mpls day 1 - introduction to mpls
Post on 07-Aug-2018
260 Views
Preview:
TRANSCRIPT
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
1/42
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
2/42
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
APRICOT 2014 MPLS WORKSHOPINTRODUCTION TO MPLS
Speaker NameDate
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
3/42
3
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
AGENDA
1. Introduction to MPLS
2. MPLS Terminology
3. Fundamentals of MPLS
4. Label Distribution Protocol (LDP)
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
4/42
4
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
INTRODUCTION TO MPLS
MPLS IS A LABEL SWITCHING TECHNOLOGY THAT COMBINES THE TRAFFIC ENGINECAPABIL IT IES OF ATM WITH THE FLEXIB IL ITY AND SCALABIL ITY OF IP
MPLS PROVIDES THE AB IL ITY TO ESTABL ISH CONNECTION-ORIENTED PATHS OVERCONNECTIONLESS IP NETWORK, AND FACIL ITATES A MECHANISM TO ENGINEER NTRAFFIC PATTERNS INDEPENDENTLY OF SHORTEST PATH ROUTING TABLES
MPLS TECHNOLOGY OFFERS MANY SERVICES , INCLUDING LAYER 2 AND LAYER 3 VTRAFFIC ENGINEERING, AND RES IL IENCY
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
5/42
5
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MULTI PROTOCOL LABEL SWITCHINGINTRODUCTION
RFC 3031 describes the Multiprotocol Label Switching (MPLS) architecture
The term Multiprotocol indicates that an MPLS architecture can transport paylmany different protocols (IPv4, IPv6, Ethernet, ATM, Frame Relay, etc.)
Label Switching describes that an MPLS domain switches, rather than routes, p
Service Provider Core
MPLS routers forward packets using pre-determined labels
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
6/42
6
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLSIMPROVING PACKET FORWARDING PERFORMANCE
Label switching was initially considered an improvement over IP packet routing a
simpler lookup
- 20-bit fixed label size versus 32/128-bit longest match IP destination lookup
Advances in network processors lead to MPLS for Layer 3 packet forwarding perfo
an obsolete use-case
IP SOURCE
IP DESTINATION
OPTIONS
PAYLOAD
IP SOURCE
IP DESTINATION
OPTIONS
PAYLOAD
MPLS LABEL
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
7/42
7
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLSIP ROUTING REVIEW
IP routing follows a simple process at each router:
1. Check and remove the L2 encapsulation header of the incoming packet
2. Examine the L3 (IP) header and perform a longest match lookup on the destination IP a
forwarding table
3. Determine the next-hop interface
4. Build a new L2 encapsulation header and forward the packet to the next-hop router, de
IP TTL/hop count
IP
L2
IP
L2
IP
L2
Longest match lookup ondestination address
Prefix Next-hop Metric
10.1.1.0/24 R5 50
10.1.1.0/24 R6 20
10.1.0.0/16 R7 10
R1 R2 R3 R4 R6
R5
R7
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
8/42
8
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLSLIMITATIONS OF IP FORWARDING PARADIGM
Destination based routing lookup only
- No ability to look at the source address of packets without complicated configuration such as
next-hop- No ability to steer different types of traffic over different next-hops without PBR
IP over underlay technologies (e.g. ATM)
- Was used extensively in the past to abstract the L2 and L3 topologies of networks by using undsuch as ATM or Frame Relay to build any-to-any paths in large networks
- This approach could build a pseudo-full-mesh in a large scale network to optimize traffic flow
- Has been repeated in the MPLS world with IP-over-MPLS overlays
- Early form of IP TE
Traffic Engineering limitations- In many networks it is desirable to send different traffic types via different paths (e.g. lowest
bandwidth, etc)
- This sort of TE is difficult to represent in IP routing without complicated PBR configurations
- MPLS-TE allows for this information to be reflected in the network, and to map traffic to diffeselected by the source node
- In many networks, not all links were utilized to get traffic across networks, leading to congestand under-utilization on others
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
9/42
9
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLSHOW IT HELPS
MPLS is a label based forwarding paradigm
- Separating IP destination from the forwarding lookup
Labels usually correspond to IP destination networks
- Similar to traditional IP routing
- Labels can also correspond to other parameters such as service IDs for pseudowire service
parameters, traffic engineering tunnel, etc
Separating packet forwarding from destination lookup gives operators flexibility t
the problems discussed on the previous slide
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
10/42
10
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLSHOW IT HELPS DESTINATION BASED FORWARDING LOOKUP
