Transcript University of Tehran

Advanced topics
in
Computer Networks
Lecture 1: Introduction
University of Tehran
Dept. of EE and Computer Engineering
By:
Dr. Nasser Yazdani
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Outline
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Agenda
Policy, Grading, reading materials, etc.
Overview of course materials
Computer Network trend
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Agenda
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To establish a base for future computer networks
research and development.
To discuss latest developments in computer
networking and telecommunications via class
lectures and assigned readings.
To find the current research issues in the field.
Finally, prepare to perform some projects in
computer networks which are essential in national
development, designing and building switches,
routers, etc.
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Course Materials
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Course Web page
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Research papers
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visit regularly
Printed papers or pdf/ps format on the Website
Combination of classic and recent work.
Class notes of Dr. Turner on switching.
Textbooks
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For Class reading
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“ATM switching systems” by Thomas M. Chen and ..
“MPLS technology and Applications” by Bruce Davie and ..
Background reading, so many books including:
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“Computer Networks, A system approach. Peterson & Davie 2nd
edition
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Grading
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Homework assignments, around %20
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Presentations
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One paper presentation, around 1 hour.
Final project presentation, around 20 minutes.
One hands-on assignment.
Severe late penalties!
Project around %45
Exam, final around %40.
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Policy
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The course is research oriented. Then, the
main focus will be project and paper
reading.
We will focus more packet switch, but open
to new areas like mobile and wireless
networks, QoS, etc.
There will be a lot of reading and work.
Then, be prepared!.
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Covered topics
The focus point of the course will be packet
switching covering the following topics:
1.
2.
3.
4.
5.
6.
ATM networks
Switching architecture.
Lan switching, bridges, IP over ATM.
IP lookup
Packet classification
Label Switching.
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7.
Tag switching, IP switching.
Multiprotocol Label switching (MPLS
Network processors (?)
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Asynchronous Transfer
Mode Networks (ATM)
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ATM networks introduced commercially in
early nineties.
» designed to match packet networks’ ability to serve
many different applications
» improve support for real-time applications by
allowing bandwidth reservation and support for
guaranteed Quality of Service (QOS)
» improve support for multicast applications with
built-in signaling mechanisms
» improve performance through high performance,
scalable hardware switching
» improve scaling using general hierarchical
addressing and two multiplexing levels
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ATM (Cont)
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Overall characteristics
» cell-based switching with virtual circuit and virtual
path routing
» short, fixed-length cell to facilitate hardware
switching & reduce delay variability
» hardware support for unicast and multicast
forwarding
» general signaling protocol for establishment of
unicast and multicast sessions
» comprehensive traffic management framework
supporting bandwidth reservation and QOS;
emphasis on high quality services.
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ATM (Cont)
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Competition between IP & ATM has
improved both.
» efforts to add QoS and multicast signaling
capabilities to IP
» introduction of hardware switching
techniques in IP routers
» improved congestion control mechanisms
for data in ATM
» extending ATM multicast to support manyto-many
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Switching
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Switching systems
» use cell labels to forward cells to destination
» accommodate differences in terminal devices
» allow large networks to be built economically
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Cell switches must be “programmed” to
forward cells.
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Switching (Cont)
Input and Output Transmission
Interfaces (ITI, OTI)
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»convert between serial
optical signals and parallel
electrical signals
»extract timing from received signals
»encode (and decode) data
for transmission
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Input Port Processors (IPP)
» synchronize received signals
» determine required output or outputs using routing table
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Output Port Processors (OPP)
»queue outgoing cells
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Shared bus interconnects IPPs and OPPs.
Control Processor (CP)
» configures routing tables to implement end-to-end channels
» accepts requests for channels from terminals
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» coordinates end-to-end
channel setup together with CPs in neighboring
Layer 2 switching
Interlan switches, bridge are powerful but not
scalable to WAN.
Problem with Layer 2 switching is that it takes
network as a flat network.
Virtual LANS is used to overcome location limitation
for LAN.
VLAN is a broadcast domain, emulates the idea of
being in the same physical LAN.
More Flexible, Secure, Efficient compare to LANS
By appending a Tag to the packet which identifies the
VLAN.
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WAN Switching
There are two major problems in scaling LAN
switching to WAN.
 Broadcast storm on the net.
 The size of lookup table.
Switch needs a way to identify output port
without broadcasting at startup.
 Use existing switching technology to send
IP ( IP over ATM)
 Identify each flow with an ID.
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IP Lookup
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Packets are forwarded to their
destination based on their destination
addresses.
Router must find the address of the next
hop for each packet by finding the
longest prefix matching with the packet
destination address.
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IP lookup (Cont)

