1. Packet Switching: LAN to WAN Wired to Wireless Consumer to Enterprise
Notes
Tony Rybczynski

2. Life Senior Member of IEEE
Tony Rybczynski
B.Eng-EE (McGill)
M.Sc- EE (U of Alberta)
Life Senior Member of IEEE
37 years in the industry
10 years with Bell Computer Communications Group as packet switching pioneer
4 years in Bell Northern Research in system engineering
23 years in Nortel Networks mostly in the enterprise business unit
Retired as Director of Strategic Enterprise Technologies (CTO Office)
Over 200 articles, monthly column in trade journal, the ‘Hyperconnected Enterprise’ (TMC) blog and contributor to 2 books
Lecturer in this course since 2000

3. Why is Packet Switching So Important?
is the dominant networking technology
in the Internet,
in public wired and 4G cellular networks
And
in the wired and wireless enterprise

4. Packet Switching in 3 Parts
Part 1: The basic technology
Part 2: The enterprise perspective
Part 3: Not just connectionless packet

5. Part 1: Circuit Switching (TDM) vs Packet Switching
Main differences (TDM vs packet)
Fixed speed vs speed conversion
Fixed delay vs variable delay
Dedicated vs shared bandwidth
Separate vs integrated switching and multiplexing
Call set up vs IP routing
56Kbps
56Kbps
TDM Switch
TDM on SONET
TDM Switch
Mux / Demux
Mux / Demux
10/100/1000Gbps
56Kbps, T1, T3
IP/fibre
Router
Router
Packet Switching is a much more flexible and evolvable technology

6. Packet Switching: A General Definition
Message or bit stream subdivided into packets
Individually addressed packets
Dynamic bandwidth
Access and trunk multiplexing
Traffic bursts at full pipe capacity
Layered operation
Application protocols above
Transmission facilities/pipes below
Seven Layer OSI model helps- packet switching applied at Layer 2 and 3
Exploitation of 'bursty' nature and tolerance to delays of most applications
Functionality: routing, flow control, error control, Quality of Service (QoS) …
“OSI”: Open System Interconnection

7. Packet Switching Time Line
Ethernet (’80)
Token ring et al
TCP/IP (’83)
Academic Internet
Research
Nets for
robust data
comm
Voice and video
Over IP
Mobility
ARPAnet (‘72)
Commercial X25 nets (‘76)
4G wireless
Gaming
IPTV
Storage/IP
Commercial Internet (’94)
Frame relay/ATM
1960s s s s ’s Present

8. Many Faces of Packet Switching
A set of technologies
Switching & multiplexing architecture
Packet formats
Connectionless or connection-oriented paradigms
Transportable on different media at varying speeds
LAN/MAN/WAN/wireless networks
A carrier service capability
Basis for tarriffed services
Unicast and multicast
A set of open standards
Interface and networking standards
User and network interface protocols
Service definitions
Performance metrics
Security
Adaptation and encapsulation standards
“LAN/MAN/WAN”: Local/Metro/Wide Area Net

9. Scope of This Lecture Layer 4-7 (TCP, UDP, RTP etc)
Layer 3 Network Layer (today IP)
IP addressing (e.g )
Basic delivery with QoS optional
Layer 2 Link layer (Ethernet MAC, HDLC)
Packet delineation
Variable time delay, error free
Optional QoS, flow control and error recovery
Link addresses (e.g. MAC address: 0007E08CBB04)
Layer 1 Physical Layer (copper, fibre, wireless)
Transmission of a serial bit stream
Dedicated path between two parties
Shared path among multiple parties (e.g. wireless)
OSI Stack
Application
Presentation
Session
Transport
Network
Link
Physical
“TCP”: Transmission Control Protocol
“UDP”: User Datagram Protocol
“RTP”: Real-Time Protocol
“MAC”: Media Access Control
“HDLC”: High Level Data Link Control

10. IP is THE Network Layer Standard
Data
Voice
Video
Multimedia
Gaming
File sharing
IP TV
Telemetry
Applications
Network Layer
Layer 4-7 ‘IP Suite’ IP
Any Layer 2
Fiber DWDM
SONET
Copper
Wireless
Security can be applied in all layers as appropriate
“DWDM”: Dense Wave Division Multiplexing
“SONET”: Synchronous Optical NET

11. The Standard Layer 3… IPv4
Origins >30 years ago (ARPAnet)
Connectionless/”datagram” networking (not sequence preserving, lossy)
4 Byte IP address per packet
Full suite of networking protocols
Routing protocols (e.g. RIP- Routing IP, OSPF- Open Shortest Path First)
Multicast (e.g. IGMP- Internet Group Membership Protocol, DVMRP- Distance Vector Multicast Routing Protocol, MOSPF- Multicast OSPF, PIM- Protocol Independent Multicast)
QoS and traffic management (RSVP- Resource reSerVation Protocol)
IPv6 is starting to be deployed!
First Asia, public wireless and DoD
Required for address scalability (16 B addresses) and increased security (IPsec)
OSI Stack
Application
Presentation
Session
Transport
Network
Link
Physical
“FTP”: File Transfer Protocol

