draft-ietf-ccamp-rsvp-te-bandwidth-availability-14.txt   draft-ietf-ccamp-rsvp-te-bandwidth-availability-15.txt 
Network Working Group H. Long, M. Ye Network Working Group H. Long, M. Ye
Internet Draft Huawei Technologies Co., Ltd Internet Draft Huawei Technologies Co., Ltd
Intended status: Standards Track G. Mirsky Intended status: Standards Track G. Mirsky
ZTE ZTE
A.D'Alessandro A.D'Alessandro
Telecom Italia S.p.A Telecom Italia S.p.A
H. Shah H. Shah
Ciena Ciena
Expires: September 2019 March 6, 2019 Expires: October 2019 April 30, 2019
Ethernet Traffic Parameters with Availability Information Ethernet Traffic Parameters with Availability Information
draft-ietf-ccamp-rsvp-te-bandwidth-availability-14.txt draft-ietf-ccamp-rsvp-te-bandwidth-availability-15.txt
Abstract Abstract
A packet switching network may contain links with variable A packet switching network may contain links with variable
bandwidth, e.g., copper, radio, etc. The bandwidth of such links is bandwidth, e.g., copper, radio, etc. The bandwidth of such links is
sensitive to external environment (e.g., climate). Availability is sensitive to external environment (e.g., climate). Availability is
typically used for describing these links when doing network typically used for describing these links when doing network
planning. This document introduces an optional Availability TLV in planning. This document introduces an optional Bandwidth
Resource ReSerVation Protocol - Traffic Engineer (RSVP-TE) Availability TLV in Resource ReSerVation Protocol - Traffic Engineer
signaling. This extension can be used to set up a Generalized Multi- (RSVP-TE) signaling. This extension can be used to set up a
Protocol Label Switching (GMPLS) Label Switched Path (LSP) in Generalized Multi-Protocol Label Switching (GMPLS) Label Switched
conjunction with the Ethernet SENDER_TSPEC object. Path (LSP) in conjunction with the Ethernet SENDER_TSPEC object.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
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Internet-Drafts are draft documents valid for a maximum of six Internet-Drafts are draft documents valid for a maximum of six
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The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
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This Internet-Draft will expire on September 6, 2019. This Internet-Draft will expire on October 30, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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respect to this document. Code Components extracted from this respect to this document. Code Components extracted from this
document must include Simplified BSD License text as described in document must include Simplified BSD License text as described in
Section 4.e of the Trust Legal Provisions and are provided without Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the Simplified BSD License. warranty as described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction ................................................ 3 1. Introduction ................................................ 3
2. Overview .................................................... 4 2. Overview .................................................... 4
3. Extension to RSVP-TE Signaling............................... 5 3. Extension to RSVP-TE Signaling............................... 5
3.1. Availability TLV........................................ 5 3.1. Bandwidth Availability TLV.............................. 5
3.2. Signaling Process....................................... 6 3.2. Signaling Process....................................... 6
4. Security Considerations...................................... 7 4. Security Considerations...................................... 7
5. IANA Considerations ......................................... 7 5. IANA Considerations ......................................... 7
5.1 Ethernet Sender TSpec TLVs ............................. 7 5.1 Ethernet Sender TSpec TLVs ............................. 7
6. References .................................................. 8 6. References .................................................. 8
6.1. Normative References.................................... 8 6.1. Normative References.................................... 8
6.2. Informative References.................................. 8 6.2. Informative References.................................. 9
7. Appendix: Bandwidth Availability Example..................... 9 7. Appendix: Bandwidth Availability Example..................... 9
8. Acknowledgments ............................................ 10 8. Acknowledgments ............................................ 11
Conventions used in this document Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
The following acronyms are used in this draft: The following acronyms are used in this draft:
skipping to change at page 3, line 38 skipping to change at page 3, line 38
reservation. The bandwidth availability information should be reservation. The bandwidth availability information should be
inherited from the bandwidth availability requirements of the inherited from the bandwidth availability requirements of the
services expected to be carried on the LSP. For example, voice services expected to be carried on the LSP. For example, voice
service usually needs "five nines" bandwidth availability, while service usually needs "five nines" bandwidth availability, while
non-real time services may adequately perform at four or three nines non-real time services may adequately perform at four or three nines
bandwidth availability. Since different service types may need bandwidth availability. Since different service types may need
different availabilities guarantees, multiple <availability, different availabilities guarantees, multiple <availability,
bandwidth> pairs may be required when signaling. bandwidth> pairs may be required when signaling.
