presented herein, such as a
multicast source 101 or a portion thereof, a root BIER router 110
or a portion thereof, an element of BIER domain 115 or a portion
thereof, a PH BIER router 120 or a portion thereof, an egress leaf
router 130 or a portion thereof, a multicast receiver 199 or a
portion thereof, or the like, as well as various combinations
thereof.
[0058] It will be appreciated that at least some of the functions
presented herein may be implemented in software (e.g., via
implementation of software on one or more processors, for executing
on a general purpose computer (e.g., via execution by one or more
processors) so as to provide a special purpose computer, and the
like) and/or may be implemented in hardware (e.g., using a general
purpose computer, one or more application specific integrated
circuits, and/or any other hardware equivalents).
[0059] It will be appreciated that at least some of the functions
presented herein may be implemented within hardware, for example,
as circuitry that cooperates with the processor to perform various
functions. Portions of the functions/elements described herein may
be implemented as a computer program product wherein computer
instructions, when processed by a computer, adapt the operation of
the computer such that the methods and/or techniques described
herein are invoked or otherwise provided. Instructions for invoking
the various methods may be stored in fixed or removable media
(e.g., non-transitory computer-readable media), transmitted via a
data stream in a broadcast or other signal bearing medium, and/or
stored within a memory within a computing device operating
according to the instructions.
[0060] It will be appreciated that the term "or" as used herein
refers to a non-exclusive "or" unless otherwise indicated (e.g.,
use of "or else" or "or in the alternative").
[0061] It will be appreciated that, although various embodiments
which incorporate the teachings presented herein have been shown
and described in detail herein, those skilled in the art can
readily devise many other varied embodiments that still incorporate
these teachings.
* * * * *
References