Network Working Group H. Long, M. Ye
Internet Draft Huawei Technologies Co., Ltd
Intended status: Standards Track G. Mirsky
ZTE
A.D'Alessandro
Telecom Italia S.p.A
H. Shah
Ciena
Expires: February 2018 August 8, 2017
Ethernet Traffic Parameters with Availability Information
draft-ietf-ccamp-rsvp-te-bandwidth-availability-07.txt
Abstract
A Packet switching network may contain links with variable bandwidth,
e.g., copper, radio, etc. The bandwidth of such links is sensitive
to external environment. Availability is typically used for
describing the link during network planning. This document
introduces an optional Availability TLV in Resource ReSerVation
Protocol - Traffic Engineer (RSVP-TE) signaling. This extension can
be used to set up a Label Switched Path (LSP) in a Packet Switched
Network (PSN) that contains links with discretely variable
bandwidth.
Status of this Memo
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Table of Contents
1. Introduction ................................................ 3
2. Overview .................................................... 4
3. Extension to RSVP-TE Signaling............................... 4
3.1. Availability TLV........................................ 4
3.2. Signaling Process....................................... 5
4. Security Considerations...................................... 6
5. IANA Considerations ......................................... 6
5.1 Ethernet Sender TSpec TLVs ............................. 6
6. References .................................................. 7
6.1. Normative References.................................... 7
6.2. Informative References.................................. 7
7. Appendix: Bandwidth Availability Example..................... 8
8. Acknowledgments ............................................. 9
Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [RFC2119].
The following acronyms are used in this draft:
RSVP-TE Resource Reservation Protocol-Traffic Engineering
LSP Label Switched Path
PSN Packet Switched Network
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SNR Signal-to-noise Ratio
TLV Type Length Value
LSA Link State Advertisement
1. Introduction
The RSVP-TE specification [RFC3209] and GMPLS extensions [RFC3473]
specify the signaling message including the bandwidth request for
setting up a Label Switched Path in a PSN network.
Some data communication technologies allow seamless change of
maximum physical bandwidth through a set of known discrete values.
The parameter availability [G.827], [F.1703], [P.530] is often used
to describe the link capacity during network planning. The
availability is a time scale, which is a proportion of the operating
time that the requested bandwidth is ensured. A more detailed
example on the bandwidth availability can be found in Appendix A.
Assigning different availability classes to different types of
service over such kind of links provides more efficient planning of
link capacity. To set up an LSP across these links, availability
information is required for the nodes to verify bandwidth
satisfaction and make bandwidth reservation. The availability
information should be inherited from the availability requirements
of the services expected to be carried on the LSP. For example,
voice service usually needs "five nines" availability, while non-
real time services may adequately perform at four or three nines
availability. Since different service types may need different
availabilities guarantees, multiple <availability, bandwidth> pairs
may be required when signaling.
If the availability requirement is not specified in the signaling
message, the bandwidth will be reserved as the highest availability.
For example, the bandwidth with 99.999% availability of a link is
100 Mbps; the bandwidth with 99.99% availability is 200 Mbps. When a
video application requests for 120 Mbps without availability
requirement, the system will consider the request as 120 Mbps with
99.999% availability, while the available bandwidth with 99.999%
availability is only 100 Mbps, therefore the LSP path cannot be set
up. But in fact, video application doesn't need 99.999% availability;
99.99% availability is enough. In this case, the LSP could be set up
if availability is specified in the signaling message.
To fulfill LSP setup by signaling in these scenarios, this document
specifies an Availability TLV. The Availability TLV can be
applicable to any kind of physical links with variable discrete
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bandwidth, such as microwave or DSL. Multiple Availability TLVs
together with multiple Ethernet Bandwidth Profiles can be carried in
the Ethernet SENDER_TSPEC object.
2. Overview
A PSN tunnel may span one or more links in a network. To setup a
Label Switched Path (LSP), a node may collect link information which
is spread in routing message, e.g., OSPF TE LSA message, by network
nodes to get to know about the network topology, and calculate out
an LSP route based on the network topology, and send the calculated
LSP route to signaling to initiate a PATH/RESV message for setting
up the LSP.
In case that there is(are) link(s) with variable discrete bandwidth
in a network, a <bandwidth, availability> requirement list should be
specified for an LSP. Each <bandwidth, availability> pair in the
list means that listed bandwidth with specified availability is
required. The list could be inherited from the results of service
planning for the LSP.