If the bandwidth availability requirement is not specified in the If the bandwidth availability requirement is not specified in the
signaling message, the bandwidth will be reserved as the highest signaling message, the bandwidth will likely be reserved as the
bandwidth availability. Suppose, for example, the bandwidth with highest bandwidth availability. Suppose, for example, the bandwidth
99.999% availability of a link is 100 Mbps; the bandwidth with with 99.999% availability of a link is 100 Mbps; the bandwidth with
99.99% availability is 200 Mbps. When a video application requests 99.99% availability is 200 Mbps. When a video application makes a
for 120 Mbps without bandwidth availability requirement, the system request for 120 Mbps without bandwidth availability requirement, the
will consider the request as 120 Mbps with 99.999% bandwidth system will consider the request as 120 Mbps with 99.999% bandwidth
availability, while the available bandwidth with 99.999% bandwidth availability, while the available bandwidth with 99.999% bandwidth
availability is only 100 Mbps, therefore the LSP path cannot be set availability is only 100 Mbps, therefore the LSP path cannot be set
up. But, in fact, the video application doesn't need 99.999% up. But, in fact, the video application doesn't need 99.999%
bandwidth availability; 99.99% bandwidth availability is enough. In bandwidth availability; 99.99% bandwidth availability is enough. In
this case, the LSP could be set up if bandwidth availability is also this case, the LSP could be set up if bandwidth availability is also
specified in the signaling message. specified in the signaling message.
To fulfill LSP setup by signaling in these scenarios, this document To fulfill LSP setup by signaling in these scenarios, this document
specifies an Availability TLV. The Availability TLV can be specifies a Bandwidth Availability TLV. The Bandwidth Availability
applicable to any kind of physical links with variable discrete TLV can be applicable to any kind of physical links with variable
bandwidth, such as microwave or DSL. Multiple Availability TLVs discrete bandwidth, such as microwave or DSL. Multiple Bandwidth
together with multiple Ethernet Bandwidth Profiles can be carried by Availability TLVs together with multiple Ethernet Bandwidth Profiles
the Ethernet SENDER_TSPEC object [RFC6003]. Since the Ethernet can be carried by the Ethernet SENDER_TSPEC object [RFC6003]. Since
FLOWSPEC object has the same format as the Ethernet SENDER_TSPEC the Ethernet FLOWSPEC object has the same format as the Ethernet
object [RFC6003], the Availability TLV can also be carried by the SENDER_TSPEC object [RFC6003], the Bandwidth Availability TLV can
Ethernet FLOWSPEC object. also be carried by the Ethernet FLOWSPEC object.
2. Overview 2. Overview
A tunnel in a packet switching network may span one or more links in A tunnel in a packet switching network may span one or more links in
a network. To setup a Label Switched Path (LSP), a node may collect a network. To setup a Label Switched Path (LSP), a node may collect
link information which is advertised in a routing message, e.g., link information which is advertised in a routing message, e.g.,
OSPF TE LSA message, by network nodes to obtain network topology OSPF TE LSA message, by network nodes to obtain network topology
information, and then calculate an LSP route based on the network information, and then calculate an LSP route based on the network
topology. The calculated LSP route is signaled using a PATH/RESV topology. The calculated LSP route is signaled using a PATH/RESV
message for setting up the LSP. message for setting up the LSP.
skipping to change at page 5, line 7 skipping to change at page 5, line 7
When a node initiates a PATH/RESV signaling to set up an LSP, the When a node initiates a PATH/RESV signaling to set up an LSP, the
PATH message should carry the <bandwidth, availability> requirement PATH message should carry the <bandwidth, availability> requirement
list as a bandwidth request. Intermediate node(s) will allocate the list as a bandwidth request. Intermediate node(s) will allocate the
bandwidth resource for each availability requirement from the bandwidth resource for each availability requirement from the
remaining bandwidth with corresponding availability. An error remaining bandwidth with corresponding availability. An error
message may be returned if any <bandwidth, availability> request message may be returned if any <bandwidth, availability> request
cannot be satisfied. cannot be satisfied.
