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Discovery
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Neighbor Discovery
Motivations and previous approaches
Data Plane Discovery
Functionality
OIF UNI Discovery
G.7714.1 Discovery
Control Plane Discovery
Functionality
GMPLS LMP
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Discovery Motivation
Who is on the other side of the link? Analogy: The human hello protocol
Hello, Im Mr. Blue
Hi, Mr. Blue, Im Ms.
Orange
Nice to meet you Ms.
Orange.
Let me find out
who that is
Its Ms. Orange
and she got my
name right.
Let me double
check that I got
her name right
Its Mr. Blue. Lets tell him who
I am and check his name.
Confirmed that Mr. Blue has
got my name right.
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But is it worth the effort?
Early days of optical networking very few fibersand no standard protocols for this function No.
Current technology lots of fibers Yes!
With commerciallyavailable modern
DWDM systems, one
long-haul fiber pair can
contain more than 100
channels, which get
broken out intoindividual fiber pairs at
end systems and
regenerators.
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OC-48 lines
OC-48 lines
Edge Equipment #1
Edge Equipment #2
Edge Equipment #N
Edge Equipment #N
Edge Equipment #N
Edge Equipment #N
Edge Equipment #N
Edge Equipment #N
Neighbor Discovery (Why bother?)
A single box can have lots of neighbors! Modern SONET/SDH and WDM equipment
can support many ports!
256 ports of OC-48
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Inconsistent Wiring Issues
Consider a bidirectional 1+1 fiber pairWorks fine under normal conditions
Works fine if we lose a fiber, 1+1 protection.
Maintenance operation: Replace bad fiber
Box A Box B
Port 1
Port 2
Port 12
Port 13
Conduit
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Inconsistent Wiring Problems
Undetected miss-wiringBig problem we just pulled the wrong fiber!!!
Now Box A cant hear from Box B.
Box A Box B
Port 1
Port 2
Port 12
Port 13
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Why do Neighbor Discovery?
Allows automatic inventory of physicallinks between nodes
Can determine inconsistent physical wiring
Allows automatic identification of node-pair neighbors
Supports accurate neighbor link information
for use in routing and signaling
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Existing Neighbor Discovery Protocols
A subclass of IP routing protocols contain ahello sub-protocol.
These are known as Interior Gateway Protocols
(IGPs).The most widely used IGPs are OSPFv2 and
IS-IS
OSPFv2 is documented in RFC2328 and is
available from www.ietf.org
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OSPFs Hello Protocol
Neighbor Discovery (bi-directional communications)
Designated Router Election for LANs
Dead Router Detection
OSPF Hello
packet is
carried in an
IP datagram
Version # Type = 1 (hello) Packet length
Router ID
Area ID
Checksum AuType
Authentication
Authentication
Network Mask
HelloInterval (in seconds) Options Rtr Pri
RouterDeadInterval (in seconds)
Designated Router
Backup Designated Router
Neighbor Router ID
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OSPFs Hello Protocol
Neighbor State Machine
Down Attempt
Init 2-Way
Start
Hello Received
Hello Received
1-Way Received
2-Way Received
Keep saying hellountil something
happens...
Ive received ahello but dontknow if they
know me.
I know them and
they know me.
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A Solution Exists, can we go home?
No, transport networks (optical in particular)have two complicating factors:
Layers in transport networks
Both in WDM and TDM systems makes thequestion a bit more complicated.
Separation of Control and Data Planes
Further complicates things and gives us more todiscover
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Layers in WDM Networks
Optical
Amplifier #1
Optical
Amplifier #2
Optical Add/
Drop
multiplexor
Optical
Multiplexor
Optical De-
multiplexor
= Optical Fiber
= Optical Support Channel
for Transport layer
= Optical Support Channel
for multiplex layer
OCh
OMS
OTS OTS OTS
OCh
OMS
OTS
OCh
OMS
OTS
Optical Channel
Optical Multiplex
SectionOptical Transport
Section
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Layers in TDM Networks
Regenerator
(3R) #1
Regenerator
(3R) #2
TDM de-
multiplexor
TDM
Multiplexor
= Optical Fiber
= Regenerator section overhead
= Multiplex section (line) overhead
= User traffic (path layer)
= Unused time slots
Path
MS
RS RS RS
Path
MS
RS
TDM Path
Multiplex Section
Regenerator
Section
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SONET/SDH Layers
PTE TCTE LTE LTE TCTE PTESTE STE
Section Section Section Section Section Section Section
Line LineLine LineLine
Tandem Connection
(optional)
STS Path
VT Path
STS Path
Tandem Connection
(optional)
Line
Section
Physical
Lower order
Virtual Containers
Higher order
Virtual Containers
Tandem Connection
(optional)
Multiplex Section
Regenerator Section
Physical
(a) SONET (b) SDH
50Mbps 40Gbps
1.5Mbps 6Mbps
Multiplexing here
J0 section trace
J1 Path traceMultiplexing here
J2 VT trace
No Line trace
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Neighbor Discovery at which layer?
