Transcript IP Multicast Tutorial

Advanced Topics in Networking:
MPLS and GMPLS
Hang Liu
Thomson Inc., Corporate Research Lab
Princeton, NJ
Note: Thank Dr. Debanjan Saha for the teaching materials on MPLS
MPLS: Multi-protocol Label
Switching
Topics

Introduction



MPLS protocols


History and motivation
MPLS mechanisms
RSVP-TE/CR-LDP
MPLS applications

VPNSs, traffic engineering, restoration
3
WHY MPLS ?

Ultra fast forwarding


IP Traffic Engineering

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Constraint-based routing
Virtual Private Networks


Use switching instead of routing
Controllable tunneling mechanism
Protection and restoration
4
IP Forwarding Table
Dest
47.1
47.2
47.3
Dest
47.1
47.2
47.3
Out
1
2
3
Out
1
2
3
1
47.1.*.*
3
1
Dest
47.1
47.2
47.3
Out
1
2
3
2
3
2
1
47.2.*.*
47.3.*.* 3
2
5
Hop-by-Hop IP Forwarding
Dest
47.1
47.2
47.3
Dest
47.1
47.2
47.3
Out
1
2
3
1 47.1
1
Dest
47.1
47.2
47.3
Out
1
2
3
IP 47.1.1.1
2
IP 47.1.1.1
3
Out
1
2
3
2
IP 47.1.1.1
1
47.2
47.3 3
2
IP 47.1.1.1
6
Routing Lookup
Control CPU
Switch
fabric
I/F
I/F
10 Gbps
10 Gbps
Prefix
9.*.*.*
9.1.*.*
9.2.*.*
9.1.1.*
9.2.1.*
9.1.1.1
9.1.1.2
9.2.1.1
Next Hop
14.1.2.1
67.1.2.2
71.1.2.3
113.1.2.1
113.1.2.1
71.1.2.3
14.1.2.1
71.1.2.3
Interface
2
4
6
8
8
6
2
6
20M packets/sec


Longest prefix match is (was) expensive.
Label matching is much less expensive.
7
MPLS Labels
Intf Label Dest Intf Label
In In
Out Out
3
0.50 47.1 1
0.40
Intf
In
3
Label Dest Intf
In
Out
0.40 47.1 1
1
Request: 47.1
3
Intf Dest Intf Label
In
Out Out
3
47.1 1
0.50
3
2
1
1
47.3 3
47.1
Mapping: 0.40
2
47.2
2
8
Label Switched Path
Intf Label Dest Intf Label
In In
Out Out
3
0.50 47.1 1
0.40
Intf Dest Intf Label
In
Out Out
3
47.1 1
0.50
3
1
47.3 3
Label Dest Intf
In
Out
0.40 47.1 1
IP 47.1.1.1
1 47.1
3
1
Intf
In
3
2
2
47.2
2
IP 47.1.1.1
9
Forwarding Equivalence Classes
LER
LSR
LSR
LER
LSP
IP1
IP2
IP1
IP1
#L1
IP1
#L2
IP1
#L3
IP2
#L1
IP2
#L2
IP2
#L3
IP2
Packets are destined for different address prefixes, but can
be mapped to common path



FEC = “A subset of packets that are all treated the same way by a router”
The concept of FECs provides for a great deal of flexibility and scalability
In conventional routing, a packet is assigned to a FEC at each hop (i.e. L3
look-up), in MPLS it is only done once at the network ingress
10
MPLS Terminology





