Chapter 10 Advanced Network Architectures

1
Chapter 10 Advanced Network Architectures

• Contained Slides by Leon-Garcia and Widjaja

2
Chapter 10 Advanced Network Architectures

• MPLS

3
What is MPLS?
LER
LSR
LSR
IP
LER
IP

• Multiprotocol Label Switching (MPLS)
• A set of protocols that enable MPLS networks
• Packets are assigned labels by edge routers
  (which perform longest-prefix match)
• Packets are forwarded along a Label-Switched Path
  (LSP) in the MPLS network using label switching
• LSPs can be created over multiple layer-2 links
• ATM, Ethernet, PPP, frame relay
• LSPs can support multiple layer-3 protocols
• IPv4, IPv6, and in others

4
Why MPLS?

• Labels enable fast forwarding
• Circuits are good (sometimes)
• Conventional IP routing selects one path, does
  not provide choice of route
• Label switching enables routing flexibility
• Traffic engineering establish separate paths to
  meet different performance requirements of
  aggregated traffic flows
• Virtual Private Networks establish tunnels
  between user nodes

5
Separation of Forwardng Control
All proposals leading to MPLS separate forwarding
and control

• Before MPLS forwarding control intertwined
• Transition to CIDR (control) meant forwarding had
  to change to longest-prefix match
• With MPLS forwarding control are separate
• All forwarding done with label switching
• Different control schemes dictate creation of
  labels label-switched paths
• Control forwarding can evolve independently

6
Labels and Paths

• Label-switched paths (LSPs) are unidirectional
• LSPs can be
• point-to-point
• tree rooted in egress node corresponds to
  shortest paths leading to a destination egress
  router

7
Forwarding Equivalence Class
IP1
IP1
IP2
LER
LSR
LSR
LER
IP1
IP2
IP2

• FEC set of packets that are forwarded in the
  same manner
• Over the same path, with the same forwarding
  treatment
• Packets in an FEC have same next-hop router
• Packets in same FEC may have different network
  layer header
• Each FEC requires a single entry in the
  forwarding table
• Coarse Granularity FEC packets for all networks
  whose destination address matches a given address
  prefix
• Fine Granularity FEC packets that belong to a
  particular application running between a pair of
  computers

8
MPLS Labels
ATM cell
VPI/VCI

• Labels can be encoded into VPI/VCI field of ATM
  header
• Shim header between layer 2 layer 3 header (32
  bits)
• 20-bit label 1-bit hierarchical stack field
  8-bit TTL
• 3-bit experimental field (can be used to
  specity 8 DiffServ PHBs)

9
Label Stacking

• MPLS allows multiple labels to be stacked
• Ingress LSR performs label push (S1 in label)
• Egress LSR performs label pop
• Intermediate LSRs can perform additional pushes
  pops (S0 in label) to create tunnels
• Above figure has tunnel between A G tunnel
  between BF
• All flows in a tunnel share the same outer MPLS
  label

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Label Distribution

• Label Distribution Protocols distribute label
  bindings between LSRs

upstream
downstream
Label request for 10.5/16
LSR 1
LSR 2
(10.5/16, 8)

• Downstream-on-Demand Mode
• LSR1 becomes aware LSR2 is next-hop in an FEC
• LSR1 requests a label from LSR2 for given FEC
• LSR2 checks that it has next-hop for FEC,
  responds with label

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Label Distribution
upstream
downstream
LSR 1
LSR 2
(10.5/16, 8)

• Downstream Unsolicited Mode
• LSR2 becomes aware of a next hop for an FEC
• LSR2 creates a label for the FEC and forwards it
  to LSR1
• LSR2 can use this label if it finds that LSR2 is
  next-hop for that FEC

12
Independent vs. Order Label Distribution Control

• Ordered Label Distribution Control LSR can
  distribute label if
• It is an egress LSR
• It has received FEC-label binding for that FEC
  from its next hop

LER
LSR
LSR
LER

• Independent Label Distribution Control LSR
  independently binds FEC to label and distributes
  to its peers

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Label Distribution Protocol
LSR
LSR

