7/29/2019 Rcom.lecture10.Label Switching
1/51
R. MORLA 2011
Computer Networks
Label switching
Lecture note 10
MIEEC
7/29/2019 Rcom.lecture10.Label Switching
2/51
R. MORLA 2011
Label switching
7/29/2019 Rcom.lecture10.Label Switching
3/51
R. MORLA 2011
Switching: circuit, virtual
circuit, and datagram
7/29/2019 Rcom.lecture10.Label Switching
4/51
R. MORLA 2011
Virtual circuits
Built on top of datagram network
Each packet follows the same path Can do per circuit:
Admission control
Resource reservation
Can do traffic engineering Specify capacity per VC
Choose paths for VCs based on VC capacity andavailable network resources
Can understand the network usage
7/29/2019 Rcom.lecture10.Label Switching
5/51
R. MORLA 2011
VC vs. Datagram Networks
7/29/2019 Rcom.lecture10.Label Switching
6/51
R. MORLA 2011
Forwarding:
Longest prefix match
7/29/2019 Rcom.lecture10.Label Switching
7/51
R. MORLA 2011
Forwarding:
Virtual circuits
7/29/2019 Rcom.lecture10.Label Switching
8/51
R. MORLA 2011
Production network
7/29/2019 Rcom.lecture10.Label Switching
9/51
R. MORLA 2011
Production network
Whats the underlying topology?
Point to point?
Ethernet switches?
IProuter
IProuter
IProuter
IProuter
IProuter
IProuter
IProuter
IProuter Layer 3 IP
7/29/2019 Rcom.lecture10.Label Switching
10/51
R. MORLA 2011
Production network
Layer 1 DWDMDWDM
DWDM
DWDM
DWDM DWDM
DWDM
SONETSONET
SONET
SONETSONET
SONET
SONET
SONET
SONET
SONET
Layer 2 SDH/SONETDWDM
ATM
MPLS
ATM
MPLS
ATMMPLS
ATMMPLS
ATMMPLS
ATM
MPLS
ATMMPLS
Layer 2 ATM/MPLS
IProuter
IProuter
IProuter
IProuter
IProuter
IProuter
IProuter
IProuter Layer 3 IP
7/29/2019 Rcom.lecture10.Label Switching
11/51
R. MORLA 2011
Production network
Layer 1 DWDMDWDM
DWDM
DWDM
DWDM DWDM
DWDM
SONETSONET
SONET
SONETSONET
SONET
SONET
SONET
SONET
SONET
Layer 2 SDH/SONETDWDM
ATM
MPLS
ATM
MPLS
ATMMPLS
ATMMPLS
ATMMPLS
ATM
MPLS
ATMMPLS
Layer 2 ATM/MPLS
IProuter
IProuter
IProuter
IProuter
IProuter
IProuter
IProuter
IProuter Layer 3 IP
Packet in Packet out
7/29/2019 Rcom.lecture10.Label Switching
12/51
R. MORLA 2011
DWDM network
7/29/2019 Rcom.lecture10.Label Switching
13/51
R. MORLA 2011
SDH/SONET
7/29/2019 Rcom.lecture10.Label Switching
14/51
R. MORLA 2011
SDH/SONET
7/29/2019 Rcom.lecture10.Label Switching
15/51
7/29/2019 Rcom.lecture10.Label Switching
16/51
R. MORLA 2011
MPLS
Label switching coexists
with IP longest-prefix match
7/29/2019 Rcom.lecture10.Label Switching
17/51
R. MORLA 2011
OSPF, etc.