LDP: Label Distribution Protocol
LSP: Label Switched Path
FEC: Forwarding Equivalence Class
LSR: Label Switching Router
LER: Label Edge Router
11
Label Distribution Methods
Downstream Label Distribution
LSR1
LSR2
Label-FEC Binding
• LSR2 discovers a ‘next hop’ for a particular FEC
• LSR2 generates a label for the FEC and
communicates the binding to LSR1
Downstream-on-Demand Label Distribution
LSR1
LSR2
Request for Binding
Label-FEC Binding
• LSR1 recognizes LSR2 as its next-hop for an FEC
• LSR1 inserts the binding into its forwarding tables
• A request is made to LSR2 for a binding between
the FEC and a label
• If LSR2 is the next hop for the FEC, LSR1 can use
that label knowing that its meaning is understood
• If LSR2 recognizes the FEC and has a next hop for
it, it creates a binding and replies to LSR1
• Both LSRs then have a common understanding
Both methods are supported, even in the same network at the same time
12
Distribution Control
Next Hop
(for FEC)
Incoming
Label
Independent LSP Control
Definition
Comparison
• Each LSR makes independent decision on when to
generate labels and communicate them to upstream
peers
• Communicate label-FEC binding to peers once
next-hop has been recognized
• LSP is formed as incoming and outgoing labels are
spliced together
• Labels can be exchanged with less delay
• Does not depend on availability of egress node
• Granularity may not be consistent across the nodes
at the start
• May require separate loop detection/mitigation
method
Outgoing
Label
Ordered LSP Control
• Label-FEC binding is communicated to peers if:
- LSR is the ‘egress’ LSR to particular FEC
- label binding has been received from
upstream LSR
• LSP formation ‘flows’ from egress to ingress
• Requires more delay before packets can be
forwarded along the LSP
• Depends on availability of egress node
• Mechanism for consistent granularity and freedom
from loops
• Used for explicit routing and multicast
Both methods are supported in the standard and can be fully interoperable
13
Label Retention Methods
Conservative Label Retention
Liberal Label Retention
LSR2
Label Bindings
for LSR4
Label Bindings
for LSR4
LSR1
LSR3
LSR4’s Label
LSR3’s Label
LSR2’s Label
Valid
Next Hop
LSR4
• LSR maintains bindings received from LSRs
other than the valid next hop
• If the next-hop changes, it may begin using
these bindings immediately
• May allow more rapid adaptation to routing
changes
• Requires an LSR to maintain many more
labels
LSR2
LSR1
LSR3
LSR4’s Label
LSR3’s Label
LSR2’s Label
Valid
Next Hop
LSR4
• LSR only maintains bindings received from
valid next hop
• If the next-hop changes, binding must be
requested from new next hop
• Restricts adaptation to changes in routing
• Fewer labels must be maintained by LSR
Label Retention method trades off between label
capacity and speed of adaptation to routing changes
14
Label Encapsulation
L2
ATM
FR
Label VPI VCI
DLCI
Ethernet
PPP
“Shim Label”
“Shim Label” …….
IP | PAYLOAD
MPLS Encapsulation is specified over various media
types. Top labels may use existing format, lower label(s)
use a new “shim” label format.
15
Label Format
Label
20 bits
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

Exp
3 bits
Stack
1 bit
TTL
8 bits
Exp field used to identify the class of service
Stack bit is used identify the last label in the label stack
TTL field is used as a time-to-live counter. Special
processing rules are used to mimic IP TTL semantics.
16
Label Distribution Protocols


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
Label Distribution Protocol (LDP)
Constraint-based Routing LDP (CR-LDP)
Extensions to RSVP
Extensions to BGP
17
LDP:Label Distribution Protocol
Label distribution ensures that adjacent routers have
a common view of FEC <-> label bindings
Routing Table:
Routing Table:
Addr-prefix
47.0.0.0/8
Addr-prefix
47.0.0.0/8
Next Hop
LSR2
Next Hop
LSR3
LSR1
IP Packet
LSR3
LSR2
47.80.55.3
Label Information Base:
Label-In FEC Label-Out
XX
47.0.0.0/8
17
Step 3: LSR inserts label
value into forwarding base
For 47.0.0.0/8
use label ‘17’
Label Information Base:
Label-In FEC Label-Out
17
47.0.0.0/8
XX
Step 2: LSR communicates
binding to adjacent LSR
Step 1: LSR creates binding
between FEC and label value
Common understanding of which FEC the label is referring to!
18
LDP: Basic Characteristics


Provides LSR discovery mechanisms to enable LSR peers to find
each other and establish communication
Defines four classes of messages

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DISCOVERY: deals with finding neighboring LSRs
ADJACENCY: deals with initialization, keep alive, and shutdown of sessions
LABEL ADVERTISEMENT: deals with label binding advertisements, request,
withdrawal, and release
NOTIFICATION: deals with advisory information and signal error
information
Runs over TCP for reliable delivery of messages, except for
discovery, which uses UDP and IP multicast
Designed to be extensible, using messages specified as TLVs
(type, value, length) encoded objects.
19
LDP Messages