PLR PLR STE LTE PTESTELTEPTE
STE-STE neighbor discovery
LTE-LTE neighbor discovery
PLR-PLR neighbor discoveryDefinitions
PLR - Physical Layer Regenerator
STE - Section Terminating Equipment
LTE - Line Terminating Equipment
PTE - Path Terminating Equipment
STE-STE neighbor discoveryPLR-PLR neighbor discovery
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Generalized Automatic Discovery
Layer Adjacency Discovery
Who are my neighbor peers?
Physical Media Adjacency Discovery
What is the next box Im physically connected to? Control Entity Logical Adjacency
Establishment
If we are going to participate in a control protocol
who should I talk to? Service Capability Exchange
What kinds of things can your peer box orsubnetwork do? How are you configured?
ITU G.7714 ConceptsData Plane
Data Plane
Control Plane
Control Plane
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Layer Adjacency Discovery
Who is my peer at a particular layer in thetransport system.
Similar to the connectivity supervision
management taskAnswers the question:Am I connected to the
right end point?
Usually continuously monitored General mechanism for this is a trail trace
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Trail Trace in SONET/SDH
FramingA1
FramingA2
TraceJ0
BIP-8B1
OrderwireE1
UserF1
Data ComD1
Data ComD2
Data ComD3
PointerH1
PointerH2
PointerAc tio n
H3
BIP-8B2
AP SK1
AP SK2
Data ComD4
Data ComD5
Data ComD6
Data ComD7
Data ComD8
Data ComD9
Data ComD10
Data ComD11
Data ComD12
SyncS1
REIM0
OrderwireE2
SectionOverhead
LineOverhead
9 rows
90 By tes
Sy nchronous Pay loadEnvelop
Section (regenerator
section) trace J0
Section DCC
Line (multiplex section) DCC
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Trace
J1
BIP-8
B3
label
C2
status
G1
user
F2
multi
frame
H4
Growth
Z3
Growth
Z4
Tandem
N1
Path
Overhead
9 rows
87
Bytes
Synchronous Payload
Envelop Capacity
Trail Trace in SONET/SDH
Path (HO-VC) trace J1
Contains TCM layer
trace and other items
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Trail Trace Summary
Primary usage Detecting miss-connected signals at various layers in
the transport hierarchy. Exists for Path (HO-VC), VT(LO-VC), TCM and Section layers and for most OTNlayers. Conspicuously missing from Line (MultiplexSection) layer.
Operation
Trace text string (16 or 64 characters) is set via amanagement system.
Expected trace (what you should be getting) is also setvia a management system.
Supervision is accomplished by enabling alarms if theexpected trace doesnt match the received trace.
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Current Use of Section Trace Bytes
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J0-Based Neighbor Discovery via EMS
A: TID, AID
Z: TID, AID
EMSReport A, Z Values
Report Z, A Values
Compare
Out-of-band
Control
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Issues
The previous method dumps most of the workback to the EMS
Doesnt necessarily blend with the rest of thecontrol plane
How are the values of the traces filled in? May not work between domains (need some type of
agreement, i.e., a standard!)
Doesnt work for the Line (multiplex section
layer) since no trace The line layer is very important since most ADM and
high capacity cross connects work at this layer.
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ITU-T G.7714.1 Discovery Protocol
Protocol for automatic discovery in SDH andOTN networks
Use of Trail Trace
Specific encoding of trace string with (node, port)
information.Node identification relevant to the control plane
Use of a DCC/GCC
For layers without trail trace a set of messages
exchanged over the data communications channel(DCC) or General Communications Channel (GCC),that are part of the overhead for that layer.