3. Extension to RSVP-TE Signaling 3. Extension to RSVP-TE Signaling
3.1. Availability TLV 3.1. Bandwidth Availability TLV
An Availability TLV is defined as a TLV of the Ethernet SENDER_TSPEC A Bandwidth Availability TLV is defined as a TLV of the Ethernet
object [RFC6003] in this document. The Ethernet SENDER_TSPEC object SENDER_TSPEC object [RFC6003] in this document. The Ethernet
MAY include more than one Availability TLV. The Availability TLV has SENDER_TSPEC object MAY include more than one Bandwidth Availability
the following format: TLV. The Bandwidth Availability TLV has the following format:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Index | Reserved | | Index | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Availability | | Availability |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Availability TLV Figure 1: Bandwidth Availability TLV
Type (2 octets): 0x04 Type (2 octets): 0x04(suggested; TBD by IANA)
Length (2 octets): 0x0C. Indicates the length in bytes of the Length (2 octets): 0x0C. Indicates the length in bytes of the
whole TLV including the Type and Length fields, in this case 12 whole TLV including the Type and Length fields, in this case 12
bytes. bytes.
Index (1 octet): Index (1 octet):
When the Availability TLV is included, it MUST be present along When the Bandwidth Availability TLV is included, the Ethernet
with the Ethernet Bandwidth Profile TLV. If the bandwidth Bandwidth Profile TLV MUST also be included. If there are multiple
requirements in the multiple Ethernet Bandwidth Profile TLVs have bandwidth requirements present (in multiple Ethernet Bandwidth
different Availability requirements, multiple Availability TLVs Profile TLVs) and they have different availability requirements,
SHOULD be carried. In such a case, the Availability TLV has a one multiple Bandwidth Availability TLVs MUST be carried. In such a
to one correspondence with the Ethernet Bandwidth Profile TLV by case, the Bandwidth Availability TLV has a one to one
having the same value of Index field. If all the bandwidth correspondence with the Ethernet Bandwidth Profile TLV by having
requirements in the Ethernet Bandwidth Profile have the same the same value of Index field. If all the bandwidth requirements
Availability requirement, one Availability TLV SHOULD be carried. in the Ethernet Bandwidth Profile have the same Availability
In this case, the Index field is set to 0. requirement, one Bandwidth Availability TLV SHOULD be carried. In
this case, the Index field is set to 0.
Reserved (3 octets): These bits SHOULD be set to zero when sent Reserved (3 octets): These bits SHOULD be set to zero when sent
and MUST be ignored when received. and MUST be ignored when received.
Availability (4 octets): a 32-bit floating point number describes Availability (4 octets): a 32-bit floating-point number [IEEE754]
the decimal value of availability requirement for this bandwidth describes the decimal value of the availability requirement for
request. The value MUST be less than 1and is usually expressed in this bandwidth request. The value MUST be less than 1 and is
the value of 0.99/0.999/0.9999/0.99999. usually expressed in the value of 0.99/0.999/0.9999/0.99999. The
IEEE floating-point number is used here to align with [RFC8330].
However when representing values higher than 0.999999, the
floating-point number starts to introduce errors in relation to
intended precision. However in reality, 0.99999 is normally
considered as the highest availability value (5 minutes outage in
a year) in telecom network, therefore the use of floating-point
number in availability is acceptable.
3.2. Signaling Process 3.2. Signaling Process
The source node initiates a PATH message which may carry a number of The source node initiates a PATH message which may carry a number of
bandwidth requests, including one or more Ethernet Bandwidth Profile bandwidth requests, including one or more Ethernet Bandwidth Profile
TLVs and one or more Availability TLVs. Each Ethernet Bandwidth TLVs and one or more Bandwidth Availability TLVs. Each Ethernet
Profile TLV corresponds to an availability parameter in the Bandwidth Profile TLV corresponds to an availability parameter in
associated Availability TLV. the associated Bandwidth Availability TLV.
