SPRING Working Group Madhukar Anand
Internet-Draft Sanjoy Bardhan
Intended Status: Informational Ramesh Subrahmaniam
Infinera Corporation
Jeff Tantsura
Individual
Utpal Mukhopadhyaya
Equinix Inc
Expires: December 28, 2017 June 26, 2017
Packet-Optical Integration in Segment Routing
draft-anand-spring-poi-sr-03
Abstract
This document illustrates a way to integrate a new class of nodes and
links in segment routing to represent transport networks in an opaque
way into the segment routing domain. An instance of this class would
be optical networks that are typically transport centric. In the IP
centric network, this will help in defining a common control protocol
for packet optical integration that will include optical paths as
'transport segments' or sub-paths as an augmentation to the defined
extensions of segment routing. The transport segment option also
defines a general mechanism to allow for future extensibility of
segment routing into non-packet domains.
Requirements Language
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].
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as
Internet-Drafts.
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
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http://www.ietf.org/1id-abstracts.html
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Copyright and License Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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publication of this document. Please review these documents
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Reference Taxonomy . . . . . . . . . . . . . . . . . . . . . . 4
3. Use case - Packet Optical Integration . . . . . . . . . . . . . 5
4. Mechanism overview . . . . . . . . . . . . . . . . . . . . . . 8
5. PCEP-LS extensions for supporting the transport segment . . . 8
6. OSPF extensions for supporting the transport segment . . . . . 10
7. OSPFv3 extensions for supporting the transport segment . . . . 11
8. IS-IS extensions for supporting the transport segment . . . . 12
9. BGP-LS extensions for supporting the transport segment . . . . 14
10. Note about Transport Segments and Scalability . . . . . . . . 17
11. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
12. Security Considerations . . . . . . . . . . . . . . . . . . . 17
13 IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
13.1 PCEP . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
13.2 OSPF . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
13.3 OSPFv3 . . . . . . . . . . . . . . . . . . . . . . . . . . 18
13.4 IS-IS . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
13.5 BGP-LS . . . . . . . . . . . . . . . . . . . . . . . . . . 18
14 References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
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14.1 Normative References . . . . . . . . . . . . . . . . . . . 19
14.2 Informative References . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20
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1 Introduction
Packet and optical transport networks have evolved independently with
different control plane mechanisms that have to be provisioned and
maintained separately. Consequently, coordinating packet and optical
networks for delivering services such as end-to-end traffic
engineering or failure response has proved challenging. To address
this challenge, a unified control and management paradigm that
provides an incremental path to complete packet-optical integration
while leveraging existing signaling and routing protocols in either
domains is needed. This document introduces such a paradigm based on
Segment Routing (SR) [I-D.ietf-spring-segment-routing].
This document introduces a new type of segment, Transport segment.
Transport segment can be used to model abstracted paths through the
optical transport domain and integrate it with the packet network for
delivering end-to-end services. In addition, this also introduces a
notion of a Packet optical gateway (POG). These are nodes in the
network that map packet services to the optical domain that originate
and terminate these transport segments. Given a transport segment, a
POG will expand it to a path in the optical transport network.
The concept of POG introduced here allows for multiple instantiations
of the concept. In one case, the packet device is distinct from the
optical transport device, and the POG is a logical entity that spans
these two devices. In this case, the POG functionality is achieved
with the help of external coordination between the packet and optical
devices. In another case, the packet and optical components are
integrated into one physical device, and the co-ordination required
for functioning of the POG is performed by this integrated device.
It must be noted that in either case, it is the packet/optical data
plane that is either disaggregated or integrated. Control of the
devices can be logically centralized or distributed in either
scenario. The focus of this document is to define the logical
functions of a POG without going into the exact instantiations of the
concept.
2. Reference Taxonomy
POG - Packet optical gateway Device
SR Edge Router - The Edge Router which is the ingress device
CE - Customer Edge Device that is outside of the SR domain
PCE - Path Computation Engine
Controller - A network controller
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3. Use case - Packet Optical Integration
Many operators build and operate their networks that are both multi-
layer and multi-domain. Services are built around these layers and
domains to provide end-to-end services. Due to the nature of the
different domains, such as packet and optical, the management and
service creation has always been problematic and time consuming. With
segment routing, enabling a head-end node to select a path and embed
the information in the packet is a powerful construct that would be
used in the Packet Optical Gateways (POG). The path is usually
constructed for each domain that may be manually derived or through a
stateful PCE which is run specifically in that domain.