• Label Distribution Protocol (LDP), RFC 3036
• Topology-driven assignment (routes specified by
  routing protocol)
• Hello messages over UDP
• TCP connection negotiation (session parameters
  label distribution option, label ranges, valid
  timers)
• Message exchange (label request/mapping/withdraw)

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MPLS Survivability

• IP routing recovers from faults in seconds to
  minutes
• SONET recovers in 50 ms
• MPLS targets in-between path recovery times
• Basic approaches
• Restoration slower, but less bandwidth overhead
• Protection faster, but more protection
  bandwidth
• Repair methods
• Global repair node that performs recovery
  (usually ingress node) may be far from fault,
  depends on failure notification message
• Local repair local node performs recovery
  (usually upstream from fault) does not require
  failure notification

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MPLS Restoration

• No protection bandwidth allocated prior to fault
• New paths are established after a failure occurs
• Traffic is rerouted onto the new paths

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MPLS Protection

• Protection paths are setup as backups for working
  paths
• 11 working path has dedicated protection path
• 11 working path shares protection path
• Protection paths selected so that they are
  disjoint from working path
• Faster recovery than restoration

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Generalized MPLS

• MPLS
• Connection-oriented
• Leverages IP routing protocols, with TE
  extensions, to provide means for selecting good
  paths
• Provides signaling for establishing paths
• With appropriate extensions, Generalized MPLS can
  provide the control plane for other networks
• SONET networks that provide TDM connections
• WDM networks that provide end-to-end optical
  wavelength connection
• Optical networks that provide end-to-end optical
  fiber path

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Hierarchical LSPs

• GMPLS allows node with multiple switching
  technologies to be controlled by one control
  component
• Notion of label generalized
• TDM slot, WDM wavelength, optical fiber port
• LSP Hierarchy extended to generalized labels
• MPLS LSP over SONET circuit over wavelength path
  over fiber

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Chapter 10 Advanced Network Architectures

• Multimedia Networking

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Multimedia Internet Applications
Remote
Local
Interactive
Continuous Playback
Local Playback
Streaming
Storage
Download
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Multimedia Application Types

• Storage/Download
• Capturing/or downloading multimedia sequences
  to/from storage devices
• Local playback
• Playback of multimedia sequences from a local
  disk
• Streaming
• On-line playback of multimedia sequences stored
  on remote servers
• May pause during playback to account for network
  congestion
• Continuous playback
• Continuous on-line playback of remote multimedia
  sequences
• No pausing allowed
• Interactive
• Multi-participant interactive multimedia sessions

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Multimedia Applications contd
Application Type
Application QoS Requirements
Example
Bandwidth
Errors / Losses
Jitter
Delay
Video Production
High
Medium
Medium
None
Storage
Off-line video editing
Medium-Hi
Medium-Hi
High
None
Download
DVD Playback
Local Playback
N/A
N/A
N/A
None
Real Audio/ Real Video
Streaming
Medium
Low - high
High
Medium
Continuous Playback
Live Broadcast
High
Medium
Low
Medium
Audio/Video Conference
Low
Low
Low
High
Interactive
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Components of Multimedia Applications

• System components
• Capture and playback systems
• Encoders and Decoders
• File storage format and storage devices
• Real-time transport protocol (RTP)
• Real-time Streaming Protocol (RTSP)
• Session Description Protocol (SDP)
• Session Initiation/Announcements protocols
  (SIP/SAP)
• H.323 Multimedia Communications

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Compatibility Requirements
Network
Real-time protocol
Real-time protocol
Compatible CODEC
Encoders
Decoders
File Format
Streaming protocol
Storage
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Multimedia protocol stack
Media Transport
Signaling
Quality of Service
Application daemon
MGCP/Megaco
Reservation
Measurement
H.261, MPEG
H.323
SDP
RTSP
RSVP
RTCP
SIP
RTP
TCP
UDP
IPv4, IPv6
kernel
PPP
AAL3/4
AAL5
PPP
Sonet
ATM
Ethernet
V.34
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Chapter 10 Advanced Network Architectures