12. Example: Packet Formats
Layer 2
Header
Level 3
Header
Level 4-7
Headers
Data (0-1500B)
HDLC
Trailer
Flag
Flag
IP: 20B (40B for IPv6) including two addresses
Ethernet: 18 B (bytes)
Point to Point PPP: 5B including opening sequence
UDP: 8B including source/destination port addresses
TCP: 20B including port addresses, sequence numbers and window controls; connection setup requires 3-way handshake
Layer 4
RTP: 12B including timestamps (for voice); more for data
Trailer (Layer 2): 2-4B CRC
“CRC”: Cyclical Redundancy Check

13. Queuing and Packet Switching
Router
output
inputs 10 5
Total time
Service time
utilization %
Queuing introduces variable delays
Congestion control required to protect the network
Quality of Service (QoS) mechanisms for time critical traffic

14. Routing Challenges in Packet Networks
Switch/
Router
“C”
Switch/
Router
“A”
Switch/
Router
“E”
Application Server
Switch/
Router
“B”
Switch/
Router
“D”
Links can have
Different speeds
Different utilizations
Different delays
Different operational states (up or down)
Routing system has two objectives:
Maximize network utilization and minimize routing convergence times
Meet user/application needs

15. Routing Options Flat vs hierarchical (for scalability)
Switch/
Router
“C”
Switch/
Router
“A”
Switch/
Router
“E”
Application Server
<<RP>>
<<RP>>
<<RP>>
<<RP>>
Switch/
Router
“B”
Switch/
Router
“D”
Routing Protocol exchanges routing information periodically
<<RP>>
Routing Table is maintained and specifies what is “best” link to take for each destination
Flat vs hierarchical (for scalability)
Static vs dynamic routing
Distance Vector (e.g. hop count to each destination) vs Link State Routing (each node has network view)
Per packet vs per flow
Added requirements
Load balancing
Policy-based routing
‘Cost’ of links

16. Packet Switching Performance Parameters
Transit delay: time from transmission to reception
Access link delay (queuing time, emission time, propagation time)
Network transit delay ( access + switch + trunk delay)
Average vs distribution of delays
Throughput
Switch
Trunk
Access
User application
Measures of efficiency
Processor and trunk utilization
% overhead for payload
Challenges (just like highway 417)
Traffic characterization (driver behaviour and prioritization)
Protecting the network (maximizing cars/minute)
Networking objectives:
Maximize network utilization
Meet user/application needs

17. Packet Switching: Advantages/Disadvantages
Bandwidth only consumed when needed
Reduced cost of bandwidth
Reduced cost sensitivity to distance
Speed conversion
56Kbps modem access to 100GigE server
Dynamic routing
Connection
Connectionless
Leveraging of end point processing
Flow and error control
But ...
Processing requirements per packet
Complexity
Routing algorithms
Congestion control
Protocols
Variable delays

18. Part 2: The Enterprise Perspective
Business IT needs:
To do more with less
To drive employee productivity wherever they are
To use IT to grow revenues
To use IT to anticipate customer requirements
Time
Traffic
Applications
IT Budget
The CIO’s dilemma
Threats
Message:
Here’s a high level opener to initiate dialog with the customer on his/her priorities and challenges.
We focus on CIO’s environment to make you successful.
Large corporations want to leverage carrier IP and non-IP services, with best bang for the buck, control, security and reliability.

19. Large Business and Government Organizations….
have very large internal IP networks (often with private IP addresses)
are reluctant to expose their internal traffic to Internet insecurity etc
have economic access to raw bandwidth
can suffer large economic loss from network and security failures
need management control to respond to internal business owners and their customers

20. Example of Large Campus Network
5000 employees
10,000 10/100 and 10/100/1000 Mbps ports to desktops and servers
Resilient Ethernet switches in 50 wiring closets (<100m to each desk)
12 redundant Ethernet Routing switches in backbone
Hundreds of WLAN Access Points
>100 Gbps uplink capacity and >Tbps switching capacity
Layered security
Centralized control
Applications:
Hundreds of business apps, Collaboration, Social networking, , Instant Messaging, Video and Audio Streaming

21. High-performance level maintained in case of a switch failure
Ethernet Switching to the Desktop
Dedicated bandwidth to each desktop
Standard Carrier Sense Multiple Access (CSMA)/ Collision Detection
100 meter wired range
Flat MAC addressing space
Power over Ethernet (for VoIP, WLANs, security devices)
Standard QoS
10/100/1000 Gbps
Over Category 5 wiring
High-performance level is maintained even in case of a failure.
If a cable is disconnected, the performance drops only by 80 Gbps. The total stack bandwidth in this case is = 580 Gbps (88% of 640 Gbps).
If a switch were to fail, the performance may drop by 160 Gbps. The total stack bandwidth in this case will be = 480 Gbps (75% of 640 Gbps)
With traditional ring architecture design, the performance may drop by 50%. But with FAST design, the performance is maintained at a high bandwidth.
This diagram also shows the fail-safe stacking feature. If a switch were to fail in a stack, all the other switches in the stack continue to function as a stack. For fail-safe stacking, the cascade return cable must be connected (as shown in the diagram).
High-performance level maintained in case of a switch failure