P5
P1 _ .-'-._ ,'P4
`._ .-' `-. ,'
`. _.-' `-._ ,'
`-. .-' `-. ,'
P2`.-'--------------------------`-.- P3
|\ /|
| \ / | Packet
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
| \ / |
| \ / | Transport
| \ / |
| ................../ |
| ,'O2 O3`. |
| ,' `. |
|,' `. |
O1\ | O4
\ ,'
\ ,'
.......................-
O6 O5
Figure 1: Representation of a packet-optical path
In Figure 1 above, the nodes represent a packet optical network.
P1,...,P5 are packet devices. Nodes P2 and P3 are connected via optical
network comprising of nodes O1,...,O6. Nodes P2 and P3 are POGs that
communicate with other packet devices and also with the devices in the
optical transport domain. In defining a link in the packet domain
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between P2 and P3, we will need to specify both the nodes and the links
in the optical transport domain that establish this link.
To leverage segment routing to define a service between P1 and P4, the
ingress node P1 would append all outgoing packets in a SR header
consisting of the SIDs that constitute the path. In the packet domain
this would mean P1 would send its packets towards P4 using a segment
list {P2, P3, P4} or {P2, P5, P3, P4} as the case may be. The operator
would need to use a different mechanism in the optical domain to set up
the optical paths comprising the nodes O1, O2 and O3. Each POG would
announce the active optical path as a transport segment - for example,
the optical path {O1, O2, O3} could be represented as a label Om and the
optical path {O2, O3} could be represented as a transport label On. Both
Om and On will be advertised by Packet node P1. These paths are not
known to the packet SR domain and is only relevant to the optical domain
D between P2 and P3. A PCE that is run in Domain D would be
responsible for calculating paths corresponding to label Om and On. The
expanded segment list would read as {P2, Om, P3, P4} or {P2, On, P3,
P4}. It is to be noted that there are other possible paths between P2
and P3 in the optical domain involving optical nodes O5, O6, and O4.
There is no requirement that every path between P2 and P3 be represented
as transport segments. A discussion on transport segments and
scalability can be found in Section 10.
Use-case examples of transport segments.
1. Consider the scenario where there are multiple fibers between two
packet end points. The network operator may choose to route packet
traffic on the first fiber, and reserve the second fiber only to
maintenance or low priority traffic.
2. As a second use-case, consider the case where the packet end points
are connected by optical transport provided by two different service
providers. The packet operator wants to preferentially route traffic
over one of the providers and use the second provider as a backup.
3. Finally, let the packet end points be connected by optical paths that
lie in different geographies. For instance, one optical transport path
may lie completely in one country while the other optical transport path
transits another country. Weather, tariffs, security considerations and
other factors may determine how the packet operator wants to route
different types of traffic on this network.
All of the above use-cases can be supported by first mapping distinct
optical transport paths to different transport segments and then,
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depending on the need, affixing appropriate transport segment identifier
to the specific packet to route it appropriately through the transport
domain.
+------------------------+
| |
+--------------+----' PCE or Controller |----+---------------+
| | | | | |
| | +------------------------+ | |
| | | |
| | .-----. | |
| | ( ) | |
+-------+ +-------+ .--( )--. +-------+ +-------+
| SR | |Packet | ( ) |Packet | | SR |
| Edge | |Optical|-( Optical Transport )_ |Optical| | Edge |
|Router | ... |Gateway| ( Domain ) |Gateway| ... |Router |
+---+.--+ +-------+ ( ) +-------+ +---+.--+
| '--( )--' |
,--+. ( ) ,-+-.
( CE ) '-----' ( CE )
`---' `---'
Figure 3. Reference Topology for Transport Segment Mechanism
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4. Mechanism overview
The current proposal assumes that the SR domains run standard IGP
protocols to discover the topology and distribute labels without any
modification. There are also no modifications to the control plane
mechanisms in the Optical transport domains. For example, the optical
paths may be setup using a domain-specific controller or PCE based on
requirements from the packet domain (such as bandwidth, QoS, latency
and cost). The mechanism for supporting the transport segment in the
packet domain is as follows.