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G.7714.1 Discovery Mechanisms
RS layer:
Within the RS layer, the J0 section trace and Section DCC may be
used to support discovery of the RS TCP-to-TCP adjacency.
MS layer:
Within the MS layer, the Multiplex Section DCC may be used to
support discovery of the MS TCP-to-TCP adjacency.
HOVC layer:
Within the HOVC layer, the higher order Path layer J1 trace may
be used to support discovery of the HOVC TCP-to-TCP adjacency. LOVC layer:
Within the LOVC layer, the lower order Path layer J2 trace may be
used to support discovery of the LOVC TCP-to-TCP adjacency.
SDH Mechanisms from G.7714.1
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G.7714.1 Discovery Mechanisms
OTUk layer:
Within the OTUk layer the SM section monitoring
bytes and the GCC0 may be used to support discovery
of the OTUk adjacency. Specifically, the SAPI subfield
within the SM is used to carry the discovery message.
ODUk layer:
Within the ODUk layer the PM path monitoring bytes
and the GCC-1 and GCC-2 bytes may be used tosupport discovery of the ODUk adjacency. Specifically,
the SAPI subfield within the PM is used to carry the
discovery message.
OTN Mechanisms from G.7714.1
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OTUk Frame Format
From G.709
Use the SAPI (source access point identi f ier) por tion
of the TTI (trail tr ace identi f ier) for G.7714.1
discovery.
TTI BIP-8
BEIBDI
RES
1 2 3 4 5 6 7 8
1 2 3
SM1
2
3
4
1 14 15 3824Row
Column
OTUk OH
3825 4080
OTUk FEC(4 x 256 bytes)
FA: Frame AlignmentFAS: Frame Alignment SignalMFAS: MultiFrame Alignment SignalSM: Section MonitoringGCC: General Communication ChannelRES: Reserved for future international standardisation
1
1 2 3 4 5 6 7 8
FAS
Column #
MFAS SM
9 10 11 12 13 14
RESGCC0
TTI: Trail Trace IdentifierBIP8: Bit Interleaved Parity - level 8BEI: Backward Error Indication
BDI: Backward Defect IndicationIAE: Incoming Alignment ErrorDAPI: Destination Access Point IdentifierSAPI: Source Access Point Identifier
IAE
FA OH
7 8
63
32
0
1516
31
SAPI
DAPI
OperatorSpecific
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ODUk Frame Format
1
2
3
4
1 2 3 4 5 6 7 8
Frame Alignment overhead
Column #
RESOPUk
overhead
OTUk overhead
9 10 11 12 13 14 15 16
Row#
EXP
TCM
ACTTCM5 TCM4
TCM3 TCM2 TCM1
TCM6
GCC1 GCC2
FTFL
PM
RES
1
2
3
4
1 16 17 3824Row
Column
ODUkO
verhead
OPUk Payload(4 x 3808 bytes)
PM: Path Monitoring
TCM: Tandem Connection MonitoringSAPI: Source Access Point Identifier
DAPI: Destination Access Point Identifier
RES: Reserved for future international standardisationACT: Activation/deactivation control channel
BIP8 Parity Block
1514
OPUk
Overhead
APS/PCC
63
TTI BIP-8
32
0
1516
BEIBDI
STAT
1 2 3 4 5 6 7 8
1 2 3
PM and TCMi (i=1..6)
FTFL: Fault Type & Fault Location reporting channel
EXP: ExperimentalGCC: General Communication Channel
APS: Automatic Protection Switching coordination channel
PCC: Protection Communication Control channel
TTI: Trail Trace Identifier
BIP8: Bit Interleaved Parity - level 8BEI: Backward Error Indication
BDI: Backward Defect Indication
STAT: StatusPSI: Payload Structure Identifier
PT: Payload Type
PSI
Mappingspecific
OPUk OH
15 16
1
2
3
4
RES
255
0
1
PT
31
SAPI
DAPI
Operator
Specific
Use the SAPI (source access point identi f ier) por tion of
the TTI (trail trace identi f ier) for G.7714.1 discovery.
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G.7714.1 Information formats
TCP Name Format
In this case a single identifier is used and can beresolved into the node and port ID via a nameserver. Keeps carrier network detailscompletely hidden
DA DCN Address Format
In this case the node ID is the actual address ofthe control entity, known as the discoveryagent, responsible for the discovery process.The port ID is also included.