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

INITIALIZATION
KEEPALIVE
LABEL MAPPING
LABEL WITHDRAWAL
LABEL RELEASE
LABEL REQUEST
20
Explicitly Routed LSP
Intf Label Dest Intf Label
In In
Out Out
3
0.50 47.1 1
0.40
Intf
In
3
3
Dest
47.1.1
47.1
Intf
Out
2
1
Label
Out
1.33
0.50
3
1
47.3 3
Label Dest Intf
In
Out
0.40 47.1 1
IP 47.1.1.1
1 47.1
3
1
Intf
In
3
2
2
47.2
2
IP 47.1.1.1
21
ER LSP - Advantages

Operator has routing flexibility



policy-based, QoS-based
Can use routes other than shortest path
Can compute routes based on
constraints in exactly the same manner
as ATM based on distributed topology
database.(traffic engineering)
22
ER LSP - discord!





Two signaling options proposed in the
standards: CR-LDP, RSVP extensions:
CR-LDP = LDP + Explicit Route
RSVP ext = Traditional RSVP + Explicit
Route +Scalability Extensions
Market will probably have to resolve it
Survival of the fittest not such a bad thing.
23
MPLS and QoS in IP Network


Integrated Services
Differentiated Services
24
Integrated Services Internet

Applications specify traffic and service specs

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Two classes of service defined

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Tspec: traffic specs including peak rate, maximum packet
size, burst size, and mean rate
Rspec: service spec, specifically service rate
Guaranteed service: satisfies hard guarantees on bandwidth
and delay
Controlled load service: provides service similar to that in
“unloaded network”
RSVP was extended to RSVP-TE support signaling

RSVP was further extend to add MPLS support
25
Differentiated Services Internet

IP packets carry 6-bit service code points (DSCP)


Potentially support 64-different classes of services
Routers map DSCP to per-hop-behavior (PHB)


PHBs can be standard or local
Standard PHBs include




Default: No special treatment or best effort
Expedited forwarding (EF): Low delay and loss
Assured forwarding (AF): Multiple classes, each class with multiple drop
priorities
LSRs don’t sort based on IP headers, hence DSCPs need to be
mapped to EXP field in MPLS shim header



Exp field is only 3-bit wide – can support only 8 DSCPs/PHBs
Labels can be used if more than 8 PHBs need to be supported
Same approach can be used for link layers which do not use Shim
headers, e.g. ATM
26
Traffic Engineering with RSVP
PATH
{Tspec}
PATH
{Tspec}
PATH
{Tspec}
Sender
RESV
{Rspec}
RESV
{Rspec}
RESV
{Rspec}
PATH
{Tspec}
RESV
{Rspec}
Receiver
27
Label Distribution with RSVP-TE
PATH
{Tspec}
PATH
{Tspec}
PATH
{Tspec}
Sender
RESV
{Rspec}
PATH
{Tspec}
RESV
{Rspec}
{Label = 10}
RESV
{Rspec}
{Label = 5}
PATH
{Tspec}
RESV
{Rspec}
28
MPLS Protection


End-to-end protection
Fast node and link reroute
29
MPLS Protection
End-to-end Path Protection
F
Primary LSP
E
A
D
B
C
Backup LSP
Backup and primary LSPs should be route diverse
30
MPLS Protection: Fast Reroute
Detour to avoid CD
Detour to avoid AB
LSR B
LSR A
LSR D
LSR C
Detour to avoid BC

LSR E
Detour to avoid DE
Detour around node or link failures


Detour to avoid link
DE
LSR F
Example LSP shown traverses (A, B, C, D, E, F)
Each detour avoids


Immediate downstream node & link towards it
Except for last detour: only avoids link DE
31
Detour Merging
Detour to avoid AB
Merged detour to
avoid AB and BC
Detour to avoid BC
LSR A


LSR B
LSR C
LSR F
LSR D
LSR E
Reduces state maintained
Improves resource utilization
32
MPLS Protection Types

1+1: Backup LSP established in advance, resources
dedicated, data simultaneously sent on both primary
and backup



Switchover performed only by egress LSR
Fastest, but most resource intensive
1:1 : Same as 1+1 with the difference that data is
not sent on the backup



Requires failure notification to the ingress LSR to start
transmitting on backup
Notification may be send to egress also
Resources in the backup may be used by other traffic