1. Firstly, the Packet Optical Gateway (POG) devices announce
themselves in the SR domain. This is indicated by advertising a new
SR node capability flag. The exact extensions to support this
capability are described in the subsequent sections of this
document.
2. Then, the POG devices announce paths to other POGs through the
optical transport domain as a transport segment (transport segment
binding SID) in the SR domain. The paths are announced with an
appropriate optical transport domain ID, and a label (Packet-Optical
Label) to be used to bind to the transport segment. The appropriate
IGP segment routing extensions to carry this information is described
in the subsequent sections of this document.
3. The transport segment can also optionally be announced with a
set of attributes that characterizes the path in the optical
transport domain between the two POG devices. For instance, those
attributes could define the OTN mapping used (e.g., ODU4,
ODU3,ODU3e1....ODU1), timeslots (1-8 or 4,6,7 or 1-2,5), or optical
path protection schemes.
4. The POG device is also responsible for programming its
forwarding table to map every transport segment label entry into an
appropriate forwarding action relevant in the optical domain, such as
mapping it to a label-switched path.
5. The transport segment is communicated to the PCE or Controller
using extensions to BGP-LS or PCEP-LS as described in subsequent
sections of this document.
6. Finally, the PCE or Controller then uses the transport segment
label to influence the path leaving the SR domain into the optical
domain, thereby defining the end-to-end path for a given service.
5. PCEP-LS extensions for supporting the transport segment
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To communicate the Packet-Optical Gateway capability of the device,
we introduce a new PCEP capabilities TLV is defined as
follows(extensions to [I-D.draft-sivabalan-pce-segment-routing]):
Value Meaning Reference
-------- ------------------------------------ -----------------
27 TRANSPORT-SR-PCE-CAPABILITY This document
A new type of TLV to accommodate a transport segment is defined
by extending Binding SIDs [I-D.draft-sivabalan-pce-binding-label-sid-01]
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Binding Type (BT) | Domain ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Binding Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Transport Segment Sub TLVs (variable length) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Type: TBD, suggested value 32
Length: variable.
Binding Type: 0 or 1 as defined in
[I-D.draft-sivabalan-pce-binding-label-sid-01]
Domain ID: An identifier for the transport domain
Binding Value: is the transport segment label
Transport Segment Sub TLVs: TBD
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IANA will be requested to allocate a new TLV type (recommended value
is 32) for TRANSPORT-SEGMENT-BINDING-TLV as specified in this document:
1 Transport Segment Label (This document)
6. OSPF extensions for supporting the transport segment
To communicate the Packet-Optical Gateway capability of the
device, we introduce an new optical informational capability bit in the
Router Information capabilities TLV (as defined in [RFC4970]).
Bit-24 - Optical - If set, then the router is capable of performing
Packet Optical Gateway function.
Further, a new OSPF sub-TLV (similar to the ERO SubTLV) of SID/Label
Binding Sub-TLV (TRANSPORT-SEGMENT-BINDING-SUBTLV) to carry the
transport segment label is defined as follows.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Domain ID | Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Packet-Optical Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Transport Segment Sub TLVs (variable length) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Type : TBD, Suggested Value 9
Length: variable.
Domain ID: An identifier for the transport domain
Flags: 1 octet field of following flags:
V - Value flag. If set, then the optical label carries a value.
By default the flag is SET.
L - Local. Local Flag. If set, then the value/index carried by
the Adj-SID has local significance. By default the flag is SET.
0 1 2 3 4 5 6 7
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+-+-+-+-+-+-+-+-+
|V|L|
+-+-+-+-+-+-+-+-+
Packet-Optical Label : according to the V and L flags, it contains
either:
* A 3 octet local label where the 20 rightmost bits are
used for encoding the label value. In this case the V and
L flags MUST be set.
* A 4 octet index defining the offset in the label space
advertised by this router. In this case V and L flags MUST
be unset.
Transport Segment Sub TLVs: TBD
Multiple TRANSPORT-SEGMENT-BINDING-SUBTLV MAY be associated with a pair
of POG devices to represent multiple paths within the optical domain
7. OSPFv3 extensions for supporting the transport segment
To communicate the Packet-Optical Gateway capability of the
device, we introduce an new optical informational capability bit in the
Router Information capabilities TLV (as defined in [RFC4970]).