A node which has link(s) with variable discrete bandwidth attached
should contain a <bandwidth, availability> information list in its
OSPF TE LSA messages. The list provides the mapping between the link
nominal bandwidth and its availability level. This information is
used for path calculation by the node(s). The routing extension for
availability can be found in [ARTE].
When a node initiates a PATH/RESV signaling to set up an LSP, the
PATH message should carry the <bandwidth, availability> requirement
list as bandwidth request. Intermediate node(s) will allocate the
bandwidth resource for each availability requirement from the
remaining bandwidth with corresponding availability. An error
message may be returned if any <bandwidth, availability> request
cannot be satisfied.
3. Extension to RSVP-TE Signaling
3.1. Availability TLV
An Availability TLV is defined as a TLV of the Ethernet
SENDEDR_TSPEC object [RFC6003] in this document. The Ethernet
SENDER_TSPEC object MAY include more than one Availability TLV. The
Availability TLV has the following format:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Index | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Availability |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Availability TLV
Index (1 octet):
The Availability TLV MUST come along with Ethernet Bandwidth
Profile TLV. If the bandwidth requirements in the multiple
Ethernet Bandwidth Profile TLVs have different Availability
requirements, multiple Availability TLVs SHOULD be carried. In
such a case, the Availability TLV has one to one correspondence
with Ethernet Bandwidth Profile TLV by having the same value of
Index field. If all the bandwidth requirements in the Ethernet
Bandwidth Profile have the same Availability requirement, one
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
and MUST be ignored when received.
Availability (4 octets): a 32-bit floating number describes the
decimal value of availability requirement for this bandwidth
request. The value MUST be less than 1and is usually expressed in
the value of 0.99/0.999/0.9999/0.99999.
3.2. Signaling Process
The source node initiates PATH messages which carry a number of
bandwidth request information, including one or more Ethernet
Bandwidth Profile TLVs and one or more Availability TLVs. Each
Ethernet Bandwidth Profile TLV corresponds to an availability
parameter in the Availability TLV.
The intermediate and destination nodes check whether they can
satisfy the bandwidth requirements by comparing each bandwidth
requirement inside the SENDER_TSPEC objects with the remaining link
sub-bandwidth resource with respective availability guarantee on the
local link when received the PATH message.
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o If all <bandwidth, availability> requirements can be
satisfied (the requested bandwidth under each availability
parameter is smaller than or equal to the remaining bandwidth
under the corresponding availability parameter on its local
link), it SHOULD reserve the bandwidth resource from each
remaining sub-bandwidth portion on its local link to set up
this LSP. Optionally, the higher availability bandwidth can be
allocated to lower availability request when the lower
availability bandwidth cannot satisfy the request.
o If at least one <bandwidth, availability> requirement cannot
be satisfied, it SHOULD generate PathErr message with the error
code "Admission Control Error" and the error value "Requested
Bandwidth Unavailable" (see [RFC2205]).
If two LSPs request for the bandwidth with the same availability
requirement, a way to resolve the contention is comparing the node
ID, the node with the higher node ID will win the contention. More
details can be found in [RFC3473].
If a node does not support Availability TLV, it SHOULD generate
PathErr message with the error code "Extended Class-Type Error" and
the error value "Class-Type mismatch" (see [RFC2205]).
4. Security Considerations
This document does not introduce new security considerations to the
existing RSVP-TE signaling protocol. [RFC5920] provides an overview
of security vulnerabilities and protection mechanisms for the GMPLS
control plane.
5. IANA Considerations
IANA maintains registries and sub-registries for RSVP-TE used by
GMPLS. IANA is requested to make allocations from these registries
as set out in the following sections.
5.1 Ethernet Sender TSpec TLVs
IANA maintains a registry of GMPLS parameters called "Generalized
Multi-Protocol Label Switching (GMPLS) Signaling Parameters".
IANA has created a sub-registry called "Ethernet Sender TSpec TLVs /
Ethernet Flowspec TLVs" to contain the TLV type values for TLVs
carried in the Ethernet SENDER_TSPEC object. The sub-registry is
needed to be updated to include the Availability TLV which is
defined as follow. This document proposes a suggested value for the
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Availability sub-TLV; it is recommended that the suggested value be
granted by IANA.
Type Description Reference
----- ----------------------------------- ---------
0x04 Availability [This ID]
The registration procedure for this registry is Standards Action as
defined in [RFC8126].