• Real-Time Transport Protocol
• RTCP
• RTSP

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Real-Time Protocol

• RTP (RFC 1889) designed to support real-time
  applications such as voice, audio, video
• RTP provides means to carry
• Type of information source
• Sequence numbers
• Timestamps
• Actual timing recovery must be done by higher
  layer protocol
• MPEG2 for video, MP3 for audio

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RTP Scenarios Terminology

• Chair of conference obtains IP multicast address
  pair of consecutive UDP port s
• Even port audio
• Odd port for RTCP stream
• Each media sent on a separate RTP session
• Fixed-length RTP PDUs sent during session
• Each RTP multicasts periodic receiver reports on
  RTCP port
• Mixers and Translators

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RTP Packet Format

• Version (2)
• Padding flag
• Extension Header Flag
• Contributing Source Count ( CSRC IDs)
• Marker (significant events, e.g. frame boundaries)

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RTP Packet Format

• Payload Type e.g. PCM, MPEG2,
• Sequence Number detect packet loss
• Timestamp sampling instant of first byte
• Synchronization Source ID for synch source
• CSRC List contributing sources to payload

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RTP Packet
32
RTP Control Protocol (RTCP)

• RTP companion protocol
• Monitors quality of service at receivers
• Conveys monitored info to senders
• Canonical Name CNAME for each participant
• RTCP Packets
• Sender Report Packet
• Receiver Report Packet
• Source Description (SDES)
• BYE end of participation by sender
• APP application specific functions

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RTCP Packet
34
Real Time Streaming Protocol (RTSP)

• RFC 2326
• VCR-like user control of display play, rewind,
  fast forward, pause, resume, etc
• One connection for control messages
• One connection for media stream
• TCP or UDP can be used for the control channel

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RTSP Operations
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Chapter 10Advanced Network Architectures

• Session Control Protocols
• SIP

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Session Initiation Protocol

• Session association involving exchange of data
  between Internet end systems
• Internet telephone call multimedia
  videoconference instant messaging event
  notification
• Session Initiation Protocol
• Setting up, maintaining, terminating session
• People media devices
• Multicast or mesh of unicast connections
• Support for user mobility
• Over UDP or TCP

38
SIP Protocol

• Text-based client-server protocol with syntax
  similar to HTTP
• Transaction client request /server(s)
  response(s)
• Basic signaling through transactions
• SIP Request method invoked
• INVITE, ACK, OPTIONS, BYE, CANCEL, REGISTER
• INVITE ACK used to initiate calls

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registrar
INVITE sip tom_at_startup.com c IN IPv4
192.168.12.5 maudio 35092 RTP/AVP 0
INVITE sip tom_at_192.168.15.17 c IN IPv4
192.168.12.5 maudio 35092 RTP/AVP 0
(2)
(3)
(5) ringing
(4)
(1)
(6)
(7)
proxy
SIP/2.0 200 OK
SIP/2.0 200 OK
(8)
ACK
(9)
Media flow
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SIP System Components

• User Agents software in end system that acts on
  behalf of a human user
• User Agent Client to initiate a call
• User Agent Server to answer a call
• Network Servers call routing to establish a
  call
• Proxy Server receives request, determines
  server to send it to, and forwards request
  Response flows in reverse direction
• Redirect Server returns message telling client
  address of next server
• Registrar registrations on current user
  locations

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INVITE REQUEST

• INVITE request to UAS of desired user
• Use name, e.g. email address, telephone
• Usually IP address or hostname not known
• As message passes a SIP device, IP address of
  device attached to VIA header
• Used for reverse path
• Command Sequence header
• Request method and sequence number
• Content type default Session Description
  Protocol (SDP)

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Response

• UAC sends INVITE request to network server
• Request proxied/redirected until server found
  that knows IP address of user
• Response message contains
• Same Call ID CSeq To/From
• Reach address to send transactions directly to
  UAS
• Information about media content

43
SIP Ethereal Capture

• user1 calls user2 using Helmsman User Agent
• This User Agent is available at www.sipcenter.com