The intermediate and destination nodes check whether they can The intermediate and destination nodes check whether they can
satisfy the bandwidth requirements by comparing each bandwidth satisfy the bandwidth requirements by comparing each bandwidth
request inside the SENDER_TSPEC objects with the remaining link sub- request inside the SENDER_TSPEC objects with the remaining link sub-
bandwidth resource with respective availability guarantee on the bandwidth resource with respective availability guarantee on the
local link when the PATH message is received. local link when the PATH message is received.
o When all <bandwidth, availability> requirement requests can o When all <bandwidth, availability> requirement requests can
be satisfied (the requested bandwidth under each availability be satisfied (the requested bandwidth under each availability
parameter is smaller than or equal to the remaining bandwidth parameter is smaller than or equal to the remaining bandwidth
under the corresponding availability parameter on its local under the corresponding availability parameter on its local
link), the node SHOULD reserve the bandwidth resource from each link), the node SHOULD reserve the bandwidth resource from each
remaining sub-bandwidth portion on its local link to set up remaining sub-bandwidth portion on its local link to set up
this LSP. Optionally, a higher availability bandwidth can be this LSP. Optionally, a higher availability bandwidth can be
allocated to lower availability request when the lower allocated to a lower availability request when the lower
availability bandwidth cannot satisfy the request. availability bandwidth cannot satisfy the request.
o When at least one <bandwidth, availability> requirement o When at least one <bandwidth, availability> requirement
request cannot be satisfied, the node SHOULD generate PathErr request cannot be satisfied, the node SHOULD generate PathErr
message with the error code "Admission Control Error" and the message with the error code "Admission Control Error" and the
error value "Requested Bandwidth Unavailable" (see [RFC2205]). error value "Requested Bandwidth Unavailable" (see [RFC2205]).
When two LSPs request bandwidth with the same availability When two LSPs request bandwidth with the same availability
requirement, contention MUST be resolved by comparing the node IDs, requirement, contention MUST be resolved by comparing the node IDs,
with the LSP with the higher node ID being assigned the reservation. with the LSP with the higher node ID being assigned the reservation.
This is consistent with general contention resolution mechanism This is consistent with general contention resolution mechanism
provided in section 3.2 of [RFC3473]. provided in section 4.2 of [RFC3471].
When a node does not support the Availability TLV, the node SHOULD When a node does not support the Bandwidth Availability TLV, the
generate a PathErr message with the error code "Extended Class-Type node should send a PathErr message with error code "Unknown
Error" and the error value "Class-Type mismatch" (see [RFC2205]). Attributes TLV", as specified in [RFC5420]. An LSP could also be set
When a node receives Availability TLVs which mixed of zero index and up in this case if there's enough bandwidth (the availability level
non-zero index, the message MAY be ignored and SHOULD NOT be of the reserved bandwidth is unknown). When a node receives
propagated. When a node receives Availability TLVs (non-zero index) Bandwidth Availability TLVs with a mix of zero index and non-zero
with no matching index value among the bandwidth-TLVs, the message index, the message MUST be ignored and MUST NOT be propagated. When
MAY be ignored and SHOULD NOT be propagated. When a node receives a node receives Bandwidth Availability TLVs (non-zero index) with no
several <bandwidth, availability> pairs, but there're are extra matching index value among the bandwidth-TLVs, the message MUST be
bandwidth-TLVs without matching index Availability-TLV, the extra ignored and MUST NOT be propagated. When a node receives several
bandwidth-TLVs MAY be ignored and SHOULD NOT be propagated. <bandwidth, availability> pairs, but there are extra bandwidth-TLVs
without matching the index of any Availability-TLV, the extra
bandwidth-TLVs MUST be ignored and MUST NOT be propagated.
4. Security Considerations 4. Security Considerations
This document defines an Availability TLV in RSVP-TE signaling used This document defines a Bandwidth Availability TLV in RSVP-TE
in GMPLS network. [RFC3945] notes that authentication in GMPLS signaling used in GMPLS networks. [RFC3945] notes that
systems may use the authentication mechanisms of the component authentication in GMPLS systems may use the authentication
protocols. [RFC5920] provides an overview of security mechanisms of the component protocols. [RFC5920] provides an
vulnerabilities and protection mechanisms for the GMPLS control overview of security vulnerabilities and protection mechanisms for
plane. Especially section 7.1.2 of [RFC5920] discuss the control- the GMPLS control plane. Especially section 7.1.2 of [RFC5920]
plane protection with RSVP-TE by using general RSVP security tools, discusses the control-plane protection with RSVP-TE by using general
limiting the impact of an attack on control-plane resources, and RSVP security tools, limiting the impact of an attack on control-
authentication for RSVP messages. Moreover, the GMPLS network is plane resources, and authentication for RSVP messages. Moreover, the
often considered to be a closed network such that insertion, GMPLS network is often considered to be a closed network such that
modification, or inspection of packets by an outside party is not insertion, modification, or inspection of packets by an outside
possible. party is not possible.