7/29/2019 Rcom.lecture10.Label Switching
18/51
R. MORLA 2011
Switching: circuit, virtual
circuit, and datagram
7/29/2019 Rcom.lecture10.Label Switching
19/51
R. MORLA 2011
Switching: circuit, virtual
circuit, and datagram
Circuit switching:Digital synchronous
multiplexing(SDH, Sonet),
DWDM
Datagramswitching:CIDR lookup
OSPF, BGP
Virtual circuit switching:ATM, MPLS
7/29/2019 Rcom.lecture10.Label Switching
20/51
R. MORLA 2011
Label switching: ATM evolution to MPLSAsynchronous Transfer Mode
Multiprotocol Label Switching
7/29/2019 Rcom.lecture10.Label Switching
21/51
R. MORLA 2011
ATM
Designed to become the next step after ISDN,
BISDN, etc. Designed to offer integrated networkservices, meaning:
Constant bitrate, variable bitrate Audio, video, etc.
Single network infrastructure, multipleapplications
Based on fixed-size packets (cells) With adaptation protocols for each application
7/29/2019 Rcom.lecture10.Label Switching
22/51
R. MORLA 2011
Applications => cells =>
single transfer mode
N
etwork
7/29/2019 Rcom.lecture10.Label Switching
23/51
R. MORLA 2011
Applications => cells =>
single transfer mode
Cells
7/29/2019 Rcom.lecture10.Label Switching
24/51
R. MORLA 2011
ATM packet switching
7/29/2019 Rcom.lecture10.Label Switching
25/51
R. MORLA 2011
ATM virtual paths and channels
7/29/2019 Rcom.lecture10.Label Switching
26/51
R. MORLA 2011
ATM
Vision 1
Replace IP Applications/hosts all become ATM-speakers
Vision 2
Provide services at the core network ATM overlay network
Traffic engineering, QoS
Overall interesting ideas, wrong approach
L b l it hi
7/29/2019 Rcom.lecture10.Label Switching
27/51
R. MORLA 2011
Label switching:
Overlay vs. peering
Overlay of virtual circuits
Direct peering of routers
Two networks to
manage!
7/29/2019 Rcom.lecture10.Label Switching
28/51
R. MORLA 2011
MPLS
Take the label switching concept
Good for: Traffic engineering
Network control and planning
Apply it to the IP network Not as an overlay network
7/29/2019 Rcom.lecture10.Label Switching
29/51
R. MORLA 2011
MPLS encapsulation format
Shim layer
2.5 layer
MPLS data encapsulatedbetween Layer 2 and
Layer 3 Ethernet and IP
Labels may be
pushed/popped at
intermediate routers
7/29/2019 Rcom.lecture10.Label Switching
30/51
R. MORLA 2011
MPLS scalability via aggregation
One labelswitched
path (LSP) Can
aggregatemultiple IPflows
Aggregationon Edge
Label SwitchRouter (LSR)border
7/29/2019 Rcom.lecture10.Label Switching
31/51
R. MORLA 2011
Aggregation in core
7/29/2019 Rcom.lecture10.Label Switching
32/51
R. MORLA 2011
MPLS tunneling
7/29/2019 Rcom.lecture10.Label Switching
33/51
R. MORLA 2011
MPLS Control Plane
Label Distribution Protocol
Destination-based / control-driven Computed according to IP route
MPLS
7/29/2019 Rcom.lecture10.Label Switching
34/51
R. MORLA 2011
MPLS
LDP control-driven example
7/29/2019 Rcom.lecture10.Label Switching
35/51
R. MORLA 2011
MPLS Explicitly-routed LSP
LSP specified by operator or network
management system Route specified in LDP setup message
Message sent to all LSR in the route
Each LSR sends label request to next-hop LSR
Path independent of IP routes
Opens the door to traffic engineering
Constrained-based Routed LDP
7/29/2019 Rcom.lecture10.Label Switching
36/51
R. MORLA 2011
Constrained-based Routed LDP
CR-LDPLSR A requires route/resources to LSR C
1. LSRA computes path to LSR C
2. LSRA reserves resources, sends label request andtraffic parameters to LSRB/C
3.