6. References
6.1. Normative References
[RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and
S.Jamin, "Resource ReSerVation Protocol (RSVP) - Version 1
Functional Specification", RFC 2205, September 1997.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan,
V.,and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.
[RFC6003] Papadimitriou, D. "Ethernet Traffic Parameters", RFC 6003,
October 2010.
6.2. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
[RFC8126] Cotton,M. and Leiba,B., and Narten T., "Guidelines for
Writing an IANA Considerations Section in RFCs",
RFC 8126, June 2017.
[RFC5920] Fang, L., "Security Framework for MPLS and GMPLS Networks",
RFC 5920, July 2010.
[G.827] ITU-T Recommendation, "Availability performance parameters
and objectives for end-to-end international constant bit-
rate digital paths", September, 2003.
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[F.1703] ITU-R Recommendation, "Availability objectives for real
digital fixed wireless links used in 27 500 km
hypothetical reference paths and connections", January,
2005.
[P.530] ITU-R Recommendation," Propagation data and prediction
methods required for the design of terrestrial line-of-
sight systems", February, 2012
[EN 302 217] ETSI standard, "Fixed Radio Systems; Characteristics
and requirements for point-to-point equipment and
antennas", April, 2009
[ARTE] H., Long, M., Ye, Mirsky, G., Alessandro, A., Shah, H.,
"OSPF Routing Extension for Links with Variable Discrete
Bandwidth", Work in Progress, October, 2016
7. Appendix: Bandwidth Availability Example
In mobile backhaul network, microwave links are very popular for
providing connection of last hops. In case of heavy rain, to
maintain the link connectivity, the microwave link MAY lower the
modulation level since demodulating the lower modulation level needs
a lower Signal-to-Noise Ratio (SNR). This is called adaptive
modulation technology [EN 302 217]. However, a lower modulation
level also means lower link bandwidth. When link bandwidth is
reduced because of modulation down-shifting, high-priority traffic
can be maintained, while lower-priority traffic is dropped.
Similarly, the copper links MAY change their link bandwidth due to
external interference.
Presuming that a link has three discrete bandwidth levels:
The link bandwidth under modulation level 1, e.g., QPSK, is 100 Mbps;
The link bandwidth under modulation level 2, e.g., 16QAM, is 200
Mbps;
The link bandwidth under modulation level 3, e.g., 256QAM, is 400
Mbps.
In sunny day, the modulation level 3 can be used to achieve 400 Mbps
link bandwidth.
A light rain with X mm/h rate triggers the system to change the
modulation level from level 3 to level 2, with bandwidth changing
from 400 Mbps to 200 Mbps. The probability of X mm/h rain in the
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local area is 52 minutes in a year. Then the dropped 200 Mbps
bandwidth has 99.99% availability.
A heavy rain with Y(Y>X) mm/h rate triggers the system to change the
modulation level from level 2 to level 1, with bandwidth changing
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
bandwidth has 99.995% availability.
For the 100M bandwidth of the modulation level 1, only the extreme
weather condition can cause the whole system unavailable, which only
happens for 5 minutes in a year. So the 100 Mbps bandwidth of the
modulation level 1 owns the availability of 99.999%.
In a word, the maximum bandwidth is 400 Mbps. According to the
weather condition, the sub-bandwidth and its availability are shown
as follows:
Sub-bandwidth(Mbps) Availability
------------------ ------------
200 99.99%
100 99.995%
100 99.999%
8. Acknowledgments
The authors would like to thank Khuzema Pithewan, Lou Berger, Yuji
Tochio, Dieter Beller, and Autumn Liu for their comments on the
document.
Authors' Addresses
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Hao Long
Huawei Technologies Co., Ltd.
No.1899, Xiyuan Avenue, Hi-tech Western District
Chengdu 611731, P.R.China
Phone: +86-18615778750
Email: longhao@huawei.com
Min Ye (editor)
Huawei Technologies Co., Ltd.
No.1899, Xiyuan Avenue, Hi-tech Western District
Chengdu 611731, P.R.China
Email: amy.yemin@huawei.com
Greg Mirsky (editor)
ZTE
Email: gregimirsky@gmail.com
Alessandro D'Alessandro
Telecom Italia S.p.A
Email: alessandro.dalessandro@telecomitalia.it
Himanshu Shah
Ciena Corp.
3939 North First Street
San Jose, CA 95134
US
Email: hshah@ciena.com
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