Bit-24 - Optical - If set, then the router is capable of performing
Packet Optical Gateway function.
Further, a new OSPFv3 sub-TLV similar to the ERO SubTLV) of SID/Label
Binding Sub-TLV (TRANSPORT-SEGMENT-BINDING-SUBTLV) to carry the
transport segment label is defined as follows.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Domain ID | Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Packet-Optical Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Transport Segment Sub TLVs (variable length) ~
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Type : TBD,Suggested Value 12
Length: variable.
Domain ID: An identifier for the transport domain
Flags: 1 octet field of following flags:
V - Value flag. If set, then the optical label carries a value.
By default the flag is SET.
L - Local. Local Flag. If set, then the value/index carried by
the Adj-SID has local significance. By default the flag is SET.
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|V|L|
+-+-+-+-+-+-+-+-+
Packet-Optical Label : according to the V and L flags, it contains
either:
* A 3 octet local label where the 20 rightmost bits are
used for encoding the label value. In this case the V and
L flags MUST be set.
* A 4 octet index defining the offset in the label space
advertised by this router. In this case V and L flags MUST
be unset.
Transport Segment Sub TLVs: TBD
Multiple TRANSPORT-SEGMENT-BINDING-SUBTLV MAY be associated with a pair
of POG devices to represent multiple paths within the optical domain
8. IS-IS extensions for supporting the transport segment
To communicate the Packet-Optical Gateway capability of the device, we
introduce a new flag O in the SR Node Capabilities sub-TLV:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|I|V|H|O| |
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+-+-+-+-+-+-+-+-+
I, V, H flags are defined in [I-D.ietf-isis-segment-routing-extensions]
O-Flag: If set, then the router is capable of performing Packet
Optical Gateway function.
Further, a new IS-IS sub-TLV (similar to the ERO SubTLV) of SID/Label
Binding Sub-TLV (TRANSPORT-SEGMENT-BINDING-SUBTLV) to carry the
transport segment label is defined as follows.
First, we define the O flag in the SID/Label Binding TLV
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|F|M|S|D|A|O| |
+-+-+-+-+-+-+-+-+
F, M, S, D, and A flags: are defined in [I-D.ietf-isis-segment-routing
-extensions]
O-Flag: If set, then the F flag, Range, Prefix Length FEC Prefix, must
be ignored in the SID/Label Binding TLV
Secondly, we define the SubTLV of the SID/Label Binding Sub-TLV:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Domain ID | Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Packet-Optical Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Transport Segment Sub TLVs (variable length) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Type : TBD, Suggested Value 151
Length: variable.
Domain ID: An identifier for the transport domain
Flags: 1 octet field of following flags:
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V - Value flag. If set, then the optical label carries a value.
By default the flag is SET.
L - Local. Local Flag. If set, then the value/index carried by
the Adj-SID has local significance. By default the flag is SET.
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|V|L|
+-+-+-+-+-+-+-+-+
Packet-Optical Label : according to the V and L flags, it contains
either:
* A 3 octet local label where the 20 rightmost bits are
used for encoding the label value. In this case the V and
L flags MUST be set.
* A 4 octet index defining the offset in the label space
advertised by this router. In this case V and L flags MUST
be unset.
Transport Segment Sub TLVs: TBD
Multiple TRANSPORT-SEGMENT-BINDING-SUBTLV MAY be associated with a pair
of POG devices to represent multiple paths within the optical domain
with perhaps different characteristics.
9. BGP-LS extensions for supporting the transport segment
9.1 Node Attribuites TLV
To communicate the Packet-Optical Gateway capability of the
device, we introduce an new optical informational capability
the following new Node Attribute TLV is defined:
+-----------+----------------------------+----------+---------------+
| TLV Code | Description | Length | Section |
| Point | | | |
+-----------+----------------------------+----------+---------------+
| 1172 | SR-Optical-Node-Capability | variable | |
| | TLV | | |
+-----------+----------------------------+----------+---------------+
Table 1: Node Attribute TLVs
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These TLVs can ONLY be added to the Node Attribute associated with
the node NLRI that originates the corresponding SR TLV.
