International Telecommunication Union
ITU-T
Routing in Multi-Layer
Transport Networks
Jonathan Sadler
Office of the CTO – Technology Strategy, Tellabs
Chair, OIF Architecture & Signaling Working Group
SG15 Special Representative to IETF for Routing
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
Agenda
ITU-T
o Service-based routing
o ASON Multi-layer Routing Architecture
o Remote Path Computation
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
2
Discussion of Convergence is Everywhere
ITU-T
o “…the access infrastructure telcos are building to support IPTV
services will finally give them the ability to converge voice,
video and data onto a single network…”
– Americas Network
o Pseudo-Wires are “the solution for convergence in future
telecom networks, because it preserves profitable legacy
services even as it enables the creation of a truly nextgeneration network” – Heavy Reading
o “3GPP defines a new subsystem to enable the convergence of
voice and data applications and the harmonization of various
mobile network technologies over IP”
– Deutsche Bank
Convergence is changing
the face of the network
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
3
The Benefits of Convergence
ITU-T
o Services reduced to applications on converged
infrastructure
• Reduced operations
• Reduced core cap-ex
o New services can be provided
• Individual Networks per Service limited service interaction
o Packet & optical routing convergence can improve network
performance even if only IP services are provided
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
4
The Reality of Convergence
ITU-T
o Non-native service delivery
• End User Services are always layered on something else
o The whole network will not be converged overnight
• Too many existing services already deployed
o The whole network will never be completely converged
• Fully depreciated equipment still generates revenue
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
5
How Can This Be Accommodated?
ITU-T
o Common flexible control method that understands layering
• Path Computation that understand layered networks
—Provides service routing given view of potential/available
server layer resources
• Signaling mechanisms that coordinate calls in different layers
• OSSes that can handle integrated views of layer networks
—Relate services requests (client layer calls) to server
resources in use
• Definitions for server layer resources other than SONET/SDH
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
6
Access A
The Network is
Segmented
ITU-T
CPE-A
Core
CPE-B
Access B
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
7
Access A
ITU-T
CPE-A
Different
Organizations
Manage Different
Parts of the
Network
Core
CPE-B
Access B
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
8
We will fill
your order
within 3
months
Access A
ITU-T
Provisioning
Service is
expensive and
time consuming
CPE-A
Core
CPE-B
Access B
I forgot that
we ordered
this service!
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
9
Sure, we’re
setting your
service up as
we speak
Access A
Control Plane
Speeds it up
ITU-T
CPE-A
Core
CPE-B
Access B
Wow, that
was fast!
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
10
Access A
(Ethernet)
ITU-T
Will use of different
technologies cause
the problem to
reoccur?
CPE-A
Core
(MPLS Pseudo Wire)
CPE-B
Access B
(SONET/SDH)
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
11
It doesn’t have to…
ITU-T
Access A
(Ethernet)
OCN
UNI
Ethernet Network
GE/NNI
T1, T3, OCN
UNI
GE/NNI
OCN
UNI
GE/NNI
GE/NNI
CPE-A
T1, T3, OCN
UNI
10/100
BPON
BPON
OCN/NNI
BPON
GE/UNI
Core
(MPLS Pseudo Wire)
10/100
GE/MPLS
CPE-B
nxT1
GE/UNI
OCN/NNI
nxT1
10/100
MPLS Network*
Access B
(SONET/SDH)
OCN/NNI
10/100
T1, T3, OCN
UNI or Null
T1, T3, OCN
UNI or Null
OCN/NNI
OCN/NNI
OCN/NNI
STS1 Network*
OCN/NNI
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
12
Sure, we’re
setting your
service up as
we speak
ITU-T
OCN
UNI
Ethernet Network
GE/NNI
T1, T3, OCN
UNI
GE/NNI
OCN
UNI
GE/NNI
GE/NNI
T1, T3, OCN
UNI
10/100
BPON
BPON
OCN/NNI
BPON
GE/UNI
10/100
End-to-end Signaled
Service Provisioning!
GE/MPLS
MPLS Network*
10/100
GE/UNI
nxT1
OCN/NNI
OCN/NNI
nxT1
10/100
T1, T3, OCN
UNI or Null
T1, T3, OCN
UNI or Null
OCN/NNI
OCN/NNI
Wow, that
was fast!
OCN/NNI
STS1 Network*
OCN/NNI
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
13
International Telecommunication Union
ITU-T
ASON Multi-layer Routing
Architecture
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
Multi-layer overview
ITU-T
o Need path computation for a network made up of many
different technologies, in any layer that has switching
flexibility.
o Current methods separate network topologies per
technology, creating separate discontinuous graphs
o Path Computation methods only operate on graphs without
discontinuity.