Low priority traffic (e.g., plain IP traffic), shared by other
backup paths
33
MPLS VPN: The Problem
Customer 1
Site 1
Provider Network
10.2/16
Customer 1
Site 2
10.1/16
10.2/16
Customer 2
Site 2
10.1/16
Customer 2
Site 1
10.3/16
Customer 2
Site 3
Customer 1
Site 3
10.3/16
34
MPLS VPN: The Model
Customer 1
Site 1
10.1/16
10.2/16
Customer 1
Virtual Network
10.2/16
10.1/16
Customer 1
Site 2
Customer 2
Site 2
Customer 2
Virtual Network
Customer 2
Site 1
10.3/16
Customer 2
Site 3
Customer 1
Site 3
10.3/16
35
MPLS VPN: The Solution
MPLS LSP
Customer 1
Site 1
10.2/16
Customer 1
Site 2
VRF 1
10.1/16
VRF 1
10.2/16
VRF 2
Customer 2
Site 2
VRF 2
10.1/16
VRF 1
Customer 2
Site 1
VRF 2
MPLS LSP
10.3/16
Customer 2
Site 3
Customer 1
Site 3
10.3/16
36
GMPLS: Generalized MPLS &
ASON: Automatically Switched
Optical Network
Outline

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

ASON Control Plane
Standards
UNI and NNI
Protection and Restoration
38
Traditional Management Plane for Optical Transport Networks
NMS
EMS 2
EMS 3
EMS 1
IP
IP
FR/ATM
FR/ATM
Class 5
Class 5
Optical Transport Network (OTN)
Other
Other



A lot of manual operations
Integration of different EMS and NMS is complex

multiple types of equipment from different vendors with
different technologies
Automatic end-to-end provisioning is not easy

planning, path computation, connection establishment
39
Distributed Control Plane
NMS/EMS
Client Network
(IP, ATM, SDH)
Optical Transport
Network
SPC
Optical
Domain
ENNI
INNI
ENNI
UNI
Optical
Domain
ENNI
Optical
Domain
UNI
SC
signaling and routing over control channel

Distributed control plane offers

automatic neighbor and topology discovery

automatic end-to-end provisioning and connection modification

scalability and interoperability

unified traffic engineering and protection/restoration

In an environment where IP router networks are
interconnected via a mesh optical network
40
ASON Control Plane

Goals of ASON control plane
 Facilitate configuration of connections within an optical
transport network in a reliable, efficient, scalable,
interoperable and automatic way
 Switched connection (SC): requested by a user
 Soft permanent connection (SPC): initiated by the
management plane
 Good for applications required for dynamic circuits
(holding time ~ provisioning time)
 Allow reconfiguring or modifying connections for existing
calls
 Perform protection and restoration function
41
ASON Control Plane Components

Components of ASON control plane


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
Call Controller
Connection Controller
Link Resource Manager
Routing Controller
Discovery Agent
Termination and Adaptation Performer
Etc.
42
Related Standard Bodies

ITU



ASON Architecture and Components
UNI and NNI interfaces
IETF

Generalized GMPLS Protocols

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
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
Extends MPLS/IP protocols based on generalized interface
requirements
signaling (RSVP-TE and CR-LDP with GMPLS extensions)
routing (OSPF-TE and IS-IS with GMPLS extensions)
link management and neighbor discovery (LMP)
OIF


Focuses on application of IETF protocols in an overlay model
Generates implementation agreements
 UNI and NNI
43
GMPLS: Generalized MPLS
PSC
Cloud





LSC
Cloud
FSC Cloud
GMPLS Handles Nodes With Diverse Capabilities.


TDM
Cloud
Packet Switch Capable (PSC)
Time Division Multiplexing Capable (TDM)
Lambda Switch Capable (LSC)
Fiber Switch Capable (FSC)
Each Node Is Treated As an MPLS Label-switching Router (LSR)
Lightpaths/TDM Circuits Are Considered Similar to Label-Switched Paths (LSPs)

Selection of s and OXC ports are considered similar to selection of labels
44
Overview of IETF GMPLS Protocols

GMPLS-based distributed control plane



automatic service provisioning (signaling)
dynamic network topology and resource availability
dissemination (routing)
neighbor discovery and link management (link management)
45
Control Channel

