university of technology computer science department network administration branch first class

University of TechnologyComputer Science DepartmentNetwork Administration Branch

First Class

Principles of Network Algorithms

Second Semester – 2012

Prepare by: Dr. Mazin S. Ali

available at: www.uotechnology.edu.iq/dep-cs

Resource:The University California, San DiegoComputer Science and Engineering

Lecture Notes of Professor George Varghesehttp://www-cse.ucsd.edu /~varghese

2

Lecture1:Introduction and Principles of Network Algorithms

Contents: 1. Algorithm (Definition) 2. Computer Network (Definition)

3. Network Components (NIC, Access Point, Repeater, HUB, Bridge, Switch, Router, BRouter, GATEWAY)

4. Network Bandwidth (Definition)

5. Network Algorithms 6. Routing (Routing Protocols, Routing Table, Routing Configuration) 7. Capacity of Router 8. History of big Routers (Short History)

3

Lecture 2:Lookup and Router Architecture

Contents: 1. Short Review 2. Routing Table Lookup 3. Router Architecture (Input Port Processing, Switching Fabrics,

Routing Processing, Output Port Processing)

4

Lecture 3:Searching Routing-Table Algorithms

Contents: 1. Searching Algorithm (Definition)

2. Searching Routing Table (Definition)

3. Searching Routing Table Algorithms 3.1. Binary Search. 3.2. Hash Table. 3.3. Tire based Algorithms: 3.3.1. 1-Bit Trie (BMP) Algorithm 3.3.2. Multi-Bit Tire (VST) Algorithm 3.3.3. Compressed Tries 4. Tire based Algorithm for Strings

5


Contents: 1. Searching Algorithm 2. Searching Routing Table 3. Searching Routing Table Algorithms 3.1. Binary Search. 3.2. Hash Table. 3.3. Tire based Algorithms: 3.3.1. 1-Bit Trie (BMP) Algorithm 3.3.2. Multi-Bit Tire (VST) Algorithm 3.3.3. Compressed Tries 4. Tire based Algorithm for Strings

6

Lecture 5:Packet Classification

Contents: 1. Network Reference Models 2. TCP/IP Reference Model (IP Protocol Stack)

2.1. The Application Layer2.2. The Transport Layer (Host-to-Host) (End-to-End)

2.3. Internet Layer2.4. Network Layer (Host-To-Network) (Link)

3. ICMP and OSPF Core Protocols 4. IP v4 and IP v6 Packets 5. TCP and UDP Packets 6. Simplified Network Packet Format 7. Screening Router

7

Lecture 6:Packet Classification (Cont.)





8

Lecture 7:Switching Theory

Contents: 1. Short Reviewing 2. Switching Theory 3. Crossbar Switch Architecture 4. Crossbar Switch Models IQ Switch OQ Switch CIOQ Switch

9

Lecture 8:Switching Theory (Cont.)

Contents: 1. Review 2. Speed Up and Delay Control in CIOQ 3. Stable Marriage Algorithms for CIOQ Gale-Shapley Algorithm (GSA) 4. Scheduling Algorithms for CIOQ First In First Out Scheduling Algorithm (FIFO) Most Urgent Cell First Scheduling Algorithm (MUCF) Randomized Switch Scheduling

10

Lecture 9:Bandwidth Partitioning

Contents: 1. Review 2. Network Bandwidth 2.1. Network Bandwidth – Network Centric Approach 2.2. Network Bandwidth – User Centric Approach

11

Lecture 10:IP Addressing

Contents: 1. IPv4 Addresses 2. Classful IPv4 Addressing Scheme 3. Public and Private IP Addresses 4. Reserved IP Addresses 5. Subnetting / Netmask 6. NAT (Network Address Translation)

12


First Class


Lecture 1:Introduction and Principles

of Network Algorithms


Lecture1:Introduction and Principles of Network Algorithms

Contents: 1. Algorithm (Definition) 2. Computer Network (Definition)

3. Network Components (NIC, Access Point, Repeater, HUB, Bridge, Switch, Router, BRouter, GATEWAY)

4. Network Bandwidth (Definition)

5. Network Algorithms 6. Routing (Routing Protocols, Routing Table, Routing Configuration) 7. Capacity of Router 8. History of big Routers (Short History)

14

1. Algorithm (from Algoritmi, the Latin form of Al-Khwārizmī) in computer science is a step-by-step procedure for calculations, data processing, and automated reasoning to solve a specific problem.

The algorithm should be starting from an initial state and initial input, then should be transition from one state to the next to execute the instructions (which describe a computation that), eventually producing "output" and terminating at a final ending state.

initial state

exec. state

exec. state

exec. state

final state

15

2. Computer Network, often simply referred to as a network, is an interconnected collection of hardware components and autonomous computers interconnected by communication channels that allow to exchange information and share the resources.

A network consists of a set of devices like:

Hosts , host is individual computer connected to the computer network, which can offer information resources, services, and applications to users or other nodes on the network.

Nodes , node is any device that is attached to a network, either a redistribution point (capable of sending, receiving or forwarding information over a communications channel), or a communication endpoint (some terminal equipment).

16

3. Network Components are used to connect computing devices together in different networks, and to connect multiple networks or subnets together, these includes:

NIC: (Network Interface Card) is network device used to enable a network device (such as a computer or other network

equipment) to connect to a network.