MPLS changes the forwarding paradigm by using labels and switching between thecenter of the network
Only edge routers need to be IP aware, core routers are label-aware
Label tables contain ingress label, egress label, next-hop, and action information
swap)
Label based lookup
FEC In-Label Out-label Next-Hop
X 1000 2000 R2
Y 1234 4567 R2
R1 R2 R3 R4
IP
L2
1000
IP
L2
2000
IP
L2
3000
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
11/42
11
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLSHOW IT HELPS TRAFFIC ENGINEERING
MPLS gives operators flexibility for traffic engineering (TE) in their networks, incability to use multiple links
Typically, IP will pick the best path (commonly, lowest metric). In topologies suc
here, ECMP is not possible to implement due to multiple links and metrics
MPLS-TE can force traffic at the ingress node (R1) to pick specific links, or share
multiple paths
R1
R2 R3
R4
R5 R6
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
12/42
12
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLSHOW IT HELPS TRAFFIC ENGINEERING
In a complex topology, sometimes bandwidth is a key driver
- It might be required to use a higher-bandwidth, but less-metric-preferred path, to carry
across the network
Sometimes latency is a key driver
- Low-latency paths might be preferred for voice traffic
Put other traffic on remaining path(s)
R1
R2 R3
R4
R5 R6
1G
1G
10G
10G
10G
1G
1G
1G
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
13/42
13
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLSHOW IT HELPS
Service flexibility and convergence
- Since MPLS matured and the primary goal of IP performance improvements became less r
has been optimised for service flexibility and delivery
- Delivering Layer 2 services such as point-to-point pseudowires or multipoint services like
- Delivering Layer 3 services such as L3VPNs (aka VRF, VPRN, IP-VPN, RFC2547bis, RFC4364
- This allows a single IP core to provide many service types across the network optimizing
for service providers
Network resiliency
-As part of signalling paths through an IP network, MPLS can signal for backup / alternate both the originating router and mid-point routers perform protection of paths should a lin
- Typically this is seen as IP networks competing with traditional optical protection mecha
DWDM platforms
BGP free core operations
- As traffic can be tunneled across the core nodes, BGP can be removed from these nodes
BGP/L3 only to exist on the IP edge
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
14/42
14
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLS TERMINOLOGY
MPLS Terminology
- iLER: Ingress Label Edge Router
- eLER: Egress Label Edge Router
- LSR: Label Switch Router
- LSP: Label Switched Path
- FEC: Forwarding Equivalence Class
Service Provider Terminology
- CE: Customer Edge router
- PE: Provider Edge router
- P: Provider (Core) Router
CE PE P P PE
iLER eLER
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
15/42
15
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLS TERMINOLOGYLABEL SWITCHED PATHS
Labels are pushedonto packets when they enter the service provider network
Labels are swappedacross the network as they transit a core/transit router
Labels are poppedwhen they reach the egress edge of the network
LSPs refer to the end-to-end unidirectional tunnel across the network, regardleslabels it consists of
LSP is a logical entity that reflects the connection between routers
CE PE P P PE
PACKET
PACKET
LABEL 1
LabelPush
PACKET
LABEL 2
LabelSwap
LabelSwap
PACKET
LABEL 3 PACKET
LabelPop
LSP
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
16/42
16
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLS TERMINOLOGYFORWARDING EQUIVALENCE CLASS
The Forwarding Equivalence Class (FEC) refers to packets that are forwarded in t
manner over the same path with the same forwarding treatement
In IP-only networks, FECs usually correspond to an IP prefix in the routing table
- 10.1.1.0/24 with next-hop 192.0.2.1
- Packets destined for 10.1.1.1 and 10.1.1.2 will both be forwarded to 192.0.2.1; meaning
same FEC
- IP-only FEC lookups are performed at each hop
In MPLS networks, FECs can be defined based on destination IP prefixes and othe
criteria
- MPLS based FEC lookups are performed onlyat the ingress LER on incoming packets
- The FEC lookup determines the next-hop LSR and the label to be pushed onto the packet
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
17/42
17
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLS TERMINOLOGYFORWARDING EQUIVALENCE CLASS
FEC lookup is performed at the ingress LER (R1 in this example), and the label is on the FEC lookup
LSRs R2 and R3 perform label swap operations
FEC lookup
FEC In-Label Out-label Next-Hop
X 1000 2000 R2
Y 1234 4567 R2
R1 R2 R3 R4
IP
L2
1000
IP
L2
2000
IP
L2
3000
Label swap
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
18/42
18
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLS TERMINOLOGYPLANES