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INVITE
Description of Invite Packet
45
TRYING
User1 trying to connect to User2
Header Description of Trying Packet
46
RINGING
Packet Description
47
OK and ACK
Packet Description for OK
48
Packet Description for ACK
49
BYE
User2 wants to disconnect, sends a BYE packet
User2 is trying to disconnect and hence sends
Trying Packet
OK is sent by User2 once call is successfully
disconnected
Packet Description for BYE
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Chapter 10 Advanced Network Architectures

• Session Control Protocols
• H.323 Communications Systems

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H.323 Systems

• Support for real-time multimedia communications
  on LANs packet networks
• H.323 provides call control, multimedia
  management, bandwidth management, interfaces to
  other networks
• H.323 terminals carry voice, audio, video, data,
  or combination
• Gateways handle signaling messages between packet
  network other networks
• Gatekeeper handles call control inside H.323 net
• Multipoint control unit combine media streams

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(No Transcript)
53
Scope of H.323
Audio Codec
Receive Path Delay
H.225 Layer
LAN I/F
Microphone Speakers
Camera, Display
Video Codec
Data Equipment
System Control
H.245 Control
System Control User I/F
Call Control
RAS Control
54
H.323 Protocols

• H.225 call control within H.323 net
• RTP/RTCP used for audio/video streams
• H.245 control channel to set up logical
  channels
• RAS registration, admission control, bandwidth
  management
• RSVP Resource Reservation Protocol allows user
  to request a specific amount of bandwidth

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Typical H.323 Stack
H.323
Multimedia Applications, User Interface
Terminal Control and Management
Data Applications
Media Control
RTCP
V.150
T.120
T.38
H.225.0 Call Signaling
H.245
H.225.0 RAS
Audio Codecs G.711 G.723.1 G.729 ..
Video Codecs H.261 H.263 H.264 ..
RTP
UDP
TCP/UDP
TCP
UDP
UDP
TCP
TCP/UDP
IP
56
Basic Call Setup Signaling H.225.0
GW
GW
Optional
57
Call Setup Capture
TCP Control Packets

• No. Time Source
  Destination Protocol Info
• 6 18.904189 192.168.0.149
  192.168.0.143 TCP 1748 gt 1720 SYN
  Seq1739645016 Ack0 Win16384 Len0
• 7 18.905196 192.168.0.143
  192.168.0.149 TCP 1720 gt 1748 SYN,
  ACK Seq4252100644 Ack1739645017 Win17520
  Len0
• 8 18.905366 192.168.0.149
  192.168.0.143 TCP 1748 gt 1720 ACK
  Seq1739645017 Ack4252100645 Win17520 Len0
• 11 19.497846 192.168.0.149
  192.168.0.143 H.225.0 CS Setup-UUIE
• 12 19.769449 192.168.0.143
  192.168.0.149 TCP Desegmented TCP
• 13 20.099818 192.168.0.149
  192.168.0.143 TCP 1748 gt 1720 ACK
  Seq1739645217 Ack4252100649 Win17516 Len0
• 14 20.101044 192.168.0.143
  192.168.0.149 H.225.0 CS Alerting-UUIE
• 16 20.501086 192.168.0.149
  192.168.0.143 TCP 1748 gt 1720 ACK
  Seq1739645217 Ack4252100688 Win17477 Len0
• 20 29.091030 192.168.0.143
  192.168.0.149 TCP Desegmented TCP
• 21 29.329256 192.168.0.149
  192.168.0.143 TCP 1748 gt 1720 ACK
  Seq1739645217 Ack4252100692 Win17473 Len0
• 22 29.330385 192.168.0.143
  192.168.0.149 H.225.0 CS Connect-UUIE
• 23 29.400799 192.168.0.149
  192.168.0.143 TCP 1749 gt 1862 SYN
  Seq1740980379 Ack0 Win16384 Len0
• 24 29.401781 192.168.0.143
  192.168.0.149 TCP 1862 gt 1749 SYN,
  ACK Seq4253464033 Ack1740980380 Win17520
  Len0
• 25 29.401944 192.168.0.149
  192.168.0.143 TCP 1749 gt 1862 ACK
  Seq1740980380 Ack4253464034 Win17520 Len0
• 26 29.405685 192.168.0.149
  192.168.0.143 TCP Desegmented TCP
• 27 29.453530 192.168.0.143
  192.168.0.149 TCP Desegmented TCP
• 28 29.453752 192.168.0.149
  192.168.0.143 H.245 TerminalCapabilityS
  et MasterSlaveDetermination
• 29 29.455958 192.168.0.143
  192.168.0.149 H.245 TerminalCapabilityS
  et MasterSlaveDetermination