Example:
If the a packet destination
address is 101100111,
the next hop will be 3
since 1011001 is the
longest matching prefix.
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Packet Classification
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Security and Filtering. Block unauthorized
access. It is important on the access point
of a network.
Differentiated Services.
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Quality of Service.
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Policy based routing.
Billing.
Isolating traffic from different users
Special queuing and scheduling.
Traffic shaping.
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General View
Routing
Classifier
State
Filter Action
Scheduler
Output driver
Input driver
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IP output
Processing
IP Packet
IP Packet
IP input
Processing
Reservation,
Signaling &
Management
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General framework
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Each filter or rule consist of two sections,
packet header information and actions or rule
Packet headers
Header
1
Header
2
….
Rule or Action
Header K
• Header information uniquely identify packet of a flow.
• Rule can be for security, forwarding or QoS of service rule.
Questions?
 Which combination of header fields?
 How to formulize and map QoS, InterServ, DiffServ, etc.
parameters to these rule?
 How MPLS can be coupled with this classification scheme?
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TAG Switching
The idea is to identify a flow with an ID.
It combines label swapping with network
layer routing.
It is the base of MPLS, Multiprotocol Label
Switching, protocol.
It was originally proposed by CISCO.
The Components:
 Forwarding
 Control. Maintaining correct tags.
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TAG Switching (Cont)
Forwarding: is based on Label swapping.
Each packet carry a tag, id with itself.
There is a Tag Forwarding Information
Base(TFIB) table in the switch.
Incoming Tag
Outgoing Tag Outgoing
interface
Outgoing link
level inform.
If the switch finds a entry with the incoming tag, it
replaces the tag in the packet with the outgoing tag
and the link information, and forwards it to the
outgoing interface.
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MPLS (Multiprotocol label
switching)
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To utilize ATM switching technique in IP routers.
This improve the price/performance of
forwarding process.
To simplify forwarding and routing process. Use
MPLS tags for forwarding instead of IP header.
This improve scalability of network layer
forwarding.
To extend the functionality and flexibility in
bringing new services such as traffic shape, QoS,
etc in an easy and manageable manner.
And more …..
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Quality of Service
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Related topics
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Signaling and admission control.
Traffic shaping
Scheduling
Buffer management
Constrained based routing
Quality of Service protocols for IP
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Integrated services
RSVP
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Network processor
We can identified two almost
independent parts in the design.
64 bits
SRAM
64 bits
PHY
64 bits
NP0
64 bits
32 bits
SRAM
ALU
32 bitsNP1
16 bits
32 bits
Inter
face
Switch
SRAM
64 bits
Network Processor
We are using two chips to implement the whole functionalities.
We call each chip network processor for the sake of simplicity.
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Network processor (Cont)
The first Network Processor (NP0) does:
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Parsing
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Writing ingress packets in the SRAM
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Filtering
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Classification
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Reading and Dispatching egress packets to
the Physical line.
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Sending packet headers to ALU for routing
and NP1 for scheduling.
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Network processor (Cont)
The Second Network Processor (NP1) does:
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Scheduling
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Queuing
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Reading ingress packets from the SRAM
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Dispatching ingress packets to the switch.
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Receiving egress packet from switching and
writing them into the RAM.
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Signaling for port and physical address
finding.
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Outline




Agenda
Policy, Grading, reading materials, etc.
Overview of course materials
Computer Networking trends
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29
Trends
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Technology trends.
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Driving forces.
Fast Immediacy
Impact on R&D
Impact on Education
Convergence
Information Glut
Networking Trends
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Driving forces
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Exponential growth.
Number of Hosts on the
Internet:
1E+09
Aug. 1981
213
Oct. 1984
1,024
Dec. 1987
28,174
Oct. 1990
313,000
Oct. 1993
2,056,000
Apr. 1995
5,706,000
Jul. 1997 19,540,000
Jul. 1999 59,249,900
Jul. 2001 117,288,000
1E+07
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1E+08
1E+06
10000
10000
1000
100
10
1
1981
1985
Adv. topics in Computer Network
1989
1993
1997
2001
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