The Control Plane in a router refers to the proc
control protocols, such as routing information a
-OSPF, IS-IS, LDP, BGP are control plane processes
The Routing Information Base (RIB) receives all
information from routing protocols, and comput
path information for the Forwarding Informatio
MPLS protocols exchange label bindings for thei
build the Label Information Base (LIB), which is
the LFIB
The FIB is a data plane (or forwarding plane) fu
refers to how the line cards will actually forwar
Control Plane
Data Plane
RIB OSPF
BGP IS-IS
FIB
LIB
LFIB
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
19/42
19
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLS ARCHITECTUREMPLS LABELS
MPLS labels use a 32-bit field thats inserted between the L2 and L3 headers, oft
as a shim header
-Known as frame mode
Header format:
- 20 bit Label
- 3 bit Traffic Class field (aka EXPerimental, or Class of Service)
- 1 bit Bottom of Stack field
- 8 bit Time To Live (TTL) field
Label TC S TTL
3 bits 120 bits 8 bits
Ethernet
MAC
MPLSShim
(0x8847 or0x8848)
Packet
Payload
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
20/42
20
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLS ARCHITECTURESPECIAL LABEL VALUES
Some special MPLS label values have been reserved:
- 0: IPv4 Explicit Null
-1: Router Alert
- 2: IPv6 Explicit Null
- 3: Implicit Null
- Used for Penultimate Hop Popping (PHP)
- 7: Entropy Label Indicator (ELI)
- 13: GAL Label
-14: OAM Alert Label
Reserved labels are documented by IANA:
- http://www.iana.org/assignments/mpls-label-values/mpls-label-values.xhtml
http://www.iana.org/assignments/mpls-label-values/mpls-label-values.xhtmlhttp://www.iana.org/assignments/mpls-label-values/mpls-label-values.xhtmlhttp://www.iana.org/assignments/mpls-label-values/mpls-label-values.xhtmlhttp://www.iana.org/assignments/mpls-label-values/mpls-label-values.xhtmlhttp://www.iana.org/assignments/mpls-label-values/mpls-label-values.xhtmlhttp://www.iana.org/assignments/mpls-label-values/mpls-label-values.xhtmlhttp://www.iana.org/assignments/mpls-label-values/mpls-label-values.xhtmlhttp://www.iana.org/assignments/mpls-label-values/mpls-label-values.xhtmlhttp://www.iana.org/assignments/mpls-label-values/mpls-label-values.xhtmlhttp://www.iana.org/assignments/mpls-label-values/mpls-label-values.xhtml -
8/21/2019 Mpls Day 1 - Introduction to Mpls
21/42
21
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLS ARCHITECTUREMPLS LABEL STACK
MPLS allows multiple labels to be inserted to a packet, referred to as stacking
These labels are typically used to provide different functions in the network
- A service labelmight identify a customer specific VPN
- A transport labelmight identify the LSP between two routers
- Other labels might be added depending on network complexity and topology, such as Fas
Label stacks impact your MTU, as each time one
label is added the packet size grows by 32 bits
-
Its not unusual to have 5-6 labels in a packet in thecore of a network
- Check your routing platforms for limitations around
pushing/popping labels
- Ensure your MTU is engineered correctly!
The bottom label has the S bit set to 1
- Indicating bottom of stack
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
22/42
22
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLSLABEL ASSIGNMENT AND DISTRIBUTION
Labels are locally significant
- Meaning that they are only relevant to an LSR
LSR assigns labels to prefixes learnt in the routing table
Label bindings are exchanged by adjacent LSRs
-
When LSRs are exchanging label binding information, two approaches can be take
- Unsolicited modewhere the downstream LSR advertises label bindings to all adjacent LS
whether the adjacent LSR demands the label or not (MP-iBGP, LDP)- On-demand mode where the downstream LSR advertises label bindings to adjacent LSRs
the label binding (RSVP-TE)
MPLS
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
23/42
23
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLSCOMPARISON OF UNSOLICITED AND ON-DEMAND
Unsolicited mode: Downstream-on-demand mode:
FEC In-Label Out-label Next-Hop
R1
10.1.2.0/24 - 20 R2
10.1.3.0/24 - 40 R2
R2
10.1.2.0/24 20 - Loopback
10.1.3.0/24 40 30 R3
R3
10.1.3.0/24 30 - Loopback
30|10.1.3.0/2420|10.1.2.0/24
40|10.1.3.0/24
Request labelfor 10.1.3.0/24
30|10.1.3.0/24
FEC In-Label Out-label Next-Hop
R1
10.1.3.0/24 - 40 R2
R2
10.1.2.0/24 20 - Loopback
10.1.3.0/24 40 30 R3
R3
10.1.3.0/24 30 - Loopback
MPLS
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
24/42
24
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLSCONTROL MODES
Ordered Control
- LSRs will advertise FECs upstream only when downstream routers have advertised a label
Independent Control
- LSRs will advertise FECs upstream regardless of whether a downstream router has advert
--|10.1.3.0/24
I know where10.1.3.0/24 is, butI will not advertise
it yet
--|10
I know where10.1.3.0/24 is and Iwill advertise it
now!