5. IANA Considerations 5. IANA Considerations
IANA maintains registries and sub-registries for RSVP-TE used by IANA maintains registries and sub-registries for RSVP-TE used by
GMPLS. IANA is requested to make allocations from these registries GMPLS. IANA is requested to make allocations from these registries
as set out in the following sections. as set out in the following sections.
5.1 Ethernet Sender TSpec TLVs 5.1 Ethernet Sender TSpec TLVs
IANA maintains a registry of GMPLS parameters called "Generalized IANA maintains a registry of GMPLS parameters called "Generalized
Multi-Protocol Label Switching (GMPLS) Signaling Parameters". Multi-Protocol Label Switching (GMPLS) Signaling Parameters".
IANA has created a sub-registry called "Ethernet Sender TSpec TLVs / IANA has created a sub-registry called "Ethernet Sender TSpec TLVs /
Ethernet Flowspec TLVs" to contain the TLV type values for TLVs Ethernet Flowspec TLVs" to contain the TLV type values for TLVs
carried in the Ethernet SENDER_TSPEC object. The sub-registry needs carried in the Ethernet SENDER_TSPEC object. The sub-registry needs
to be updated to include the Availability TLV which is defined as to be updated to include the Bandwidth Availability TLV which is
follow. This document proposes a suggested value for the defined as follow. This document proposes a suggested value for the
Availability sub-TLV; it is requested that the suggested value be Availability sub-TLV; it is requested that the suggested value be
granted by IANA. granted by IANA.
Type Description Reference Type Description Reference
----- ----------------------------------- --------- ----- -------------------- ---------
0x04 Availability [This ID] 0x04 Bandwidth Availability [This ID]
(Suggested; TBD by IANA)
The registration procedure for this registry is Standards Action as The registration procedure for this registry is Standards Action as
defined in [RFC8126]. defined in [RFC8126].
6. References 6. References
6.1. Normative References 6.1. Normative References
[RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and [RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and
S.Jamin, "Resource ReSerVation Protocol (RSVP) - Version 1 S.Jamin, "Resource ReSerVation Protocol (RSVP) - Version 1
Functional Specification", RFC 2205, September 1997. Functional Specification", RFC 2205, September 1997.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan,
V.,and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP V.,and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001. Tunnels", RFC 3209, December 2001.
[RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching [RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Resource ReserVation Protocol-Traffic (GMPLS) Signaling Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE) Extensions", RFC 3473, January 2003. Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.
[RFC3471] Berger, L., "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Functional Description", RFC 3471,
January 2003.
[RFC5420] Farrel, A., Papadimitriou, D., Vasseur JP., and Ayyangar
A., "Encoding of Attributes for MPLS LSP Establishment
Using Resource Reservation Protocol Traffic Engineering
(RSVP-TE)", RFC 5420, February 2009.
[RFC6003] Papadimitriou, D. "Ethernet Traffic Parameters", RFC 6003, [RFC6003] Papadimitriou, D. "Ethernet Traffic Parameters", RFC 6003,
October 2010. October 2010.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, May 2017. 2119 Key Words", BCP 14, RFC 8174, May 2017.
[IEEE754] IEEE, "IEEE Standard for Floating-Point Arithmetic",IEEE
754-2008, DOI 10.1109/IEEESTD.2008.4610935, 2008,
<http://standards.ieee.org/findstds/standard/754-
2008.html>.
6.2. Informative References 6.2. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997. Requirement Levels", RFC 2119, March 1997.
[RFC8126] Cotton,M. and Leiba,B., and Narten T., "Guidelines for [RFC8126] Cotton,M. and Leiba,B., and Narten T., "Guidelines for
Writing an IANA Considerations Section in RFCs", RFC 8126, Writing an IANA Considerations Section in RFCs", RFC 8126,
June 2017. June 2017.