22. Wireless Ethernet (802.11)
Cell “B”
Cell “A”
Ethernet
Switch
Workstation
Ethernet Segment
(10BaseT or 10/100 autosense)
Access Point
Access Point
Powered
Over Ethernet
Multiple standard modes: Mbps; 13
Low power unlicensed operation over limited distances (<100m indoors)

23. Ethernet Routing Switches
Network View
Mobile
user
WLAN & cellular
DSL
Cable modem
Ethernet
Branches &
remote sites
Larger sites
Data centres ?
Customer or
Telecommuter
The Internet
WAN VPN Router
LARGE CAMPUS
Campus core/distribution
Aggregation/Access
Edge (Wiring Closet)
Campus backbone
Ethernet Routing Switches
Ethernet Switches
Database
Application Server
WLAN
Laptop
“VPN”: Virtual Private Network
“DSL”: Digital Subscriber Line
“3G CDMA/GSM”: third gen public wireless 3

24. Enterprise Inter-Site Connectivity Options
Campus networks
Regional
center
Branch networks
Data centres HQ
Branch
Remote
office
Many Layer 1 options
Private lines
Dark fibre
Fibre rings with DWDM
SONET rings
Layer 2 Packet Services
Ethernet connectivity
Layer 3 VPNs
MPLS and/or IPSec over public IP
Business
Apps
&
Storage
Messages:
Nortel is the #2 in the data space. Nortel offers both best in class solutions for multivendor networks and is the only one of two vendors who can offer comprehensive end-to-end converged networking and security solutions
On the diagram:
The boxed areas identify solutions areas that can be targeted with Nortel products in a multivendor environment.
The functionality in the cloud is offered by Nortel as part of an end-end solutions.
Service providers developed ‘Layer 2’ packet services:
Ethernet services
Multiprotocol Label Switching (MPLS)

25. Part 3: Not Just Connectionless IP Packet
Switching &
Multiplexing
Packet Switching
Statistical Multiplexing
Circuit Switching
TDM Multiplexing
Connection-
Oriented
Connectionless
Layer 3 IP
Layer 2.5 MPLS
Layer 2 Frame Relay/ATM
Layer 2
Ethernet
Copper/fibre MAN/WAN
Wired MAN
Wireless LAN/MAN
Carriers developed connection-oriented & connectionless ‘Layer 2’
packet services to meet enterprise needs
MPLS was also developed as carrier backbone technologies
for enhanced traffic management capabilities

26. Connection-oriented Packet
Nailed up connections C B
Connections could be frame (Frame Relay) or IP-based (e.g. MPLS)
Switching based on connection-ids (MPLS labels)
Enterprise site-site IP runs over these connections
Segregation from public Internet
Handling of private enterprise IP addressing
Improved security and control
Economics of packet for enterprise connectivity

27. MultiProtocol Label Switching (MPLS)
MPLS allowed carriers to meet enterprise needs, AND
to address traffic management challenges in their public IP networks
Connectionless IP
Connection-oriented
packet
MPLS
IP routing
software
IP routing
software
Connection
control plane
Label Swapping
Label
swapping
Forwarding
IP control plane for topology and addressing
QoS defined for transport of IP traffic
Label swapping paradigm for VPNs & traffic management

28. Let’s End With A Reality Check
Everything on IP and IP on everything
Simplification via bandwidth
Access is split across multiple technologies
Ethernet for desktops (may be displaced by WiFi)
WiFi for mobile hotspots
DSL, cable and some fiber to homes
2-4G public wireless
Carrier backbones evolving to Ethernet MANs and MPLS WANs for public Internet and enterprise VPNs

29. What’s Hot in Packet Switching?
Making IP networks more scaleable and improving economics
Explosion in broadband wireless including n
Beyond 10 Gbps Ethernet (40 or 100?)
Terabit switch routers (hardware/hardware/hardware)
Evolution/transition to IPv6 for end-to-end addressing scalability
Security everywhere
Expanding application fit of IP networking
Sensors
4G Internet-optimized public wireless
IPTV
Storage on IP
More gaming
Debate: application-fluent network intelligence
Lots of Opportunities for You!

30. A Parting Thought Technology is not an end in itself!
It has to take you where the user wants to go

31. For More Information Bon Voyage and Thank You On packet switching
“Commercialization of packet switching ( ): A Canadian perspective” by T.Rybczynski
On all things IP
On all things wired and wireless Ethernet
+ Course lectures on:
VoIP, Internet of Things, WiFi, Internet Technology and Large-scale IP Network Design
Bon Voyage and Thank You