Bi-directional channel is required between two logically or physically
adjacent nodes to exchange control messages

in-band with data (such as two IP routers, SONET overhead bytes)

out-of-band through a separate link or even separate network
(such as an IP network)

de-couple data channel and control channel

one control channel to one or multiple data channels
control channel
data channel 1 (and control channel)
data channel N
Link Bundle
control channel
IP
46
Connection Provisioning through GMPLS
Ingress Node (A)
Request
Egress Node (B)


Connection request received from a client or a management agent at
ingress node
Ingress node computes the explicit route from ingress to egress node

take into account a set of constraints (bandwidth requirements, resource
availability, protection/restoration and traffic engineering constraints)
Require routing protocol to disseminate network topology and link state
information
Signaling the connection establishment along the path



RSVP-TE or CR-LDP extension
47
Signaling Protocol


Establishes and deletes paths

LSP setup: label request and resource reservation/allocation

LSP deletion: label and resource release
GMPLS Signaling


Extends MPLS label semantics to accommodate fiber, waveband, lambda,
TDM and packet-capable LSP establishment
Extends RSVP-TE and CR-LDP for carrying the generalized label objects
over explicit path

Supports bi-directional LSP setup

Suggested Label


Upstream node suggests a label to downstream node for speeding up
configuration
Label Set

Limit the labels what downstream node can choose from
48
Routing Protocol




Disseminates network topology and link resource availability over
control channel (CC)
Manages the link state database and routing tables
 make routing decision
Provides path computation algorithm with the routing information to
obtain explicit route
Traffic engineering (TE) and GMPLS routing extensions
 Extends OSPF or IS-IS
 Support multiple types of GMPLS TE links
 Carry new link attributes
 TE LSA database for explicit path computation
49
Link Bundling
Component Link
Data Channel 1
Data Channel N

Neighboring nodes (e.g. OXCs) connected by multiple parallel links


For standard OSPF, each physical link between a pair of nodes forms a
routing adjacency
 not scale well
To improve routing scalability and reduce the amount of information
handled by routing protocol, in GMPLS routing protocol




Link Bundle
aggregates and abstracts the attributes of the links with similar
characteristics between a pair of nodes
advertises as a single link bundle or Traffic Engineering (TE) link
aggregation leads to information loss
Control channel and data link may be separated
50
Link Management Protocol (LMP)



Multiple fiber links between two adjacent nodes (e.g.
OXC, photonic switches)
Control channels may not use the same physical medium
and interfaces as the data links
Link Management Protocol (LMP)

Provides the capability to manage control channel and data links
between neighboring nodes
51
LMP functionality





Control channel management
 establish and maintain LMP control channel connectivity
between adjacent nodes.
Link property correlation (link bundling management)
 synchronize TE link (link bundle) properties and verify the TE
link properties
 one CC per one or more link bundles
Link connectivity verification
 data link physical connectivity discovery
 mis-configuration and mis-wiring detection
Fault management
 localize and handle data link failure
Service discovery
 automatic discovery of services offered by the network
including signaling protocol type, link and data signal type,
transparency level etc...
52
LMP Different Operation Modes

In-fiber and in-band control channel

one CC per data component link

e.g. using SONET/SDH overhead bytes


control channel management and data link management can be done
together

neighbor discovery

mis-configuration and mis-wiring detection
Out-of-fiber control channel (Ethernet) or in-fiber dedicated channel,



one CC per multiple component links or multiple link bundles
transparent devices that the data is not modified or examined in normal
operation.e.g. photonic switches
test messages are used for data link neighbor discovery and connectivity
verification
53
LMP In-band Control
Node A
Node B
Config (local CID, msg ID, local node ID, config)
ConfigAck (local CID, local node ID, remote CID, msg ID ACK, remote node ID)
Parameter
Negotiation
ConfigNack (local CID, local node ID, remote CID, msg ID ACK, remote node ID, config)
Config (local CID, msg ID, local node ID, config)
ConfigAck (local CID, local node ID, remote CID, msg ID ACK, remote node ID)
Hello (local CID, hello)
Keep-alive
Hello (local CID, hello)
Hello (local CID, hello)
Hello (local CID, hello)



CID: Channel ID
config: HelloInterval and helloDeadInterval
hello: TxSeqNum and RcvSeqNumk
54
LMP Out-Of-Band Control
Control Channel (CC)
Data Channel 1
Test Messages
Data Channel N
Link Bundle
BeginVerify (control channel)
BeginVerifyAck (control channel)
Test (data link)
TestStatusSuccess (control channel)
TestStatusAck (control channel)
.
Test other data component links
.
EndVerifyAck