MPLS
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
25/42
25
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLSLABEL RETENTION MODES
LSRs maintain received label bindings through two approaches
Conservative Retention mode
- A router that does not need a specific label binding will not hold the binding
Liberal Retention mode
- A router that does not need a specific label binding willhold the binding
30|10.1.3.0/24
I dont need thebinding for10.1.3.0/24 now, I
will delete it
I dont need thebinding for10.1.3.0/24 now, I
but I will keep it
MPLS
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
26/42
26
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLSPENULTIMATE HOP POPPING
Penultimate Hop Popping (PHP) is when the label at the top of the stack is poppe
upstream LSR of the egress LER
The egress LER requests the popping through the label distribution protocol
- Egress LER advertises the implicit-nulllabel
This saves a lookup in the egress LER, optimizing performance
MPLS
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
27/42
27
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLSIMPLICIT AND EXPLICIT NULLS
When a downstream router advertises a FEC with the Implicit Null label, it is req
upstream router perform Penultimate Hop Popping
-This removes the transport tunnel MPLS header and leaves the router with only the paylotunnel header), and can result in a loss of QoS information as the MPLS Transport Class fi
present
- Note: Implicit Null label is a signaling-only label, and not visible in the forwarding plane
A downstream router may also advertise a FEC with the Explicit Null label, which
used for PHP
-The upstream LSR will send the packet to the LER with the Explicit Null label set, which Transport Class field
- The LER will not use the MPLS header for anything other than the QoS information
- Thus, the Explicit Null header is visible in the forwarding plane
MPLS
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
28/42
28
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLSTRANSPORT TUNNEL SIGNALING PROTOCOLS
Label Distribution Protocol (LDP)
Defined in RFC5036
IGP-based tunnels only
Simple configuration
Automatic tunnel creation
No Traffic Engineering support
IGP dependant convergence time
Also called Link or Interface LDP
Downstream Unsolicited mode
Liberal retention
Resource Reservation ProtocoEngineering (RSVP-
Defined in RFC3209
Fully customizable tunnel paths
Ability to run more complex pa
with administrative constraints
Decoupled from IGP
Traffic protection mechanisms
Higher administrative overhead
Downstream on Demand mode
Conservative retention
MPLS
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
29/42
29
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLSSERVICE TUNNEL SIGNALING PROTOCOLS
Targeted LDP (T-LDP)
Defined in RFC4447
Used for L2VPNs
Creates an end-to-end session between two PE
routers
Not to be confused with LDP
Multi-Protocol Border GatewayBGP)
Based on RFC4364 and many ex
Used for L3VPN services, L2VPN
many extensions
Multi-Protocol due to its suppor
address families in addition to
MPLS
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
30/42
30
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLSLABEL DISTRIBUTION PROTOCOL (LDP) INTRODUCTION
RFC 3036, later updated by RFC 5036, defines LDP as a label distribution protoco
Routers configured for LDP establish an LDP session between them and become p
The LDP sessions enable the exchange of label/FEC binding (mapping) informatio
LDP operates in two distinct modes:
- Link (or interface) LDP - Establishing Transport Tunnels
- Targeted LDP - Establishing Service Tunnels between PE routers
LDP is a TLV based messaging protocol
MPLS
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
31/42
31
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
Service Tunnel 1
Service Tunnel 2
MPLSLDP: TRANSPORT AND SERVICE TUNNELS
Link LDP is used to establish transport tunnels
-iLER uses the transport tunnel to reach the eLER
Targeted LDP is used to establish L2VPN service tunnels
- eLER uses the service tunnel for service de-multiplexing
Transport Tunnel
Service 1
Service 2
Service 1
Service 2
MPLS
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
32/42
32
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLSLDP: LINK LDP
Link LDP sessions are established between all directly adjacent LDP routers
Routers exchange label bindings with each other over LDP sessions
This creates a full-mesh of transport tunnels in the network
LDP relies on IGP for operation and convergence
MPLS
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
33/42
33
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLSLDP: LINK LDP OPERATION OVERVIEW