General ly we need som e type of node and port ident i f ier. However this
inform at ion may be shared in three dif ferent ways:
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G.7714.1 Information formats (cont.)
DA DCN Name Format
In this case which is similar to the DA DCN
Address format, the node name is given and canbe resolved to the DA address via a name
server. This format is useful when longer DCN
addresses such as IPv6 format addresses are
used. The port ID is also included.
General ly we need som e type of node and port ident i f ier. However this
inform at ion may be shared in three dif ferent ways:
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G.7714.1 Discovery Message
Key design objective (accomplished) One generic message format to be used for all different
trail trace and DCC/GCC discovery processes.
Compatibility with existing implementations
Implications Message must fit into the severely space limited J0
section trace message.
Total of 16 bytes. One byte used for CRC, One fordistinguishing character, of remaining 14 bytes we canonly use 7 out of 8 bits (compatibility with ITU-T T.50character set). Additional compatibility requires the useof printable characters!
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G.7714.1 Discovery Message Encoding
14 character slots (7 bit bytes restricted toprintable characters) available
IETF RFC 2045 base64 encoding
Maps 6 binary bits into a single printablecharacter
14 Characters 6*14 = 84 bits available
Octet String (Hex) 0x11 0x23 0x45 0x67 0x8A 0xBC
Binary String 0 0 0 1 0 0 0 1 0 0 1 0 0 0 1 1 0 1 0 0 0 1 0 1 0 1 1 0 0 1 1 1 1 0 0 0 1 0 1 0 1 0 1 1 1 1 0 0
6-bit Decimal 4 18 13 5 25 56 42 60
Mapped Character E S N F Z 4 q 8
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G.7714.1 Discovery Message Formats
0
0 1 2 3 4 5 6 7 8 9
1
0 1 2 3 4 5 6 7 8 9
2
0 1 2 3 4 5 6 7 8 9
3
0 1
0 0 1 0 DA DCN Context ID DA DCN Address
DA DCN Address cont'd Local TCP-ID
Local TCP-ID cont'd
00 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 20 1 2 3 4 5 6 7 8 9 30 1
0 0 1 1 Discovery Agent Name
Discovery Agent Name cont'd Local TCP-ID
Local TCP-ID cont'd
0
0 1 2 3 4 5 6 7 8 9
1
0 1 2 3 4 5 6 7 8 9
2
0 1 2 3 4 5 6 7 8 9
3
0 1
0 0 0 1 TCP Name to look up
TCP-ID Name Message format
DA DCM Address Message format
DA DCM Name Message format
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G.7714.1 procedures
For Trace based mechanism Use the desired message format as the trace string.
For DCC/GCC mechanism
Choose either LAPD or PPP:
LAPD use unnumbered information transfer (UIT)mode to send message.
PPP use PPP LCP extension (RFC1570) packet type 12(identification) with the message as the message!
Discovery Response Message May be sent specifying the node and port that just
received the sent message. How this is done is notcurrently specified in G.7714.1
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OIF UNI 1.0/1.1 Discovery
DCC basedUses either line (multiplex section) or section
(regenerator section) data communications
channel (DCC)
Uses IETF LMP message Format
This usage is not specified in the IETFs Link
Management Protocol (LMP), but is specified
in the UNI1.0/1.1 documents available without
charge at www.oiforum.com
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OIF UNI modified LMP Config
Procedure
Config
Config Ack/Nack
Node ID Message ID Config Objects
Config Message
Hello Interval Hello Dead Interval
Hello Config Object
Node ID: Sending Node ID; CCID: Port number Msg ID: Unique ID assigned
by sending node
Hello Int. : Frequency of Hello messages;
Hello Dead Int.: Waiting time before declaring neighbor dead
Messages sentover each control
channel
CCID
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Verifying Port Connectivity
Node ID =
192.28.134.5
OXC
T
R
T
R
R
T
R
T
Config (Node ID = 192.28.134.2 , CCID = 1)
1
3
4
6
ConfigAck (Node ID = 198.28.134.5, CCID = 4,
Recd. Node ID = 192.28.134.2, Rcv. CC ID = 1)
Node ID =
192.28.134.2
Client
Config (Node ID = 192.28.134.2 , CCID = 3)
ConfigAck (Node ID = 198.28.134.5, CC ID = 6,
Recd. Node ID = 192.28.134.2, Rcv. CC ID = 3)
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Detecting Incorrect Wiring
T T
T
TT
R R
R R
R R
T
1
2
3
10
11
12
N1 (192.14.15.2) N2 (192.15.2.3)
Config (N1, msg=1, ccid=1)
Ack (N2,ccid = 10, msg=2, N1,
rccid=2)
Exchanges at
N1,P1 and N1,P2
Config (N1, msg=2, ccid=2)
Ack (N2,ccid = 11, msg=1, N1,
rccid=1)
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Physical Media Adjacency Discovery
Whos my physical neighbor?