Most LMP messages are send out-of-band through the control channel
In-band Test messages are sent for link verification and correlation
TE link (link bundle) is disseminated over routing protocol
Routing flooding adjacencies are maintained over control channel and data
forwarding adjacencies (FA) are maintained over component links
55
Unified Control Plane
IP Network
E-NNI
UNI
Optical Network
Optical
subnet
Optical
subnet
IP Network
I-NNI
ATM
ATM
Network
Network
Optical
subnet
E-NNI
E-NNI
ATM
ATM
Network
Network
ATM
ATM
ATM
Network
Network
Network
UNI
IP Network
UNI - User-to-Network Interface
I-NNI - Internal Network-to-Network Interface
E-NNI - External Network-to-Network Interface
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User-to-Network Interface (UNI)
Signaling/Routing
Signaling
LMP
LMP
LMP
UNI
Signaling
OTN
Client
UNI
Client
End-to-end path





UNI supports establishment of connections between the client nodes
over an OTN (overlay model)
Re-use IETF GMPLS protocols

signaling: RSVP-TE, CR-LDP with UNI specific extensions

neighbor and service discovery: LMP with UNI specific extensions
Transport network assigned address (TNA)

an address assigned to a client by the transport service provider

a globally unique address, can be IPv4, IPv6 or NSAP
UNI is used at the edge of the cloud
Inside the cloud - LMP, GMPLS signaling and routing
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UNI Connection Setup Using GMPLS RSVP-TE
Path
ACK
Path
Resv
+ MESSAGE_ID_ACK
ACK
Resv
ResvConf
+ MESSAGE_ID_ACK
UNI Transport Connection Established
Source UNI-C may start transmitting
ACK
ResvConf
Destination UNI-C may start transmitting
ACK
Source UNI-C
Ingress UNI-N
Egress UNI-N
Destination UNI-C
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Network-to-Network Interface
Routing
Routing
OTN1
OTN1
ENNI
UNI
OTN1
ENNI
UNI
Client
Client
Signaling
Signaling
Signaling
End-to-end path

Inter-domain signaling: extends GMPLS signaling protocol, e.g. RSVP

Inter-domain routing

extends GMPLS IGP routing protocols: e.g. multi-area OSPF, IS-IS

extends inter-domain routing protocol (BGP) to exchange topology
information across domain boundaries


abstraction and summarization of intra-domain routing information
Neighbor discovery and link management: LMP
59
Path Protection and Restoration in OTN
primary
A
C
B
protection
D
F


E
protection
primary
G
H
Dedicated 1+1 Protection

Primary and protection path diversified

During normal operation mode, both paths are completely provisioned, carry the
optical data traffic and the egress elects the best copy of the two

Primary and protection path provisioning through GMPLS signaling protocols, e.g.
RSVP
No delay but not efficient in terms of netwok resource utilization
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Shared Mesh Protection and Restoration
primary
A
D
F


C
B
Shared restoration channel
primary
G
E
H
Shared mesh restoration path is pre-computed and pre-provisioned

Resource is reserved on the links but no cross-connects are created along the
restoration path

The complete establishment of the restoration path occurs only after the primary
path fails

The common restoration resource reserved on a link may be shared by multiple
restoration paths to restore multiple primary paths
 In order to avoid contention during a single node failure, two restoration paths
may share the common reserved restoration resource only if their respective
working paths are mutually node disjoint.

The bandwidth reserved for restoration on a link can be smaller than the total
bandwidth required by all the working paths recovered by it

the resource reserved for restoration can also be used for low priority pre-emptible
traffic in normal operating mode
Efficient but with a delay
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GMPLS Control Plane Prototype
GMPLS
Management
GUI/CLI
GUI/CLI
Agent
GMPLS Application
GMPLS Controller
GMPLS Interface Adapter
Optical Switch
Routing
Routing
Table
Manager
Path
Computation
Signaling
RSVP-TE
GMPLS
Database
Link Bundle Table
Port Table
Path Table
Switch Control
LinkIPC
Management
OSPF-TE
Data Plane
Control
LSA DB
Layer 3 (IP)
Layer 2 (Ethernet)
Layer 2 (SONET)
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