9.2 SR-Optical-Node-Capability TLV
The SR Capabilities sub-TLV has following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Type : TBD, Suggested Value 1157
Length: variable.
Flags: The Flags field currently has only one bit defined. If the bit
is set it has the capability of an Packet Optical Gateway.
9.3 Prefix Attribute TLVs
The following Prefix Attribute Binding SID Sub-TLVs have been added:
+------------+-------------------------+----------+-----------------+
| TLV Code | Description | Length | Section |
| Point | | | |
+------------+-------------------------+----------+-----------------+
| 1173 | TRANSPORT-SEGMENT-SID | 12 | |
| | | | |
+------------+-------------------------+----------+-----------------+
Table 4: Prefix Attribute - Binding SID Sub-TLVs
The Transport segment TLV allows a node to advertise an transport
segment within a single IGP domain. The transport segment SID TLV
TRANSPORT-SEGMENT-TLV has the following format:
9.3.1 Transport Segment SID Sub-TLV
Further, a new sub-TLV (similar to the IPV4 ERO SubTLV) of
Binding SID Sub-TLV (TRANSPORT-SEGMENT-BINDING-SUBTLV) to carry the
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transport segment label is defined as follows.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Domain ID | Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Packet-Optical Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Transport Segment Sub TLVs (variable length) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Type : TBD
Length: variable.
Domain ID: An identifier for the transport domain
Flags: 1 octet field of following flags:
V - Value flag. If set, then the optical label carries a value.
By default the flag is SET.
L - Local. Local Flag. If set, then the value/index carried by
the Adj-SID has local significance. By default the flag is SET.
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|V|L|
+-+-+-+-+-+-+-+-+
Packet-Optical Label : according to the V and L flags, it contains
either:
* A 3 octet local label where the 20 rightmost bits are
used for encoding the label value. In this case the V and
L flags MUST be set.
* A 4 octet index defining the offset in the label space
advertised by this router. In this case V and L flags MUST
be unset.
Transport Segment Sub TLVs: TBD
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Multiple TRANSPORT-SEGMENT-TLV MAY be associated with a pair
of POG devices to represent multiple paths within the optical domain
10. Note about Transport Segments and Scalability
In most operational scenarios, there would be multiple, distinct paths
between the POGs. There is no requirement that every distinct path in
the optical domain be advertised as a separate transport segment.
Transport segments are designed to be consumed in the packet domain,
and the correspondence between transport segments and exact paths in
the optical domain are determined by their utility to the packet world.
Therefore, the number of transport segments is to be determined by the
individual packet-optical use-case. The number of actual paths in the
optical domain between the POG is expected to be large (counting the
number of active and passive devices in the optical network), it is
likely that multiple actual paths are to be advertised as one transport
segment. Of course, in the degenerate case, it is possible that there
is a one-to-one correspondence between an optical path and a transport
segment. Given this view of network operation, the POG is not expected
to handle a large number of transport segments (and identifiers). This
framework does leave open the possibility of handling a large number
of transport segments in future. For instance, a hierarchical
partitioning of the optical domain along with stacking of multiple
transport segment identifiers could be explored towards reducing
the overall number of transport segment identifiers.
11. Summary
The motivation for introducing a new type of segment - transport
segment - is to integrate transport networks with the segment routing
domain and expose characteristics of the transport domain into the
packet domain. An end-to-end path across packet and transport domains
can then be specified by attaching appropriate SIDs to the packet.
An instance of transport segments has been defined here for optical
networks, where paths between packet-optical gateway devices has been
abstracted using binding SIDs. Extensions to various protocols to
announce the transport segment have been proposed in this document.
12. Security Considerations
This document does not introduce any new security considerations.
13 IANA Considerations
This documents request allocation for the following TLVs and subTLVs.
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13.1 PCEP
Packet-Optical Gateway capability of the device
Value Meaning Reference
-------- ------------------------------------ -----------------
27 TRANSPORT-SR-PCE-CAPABILITY This document
A new type of TLV to accommodate a transport segment is defined
by extending Binding SIDs [I-D.draft-sivabalan-pce-binding-label-sid-01]
Value Description Reference
32 TRANSPORT-SR-PCEP-TLV This document
This document requests that a registry is created to manage the value
of the Binding Type field in the TRANSPORT-SR-PCEP TLV.