Currently no standards but there has been some goodwork in this area.
Simple Optical Neighbor Discovery (SOND)
Idea: create low speed communications channel at link
turn up for sending/receiving discovery information Uses the Laser Shutdown (LS) signal to transmit
information and the Loss of Signal (LOS) indication toreceive information.
Reference: Stefan N. Larsson, Sten Hubendick, and RobertNedelchef, Wavium AB, Simple optical neighbor discovery(SOND): architecture, applications, and experimentalverification,October 2003, Journal of Optical Networking.
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Control Entity Adjacency Establishment
Concept: separation of control and data plane
Control traffic does not run over the data plane
Link overhead may furnish part of the control planenetwork.
IP Network
IP Network
IPa
IPb
IPc
IPd
LTE or
PXC
LTE or
PXC
Data
Plane
Control
Plane
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Control Entity Adjacency Establishment
How do we find out who our neighbor control entityis? (at a given layer)
Provision this information
Obtain this information via layer adjacency discovery,I.e., the DCN address is the address of the control
entity.
How do we establish and maintain thecommunications channel between these entities?
The IETFs Link Management Protocol (LMP) has
procedures forControl Channel Management In does this via a Configprocedure which verifies
bidirectional connectivity and a heartbeat procedure(namedHello) to monitor connectivity.
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LMP Messages
LMP messages run over UDP (User Datagram Protocol)
Control Channel Management Messages
Link Property Correlation Messages
Link Verification Messages (optional not really needed for
SDH/OTN)
Fault Management Messages (optional not really needed forSDH/OTN)
Version # (Reserved)
LMP Length (Reserved)
Flags Msg Type
Type Message
1 Config
2 ConfigAck
3 ConfigNack
4 Hello
5 BeginVerify
Type Message
6 BeginVerifyAck
7 BeginVerifyNack
8 EndVerify
9 EndVerifyAck
10 Test
Type Message
11 TestStatusSuccess
12 TestStatusFailure
13 TestStatusAck
14 LinkSummary
15 LinkSummaryAck
Type Message
16 LinkSummaryNack
17 ChannelStatus
18 ChannelStatusAck
19 ChannelStatusRequest
20 ChannelStatusRespons
Two flags: Control channel down, and LMP restart
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LMP Objects
LMP Messages consist of LMP Objects ofthe following form
N indicates whether the object is negotiable
C-Type is the generic class type of the objectClass is the particular type of object, e.g., an
IPv4 address versus an IPv6 address
N
C-Type
(object contents)
LengthClass
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LMP Link Management Messages
Config Message (starts the conversation rolling) ::=
ConfigAck Message (used to establish two way connectivity)
::=
ConfigNack Message
::= Hello Message (used as a heartbeat)
::=
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LMP Link Summary Messages
LinkSummary Message ::=
[...]
LinkSummaryAck Message
::=
LinkSummaryNack Message
::=
[...]
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LMP Functions
IP Network
IPa IPb
Control
for A
Control
for B
Conceptual control channelcreated and maintained via LMP
config and hello messages.
Conceptual TE link, a bundle of
real links agreed upon via LMP
summary messages.
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Discovery Summary
Which layer should I discover? Generally rule: all layers that you process.
Most important for layers that you switch at.
What functionality do I want?
Automatic inventory of links
Uni-directional as in G.7714.1
Bi-directional wiring verification
Extra procedure in G.7714.1 may use some LMP messages
Bootstrap G.ASON/GMPLS control plane Bring up control channel
Bundle parallel lines into TE links for representation inrouting protocols.
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Status
InteroperabilityNo significant demonstration of neighbor
discovery interoperability yet
But standardization of G.7714.1 should help.
Deployment
A variety of proprietary implementationstypically tied to link state protocols running
over line or section DCC are being used inproduction transport networks
Integration with existing OSS