4. LSRC checks for resources. If available send mappingmessage to LSRB
5. LSRB does the same, mapping original LSP id
7/29/2019 Rcom.lecture10.Label Switching
37/51
R. MORLA 2011
MPLS with RSVP
Resource Reservation Protocol
Similar to CR-LDP except resources arechecked on the return path
7/29/2019 Rcom.lecture10.Label Switching
38/51
R. MORLA 2011
RSVP vs. CR-LDP
State-full vs. state-less
CR-LDP uses TCP
Hard state
needs explicit label unbinding message RSVP
Uses UDP
Soft state, needs to periodically refresh state Detects changes automatically
7/29/2019 Rcom.lecture10.Label Switching
39/51
R. MORLA 2011
Generalized Multiprotocol Label switching
7/29/2019 Rcom.lecture10.Label Switching
40/51
R. MORLA 2011
TO THINKTO THINKTO THINKTO THINK
MPLS applies to packet switching
Can we apply the same label switchingconcept to the rest of the network?
Time slots (TDM)
Wavelengths (DWDM) Physical fibers
G l
7/29/2019 Rcom.lecture10.Label Switching
41/51
R. MORLA 2011
Goal
Fast and automated way to create
On-demand circuits
N t k hi h
7/29/2019 Rcom.lecture10.Label Switching
42/51
R. MORLA 2011
Network hierarchy
FiberWDM
TDM
Packets
S it hi Hi hi
7/29/2019 Rcom.lecture10.Label Switching
43/51
R. MORLA 2011
Switching Hierarchies
Fiber WDM TDM PacketsPackets WDMTDM
Fiber switching
switching
Timeslot switching
Packet switching
S it hi biliti
7/29/2019 Rcom.lecture10.Label Switching
44/51
R. MORLA 2011
Switching capabilities
Timeslot, TDM(SONET/SDH) Wavelength (lambda) Waveband (sets of lambdas) Port (fiber) switching
G li d l b l
7/29/2019 Rcom.lecture10.Label Switching
45/51
R. MORLA 2011
Generalized label
Fiber id in a fiber bundle,
Waveband in a fiber Wavelength within waveband/fiber
Timeslot within a wavelength MPLS/ATM packet switching label
Hierarchical LSP set p
7/29/2019 Rcom.lecture10.Label Switching
46/51
R. MORLA 2011
Hierarchical LSP setup
Un-established connectionsBi-directional connections
Hierarchical LSP setup
7/29/2019 Rcom.lecture10.Label Switching
47/51
R. MORLA 2011
Hierarchical LSP setup
MPLS vs GMPLS issues
7/29/2019 Rcom.lecture10.Label Switching
48/51
R. MORLA 2011
MPLS vs. GMPLS issues
Control and data could be delivered ondifferent paths
Labels must have meaning (map toresources)
Stacking: tunnels in packet networks,physical hierarchies for others
Set/Delete paths can be more complex
than removing labels from forwardingtable
MPLS vs GMPLS issues
7/29/2019 Rcom.lecture10.Label Switching
49/51
R. MORLA 2011
MPLS vs. GMPLS issues
Label set
No wavelength conversion Same wavelength pool across the optical
network
Contention on wavelengths
7/29/2019 Rcom.lecture10.Label Switching
50/51
R. MORLA 2011
How are virtual circuits implemented over datagramnetworks?
What are the advantages and disadvantages of virtualcircuits?
What are the technologies typically used in aproduction network?
Why is MPLS called a 2.5 layer protocol? How does MPLS scale?
What are the advantages and disadvantages of a hard-state vs. soft-state protocol?
What are the network technologies that are managedby the GMPLS protocol?
What does label stacking mean in GMPLS?
HOMEWORKHOMEWORKHOMEWORKHOMEWORK
7/29/2019 Rcom.lecture10.Label Switching
51/51
R. MORLA 2011
HOMEWORKHOMEWORKHOMEWORKHOMEWORK
Review slides
Read from Kurose
Section 5.8 Link virtualization
Do your Moodle homework