H.225.0 setup
Alerting
Connecting
Negotiating Channel Usage
Requesting Bandwidth
58
Data Transfer Capture
RTP video H.263 Packet

• No. Time Source
  Destination Protocol Info
• 62 1240.429251 192.168.0.143
  192.168.0.149 TCP 1862 gt 1749 ACK
  Seq4253464654 Ack1740980896 Win17004 Len0
• 63 1240.429470 192.168.0.149
  192.168.0.143 H.245 OpenLogicalChannelR
  eject OpenLogicalChannelAck OpenLogicalChannelAck
  MiscellaneousCommand MiscellaneousCommand
  OpenLogicalChannelConfirm
• 65 1240.622962 192.168.0.149
  192.168.0.143 RTP Payload typeITU-T
  H.263, SSRC1488263488, Seq12977, Time3017250
• 66 1240.623218 192.168.0.149
  192.168.0.143 RTP Payload typeITU-T
  H.263, SSRC1488263488, Seq12978, Time3017250
• 71 1240.854456 192.168.0.143
  192.168.0.149 TCP 1862 gt 1749 ACK
  Seq4253464654 Ack1740980980 Win16920 Len0
• 72 1240.854730 192.168.0.143
  192.168.0.149 TCP 1503 gt 1752 ACK
  Seq4255085782 Ack1742545885 Win17315 Len0
• 74 1240.915746 192.168.0.149
  192.168.0.143 RTP Payload typeITU-T
  H.263, SSRC1488263488, Seq12980, Time3030750
• 75 1240.916004 192.168.0.149
  192.168.0.143 RTP Payload typeITU-T
  H.263, SSRC1488263488, Seq12981, Time3030750
• 76 1240.916239 192.168.0.149
  192.168.0.143 RTP Payload typeITU-T
  H.263, SSRC1488263488, Seq12982, Time3030750,
  Mark
• 87 1240.977683 192.168.0.149
  192.168.0.143 TCP 1753 gt 1503 PSH,
  ACK Seq1742695460 Ack4255248829 Win17520
  Len25
• 88 1240.979358 192.168.0.143
  192.168.0.149 TCP 1503 gt 1753 PSH,
  ACK Seq4255248829 Ack1742695485 Win17495
  Len21
• 89 1241.212546 192.168.0.149
  192.168.0.143 RTP Payload typeITU-T
  H.263, SSRC1488263488, Seq12983, Time3044070
• 90 1241.212801 192.168.0.149
  192.168.0.143 RTP Payload typeITU-T
  H.263, SSRC1488263488, Seq12984, Time3044070,
  Mark
• 91 1241.231672 192.168.0.149
  192.168.0.143 TCP 1753 gt 1503 ACK
  Seq1742695485 Ack4255248850 Win17499 Len0
• 92 1241.231775 192.168.0.149
  192.168.0.143 TCP 1749 gt 1862 ACK
  Seq1740980980 Ack4253464658 Win16896 Len0
• 93 1241.232617 192.168.0.143
  192.168.0.149 H.245 MiscellaneousComman
  d
• 97 1241.364228 192.168.0.143
  192.168.0.149 RTP Payload typeITU-T
  H.263, SSRC4062428632, Seq32093, Time1885770,
  Mark
• 98 1241.366210 192.168.0.149
  192.168.0.143 TCP Desegmented TCP

More Control
RTP Audio G.723
59
Media Gateway Control Protocols

• Enable simple terminal equipment (i.e. telephone)
  to connect to Internet for IP telephone service
• Two components
• Media Gateway performs media format conversion
  between telephone Internet
• Residential Gateway interacts between telephone
  and call agents in Internet
• Call agents interact with SS7 signaling network
  to setup calls
• Call agents use Media Gateway Control Protocol