The following four processes create and maintain a Link LDP session:
- Peer Discovery Routers use LDP Hello messages to automatically discover other LDP pe
-Session Establishment and Management LDP sessions are built between LDP peering rouare maintained via keepalive messages
- Label Management After sessions are established, LDP distributes label bindings, and w
necessary
- Notification LDP uses notification messages to alert LDP peering routers about errors
LDP uses both UDP and TCP for transport services
-UDP based messages (port 646)- Discovery messages periodically announce and maintain an LDP router in a network
- TCP based messages (port 646)
- Session messages establish, maintain, and terminate sessions between LDP peers
- Advertisement messages create, change, and delete label mappings for FECs
- Notification messages signal errors and other events
MPLS
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
34/42
34
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLSLDP: PDU STRUCTURE
LDP ID ( 4 bytes LSR ID + 2 bytes label space)
PDU Length ( 26 )Version ( 1 )
Message ID
Message Length ( 16 )Message Type ( 0x4001)U
U Length ( 8 )FEC TLV ( 0x100 )F
Prefix ( 100.0.0.2 )
FEC Element Length ( 32 )FEC Element Address Type ( ipv4 == 1 )FEC Type ( prefix FEC == 2 )
MPLS
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
35/42
35
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLSLDP: PEER DISCOVERY PROCESS (HELLO)
MPLS
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
36/42
36
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
MPLSLDP: HELLO PARAMETERS
LDP-ID (LDP Identifier): 6-byte field that identifies an LSR uniquely along with its
Used in all the LDP messages
-The LSR ID is typically a loopback/system address
- The Label Space ID identify label space within the LSR. For platform-wide label spaces, i
zero
Transport Address: A necessary parameter to establish the subsequent LDP sessio
neighbor
Hello Timeout: Routers continue exchanging LDP Hellos after a successful discove
is declared down if no hello messages are received from that neighbor within the
LSR ID
(32-bit router ID)
Label Space ID
(16 bits)
MPLS
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
37/42
37
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
LDP: LDP SESSION ESTABLISHMENT
MPLS
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
38/42
38
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
LDP: MESSAGE TYPES
TYPE NAME FUNCTION
0x0001 Notification Signals errors and other events
0x0100 Hello Announces the presence of an LSR
0x0200 Initialization Starts the session establishment process
0x0201 KeepAlive Monitors the integrity of the LDP session transport connection
0x0300 Address Advertises the interface addresses to an LDP peer
0x0301 Address Withdraw Withdraws a previously advertised interface address
0x0400 Label Mapping Advertises a FEC-label binding to an LDP peer
0x0401 Label Request Requests a FEC-label binding from an LDP peer
0x0402 Label Withdraw Requests the peer remove from its LIB a previously signaled labe
0x0403 Label Release Signals the peer the LSR no longer needs specific FEC-label mapprequested of and/or advertised by the peer
0x404 Label Abort Request Aborts an outstanding Label Request message
0x3E00 0x3EFF Vendor Private Conveys vendor-private information between LSRs
0x3F00 0x3FF Experimental LDP experimental extensionsundefined use
MPLS
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
39/42
39
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
LDP: LABEL ADVERTISEMENT
Link LDP sessions are established between all adjacent routers
Label bindings are generated for Loopback/System Ips R6 generates a label binding and advertises it for 203.0.113.0/24
- This is advertised (flooded) throughout the network (Downstream Unsolicited mode)
- Routers may receive the advertisement multiple times in a highly meshed network
203.0.113.0/24
Version =
LDP-Id =
Message-TMapping
FEC = 203
Label = 1
MPLS
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
40/42
40
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
LDP: TARGETED LDP
Used to exchange service labels for Layer 2 Services (VLL, VPLS)
Used independently from its Link LDP counterpart
Peers do not have to be directly connected (typically established between 2 PE ro
have services configured)
Also used in LDP over RSVP environments
T-LDP
MPLS
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
41/42
41
COPYRIGHT 2013 ALCATEL-LUCENT. ALL RIGHTS RESERVED.
LDP: TARGETED LDP OPERATION
Operation is very similar to Link LDP
T-LDP sends hellos via Unicast
-
8/21/2019 Mpls Day 1 - Introduction to Mpls
42/42
top related