Need to make a continuous routing
view for a multi-technology network
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
15
Representation of Server Layer connectivity
ITU-T
o G.8080 (2006): Two major approaches, with two minor forms:
• Server Layer Representation using Links only:
— Client layer links resulting from established server layer trails
o Result of cross connection of fibers, HOVC paths, etc.
— Client layer links provided by potential server layer trails
o Abstract links representing potential connectivity
o Requires management specification
• Server Layer Representation using Links & Subnetworks
— Client layer abstract node containing server layer
o Abstract topology representing potential connectivity
o Can be generated automatically
— Server layer topology shadow in client layer
o Non-abstract topology showing server links incl. attributes
o Can be generated automatically
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
16
Representation using client links (actual)
ITU-T
o Connection is established in Server Layer
o Link appears in Client Layer
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
17
Representation using client links (potential)
ITU-T
o Link is put into client layer knowing that server layer
resources exist
o Server layer trail is established when link is put into use
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
18
Representation using client subnetwork
ITU-T
o Client layer is provided with an abstract node that represents
the server layer connectivity
• Routing can compute a path in the client layer
o Server layer connection established when abstract node
appears in client
layer ERO
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
19
Representation using client subnet & links
ITU-T
o Client layer contains server layer topology
o Routing can see all attributes of server layer resources
o Server layer connection established using client layer ERO
information
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
20
What information is required?
ITU-T
o Understanding of adaptations in use
G.805
o Understanding of termination/switching capability
o Ability to control choice of server layer trails in
place of client layer links
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
Policy
21
What information is required?
ITU-T
o GMPLS Routing Announcements
• Limited to switching capability information
• Need to add adaptation and termination capability info
o Adding this information creates a “backward
compatibility” problem
• Similar to problem that exists between MPLS and GMPLS
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
22
International Telecommunication Union
ITU-T
ASON Support for
Remote Path Computation
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
What is PCE?
ITU-T
o PCE = Path Computation Element
o Facilitated by ASON Functional Architecture
• Functional Architecture makes no assumptions on
physical location
o Essentially a remote procedure call method
• Used within an area between Signaling (CC) and
Routing instances (RC)
• Used between areas by routing instances (RC)
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
24
Use of PCE in
What
single
is technology
PCE?
areas
ITU-T
o Enables end-to-end path computation without knowing the
whole network topology
• Source specified constraints are communicated
• Path Computation performed on nodes with access to
topology
• Provides support for inspecting interior of abstract nodes
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
25
Example of PCE interaction
ITU-T
D
C
RCA0
RCA0
Connection
Request
H
RCA0
3
8
1
36
4
A
5
B
RCA1
2
RCA1
F
RCA1
G
RCA3
RCA3
CC
CC
I
RCA3
RCA3
9
6
12
35
CC
11
10
LRM
15
34
CC
14
13
LRM
24
31
7
CC
17
16
18
33
23
LRM
LRM
22
LRM
27
30
CC
26
25
CC
28
29
LRM
LRM
21
32
A0
E
D
RCA2
RCA2
B
CC
A
CC
H
C
L2
L3
L1
E
I
F
L4
G
G
L5
L6
A3
20
19
A1
A2
LRM
LRM
Subnetwork
Routing Area
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
Equipment Node
RC-RC Route
Query
26
Use of PCE in mixed-technology areas
ITU-T
o If all nodes to support multi-layer control plane, need for
PCE is limited to path computation for special constraints
• Many network requests can be handled through ASON Source
Routing methods
o Nodes that don’t support multi-layer control plane can PCE
to make up for inability to support new routing attributes
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
27
Example of multi-technology PCE interaction
ITU-T
D
C
RCA0
RCA0
Connection
Request
H
RCA0
3
8
1
36
4
A
5
B
RCA1
2
RCA1
F
RCA1
G
RCA3
RCA3
CC
CC
I
RCA3
RCA3
9
6
12
35
CC
11
10
LRM
15
34
CC
14
13
LRM
24
31
7
CC
17
16
18
33
23
LRM
LRM
22
LRM
27
30
CC
26
25
CC
28
29
LRM
WDM
LRM
SDH
21
32
SDH
A0
E
D
RCA2
RCA2
B
CC
A
CC
H
C
L2
L3
L1
E
I
F
L4
G
G
L5
L6
A3
20
19
A1
A2
LRM
LRM
Subnetwork
Routing Area
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
Equipment Node
RC-RC Route
Query
28
Conclusion
ITU-T
o Network continues to strive for convergence
• Convergence technology chosen will be based on services
offered, causing different technologies to be used
• Network will not be converged overnight
o New mechanisms defined in G.8080 to represent
multi-layer networks allowing for path computation.
o Path Computation Elements provide a method for
backward compatibility between single-layer and multilayer capable nodes.
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
29