[RFC3945] Mannie, E., "Generalized Multi-Protocol Label Switching [RFC3945] Mannie, E., "Generalized Multi-Protocol Label Switching
skipping to change at page 9, line 23 skipping to change at page 9, line 47
[RFC8330] H., Long, M., Ye, Mirsky, G., Alessandro, A., Shah, H., [RFC8330] H., Long, M., Ye, Mirsky, G., Alessandro, A., Shah, H.,
"OSPF Traffic Engineering (OSPF-TE) Link Availability "OSPF Traffic Engineering (OSPF-TE) Link Availability
Extension for Links with Variable Discrete Bandwidth", Extension for Links with Variable Discrete Bandwidth",
RFC8330, February 2018 RFC8330, February 2018
7. Appendix: Bandwidth Availability Example 7. Appendix: Bandwidth Availability Example
In a mobile backhaul network, microwave links are very popular for In a mobile backhaul network, microwave links are very popular for
providing connections of last hops. In case of heavy rain providing connections of last hops. In case of heavy rain
conditions, to maintain the link connectivity, the microwave link conditions, to maintain the link connectivity, the microwave link
MAY lower the modulation level since demodulating to a lower may lower the modulation level since moving to a lower modulation
modulation level provides for a lower Signal-to-Noise Ratio (SNR) level provides for a lower Signal-to-Noise Ratio (SNR) requirement.
requirement. This is called adaptive modulation technology [EN 302 This is called adaptive modulation technology [EN 302 217]. However,
217]. However, a lower modulation level also means lower link a lower modulation level also means lower link bandwidth. When link
bandwidth. When link bandwidth is reduced because of modulation bandwidth is reduced because of modulation down-shifting, high-
down-shifting, high-priority traffic can be maintained, while lower- priority traffic can be maintained, while lower-priority traffic is
priority traffic is dropped. Similarly, copper links may change dropped. Similarly, copper links may change their link bandwidth due
their link bandwidth due to external interference. to external interference.
Presuming that a link has three discrete bandwidth levels: Presuming that a link has three discrete bandwidth levels:
The link bandwidth under modulation level 1, e.g., QPSK, is 100 The link bandwidth under modulation level 1, e.g., QPSK, is 100
Mbps; Mbps;
The link bandwidth under modulation level 2, e.g., 16QAM, is 200 The link bandwidth under modulation level 2, e.g., 16QAM, is 200
Mbps; Mbps;
The link bandwidth under modulation level 3, e.g., 256QAM, is 400 The link bandwidth under modulation level 3, e.g., 256QAM, is 400
skipping to change at page 10, line 17 skipping to change at page 10, line 40
from 200 Mbps to 100 Mbps. The probability of Y mm/h rain in the from 200 Mbps to 100 Mbps. The probability of Y mm/h rain in the
local area is 26 minutes in a year. Then the dropped 100 Mbps local area is 26 minutes in a year. Then the dropped 100 Mbps
bandwidth has 99.995% availability. bandwidth has 99.995% availability.
For the 100M bandwidth of the modulation level 1, only the extreme For the 100M bandwidth of the modulation level 1, only the extreme
weather condition can cause the whole system to be unavailable, weather condition can cause the whole system to be unavailable,
which only happens for 5 minutes in a year. So the 100 Mbps which only happens for 5 minutes in a year. So the 100 Mbps
bandwidth of the modulation level 1 owns the availability of bandwidth of the modulation level 1 owns the availability of
99.999%. 99.999%.
There are discrete buckets per availability level. Under the worst
weather conditions, there's only 100 Mbps capacity and that's
99.999% available. It's treated as effectively "always available"
since there's no way to do any better. If the weather is bad but not
the worst weather, modulation level 2 can be used, which gets an
additional 100 Mbps bandwidth (i.e., 200 Mbps total), so there are
100 Mbps in the 99.999% bucket and 100 Mbps in the 99.995% bucket.
In clear weather, modulate level 3 can be used to get 400 Mbps
total, but that's only 200 Mbps more than at modulation level 2, so
99.99% bucket has that "extra" 200 Mbps, and the other two buckets
still have their 100 Mbps each.
Therefore, the maximum bandwidth is 400 Mbps. According to the Therefore, the maximum bandwidth is 400 Mbps. According to the
weather condition, the sub-bandwidth and its availability are shown weather condition, the sub-bandwidth and its availability are shown
as follows: as follows:
Sub-bandwidth (Mbps) Availability Sub-bandwidth (Mbps) Availability
------------------ ------------ ------------------ ------------
200 99.99% 200 99.99%
 End of changes. 29 change blocks. 
88 lines changed or deleted 126 lines changed or added

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