Value Description Reference
1 Transport Segment Label This document
13.2 OSPF
Transport-Segment SubTLV of OSPF Extended Prefix LSA
Value Description Reference
9 TRANSPORT-SR-OSPF-SUBTLV This document
13.3 OSPFv3
Transport-Segment SubTLV of OSPFv3 Extend-LSA Sub-TLV registry
Value Description Reference
12 TRANSPORT-SR-OSPFv3-SUBTLV This document
13.4 IS-IS
Transport-Segment SubTLV of Segment Identifier / Label Binding TLV
Value Description Reference
151 TRANSPORT-SR-ISIS-SUBTLV This document
13.5 BGP-LS
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Node Attributes TLV:
Value Description Reference
1172 TRANSPORT-SR-BGPLS-CAPABILITY This document
Prefix Attribute Binding SID SubTLV:
Value Description Reference
1173 TRANSPORT-SR-BGPLS-TLV This document
14 References
14.1 Normative References
[I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
and r. rjs@rob.sh, "Segment Routing Architecture", draft-
ietf-spring-segment-routing-04 (work in progress), July
2015.
[I-D.ietf-isis-segment-routing-extensions]
Previdi, S., Filsfils, C., Bashandy, A., Gredler, H.,
Litkowski, S., Decraene, B., and J. Tantsura, "IS-IS
Extensions for Segment Routing", draft-ietf-isis-segment-
routing-extensions-05 (work in progress), June 2015.
[I-D.ietf-ospf-segment-routing-extensions]
Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
Extensions for Segment Routing", draft-ietf-ospf-segment-
routing-extensions-05 (work in progress), June 2015.
[RFC4915] L. Nguyen, P. Psenak, S. Mirtorabi, P. Pillay-Esnault, and
A. Roy, "Multi-Topology (MT) Routing in OSPF.", RFC4915,
<http://tools.ietf.org/html/rfc4915>.
[I-D.ietf-ospf-ospfv3-segment-routing-extensions]
Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
Shakir, R., Henderickx, W., and J. Tantsura, "OSPFv3
Extensions for Segment Routing", draft-ietf-ospf-ospfv3-
segment-routing-extensions-03 (work in progress), June
2015.
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[I-D.ietf-idr-ls-distribution]
Gredler, H., Medved, J., Previdi, S., Farrel, A., and S.
Ray, "North-Bound Distribution of Link-State and TE
Information using BGP", draft-ietf-idr-ls-distribution-13
(work in progress), October 2015.
[RFC4970] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
S. Shaffer, "Extensions to OSPF for Advertising Optional
Router Capabilities", RFC 4970, DOI 10.17487/RFC4970, July
2007, <http://www.rfc-editor.org/info/rfc4970>.
[I-D.sivabalan-pce-binding-label-sid]
Sivabalan, S., Filsfils, C., Previdi, S., Tantsura, J.,
Hardwick, J., and M. Nanduri, "Carrying Binding Label/
Segment-ID in PCE-based Networks.", draft-sivabalan-pce-
binding-label-sid-01 (work in progress), March 2016.
[I-D.ietf-pce-segment-routing]
Sivabalan, S., Medved, J., Filsfils, C., Crabbe, E.,
Lopez, V., Tantsura, J., Henderickx, W., and J. Hardwick,
"PCEP Extensions for Segment Routing", draft-ietf-pce-
segment-routing-07 (work in progress), March 2016.
14.2 Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
Authors' Addresses
Madhukar Anand
Infinera Corporation
169 W Java Dr, Sunnyvale, CA 94089
Email: manand@infinera.com
Sanjoy Bardhan
Infinera Corporation
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169 W Java Dr, Sunnyvale, CA 94089
Email: sbardhan@infinera.com
Ramesh Subrahmaniam
Infinera Corporation
169 W Java Dr, Sunnyvale, CA 94089
Email: RSubrahmaniam@infinera.com
Jeff Tantsura
Email: jefftant.ietf@gmail.com
Utpal Mukhopadhyaya
Equinix Inc
1188 E. Arques, Sunnyvale, CA 94085
Email: umukhopadhyaya@equinix.com
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