Access Point: is a network device that allows wireless devices to connect to a wired network.

wired network

Access Point

Repeater

Segment A

Segment BRepeater: is a network device that connects two or more network segments and retransmits any incoming signal to all other segments.

18

HUB / Switch: is a central network device that connects all nodes in a star topology. Also it is concentrator (a device that can have multiple inputs and outputs all active at one time).

HUB Switch

Difference between

HUB and Switch

19

Bridge: is a network device that sends information between two LANs.

20

Router: is a network device that direct traffic between hosts.A router is connects two or more different networks.

BRouter: is a network device that acts as a Bridge in one circumstance and as a Router in another.

GATEWAY: The term gateway refers to a software or hardware interface that enables two different types of networked systems or software to communicate.

Network Components: NIC , Access Point , Repeater , HUB , Bridge ,

Switch , Router , BRouter , GATEWAY21

The difference between Switch and Router

Connection to other Networks

22

4. Network BandwidthNetwork Bandwidth (bit rate, channel capacity, or throughput) is a measure of communication channel usage (available or consumed of communication path) in bits/second “pbs” or multiples of it (kilobits/s “Kbps”, megabits/s “Mbps”, etc.).

23

5. Network Algorithms are the algorithms to select the paths in network along which (network traffic routes) to send network traffic “also called Routing”, and to process the network bottlenecks at servers, routers, or other networking devices.

25

There are many network algorithms like Trie based Algorithm, Multibit Trie Algorithm, etc.

6. Routing is the process of selecting paths in network along which (network traffic routes) to send network traffic.

There are two main routing protocols: • Distance-Vector (DV) Routing Protocol (Simple and efficient in

small networks and require little management, but it have count-to-infinity

problem). • Link-State (LS) Routing Protocol (More scalable for use in large

networks, but more complex).

There are other protocols like; Optimized Link State Routing Protocol (OLSR) (which used for routing mobile ad-hoc networks), and Path Vector Routing Protocol (PV) (which used for routing between

autonomous network systems).

26

Each of these routing protocols are applying a “Routing Table” to multiple routes to select the best route.

The routing table (routing metrics, or routing distances) contains information about the topology of the network immediately around the router.

The routing table consists of at least three information fields:• Network ID.• Cost (cost or length of path through).

• Next Hop (the address of the next station to which the packet is to be sent).

27

Next Hop Cost Network ID

There are two main routing configuration ways: • Static Routing: The network administrator adds the routes

(fixed paths) to the routing table manually. But when there is a change in the network or a failure occurs between two nodes, traffic will waiting for repairing the failure (not be rerouted), or the static route to be updated by the administrator before restarting its journey.

• Dynamic Routing (Adaptive Routing): The system adds routs to the routing table automatically, the adaptation is allow to rerouting the routing table when automatically.

28

Capacity of Router = N x R (measured by packets per second)

N = number of linecards (Typically 8 - 32 per chassis)R = line-rate (1Gb/s, 2.5Gb/s, 10Gb/s, 40Gb/s, 100Gb/s)

7. Capacity of Router

29

8. History of big RoutersIn the original 1960s, the general-purpose computers served as routers.

The general-purpose computers with extra hardware added to accelerate both common routing functions and specialized functions such as encryption functions.Other changes also improve reliability, such as using battery rather than mains power, and using solid storage (hard disk) rather than magnetic storage.

The first modern (dedicated, standalone) router were the Fuzzball router (with capacity: 56kbps).

30

Cisco GSR 12816Capacity: 640Gb/s

Juniper T640Capacity: 320Gb/s

31

Mikrotik 3Com

D-Link

32

Cisco Series

Cisco 2811

33

There are several manufacturers of routers including: • 3Com (www.3com.com)

• Cisco Systems (www.cisco.com)

• D-Link Systems (www.dlink.com) • Juniper Networks (www.juniper.net)

• Linksys (www.linksys.com)

• Mikrotik (www.mikrotik.com)

• NETGEAR (www.netgear.com)

34


First Class

Q & A

Principles of Network AlgorithmsSecond Semester – 2012

Prepare by: Dr. Mazin S. Aliavailable at: www.uotechnology.edu.iq/dep-cs


First Class


Lecture 2:Lookup and

Router Architecture


Lecture 2:Lookup and Router Architecture

Contents: 1. Short Review 2. Routing Table Lookup 3. Router Architecture (Input Port Processing, Switching Fabrics,

Routing Processing, Output Port Processing)

37

38

Router: (as sown in the pervious lecture) is a network device that direct traffic between hosts.A router is connects two or more different networks.

GATEWAY: The term gateway refers to a software or hardware interface that enables two different types of networked systems or software to communicate.

1. Review:

Routing Table: (Routing Metrics, or Routing Distances) contains information about the topology of the network immediately around the router, the router are applying a “Routing Table” to multiple routes to select the best route.

39

The Routing Table Lookup is search through the routing table, looking for a destination entry that best matches the destination network address of the packet, or a default route if the destination entry is missing

2. Routing Table Lookup:

The most important complicating factor is that backbone routers must operate at high speeds, being capable of performing millions of lookups per second. It is best for the input port processing to be able to proceed at line speed, that is, that a lookup can be done in less than the amount of time needed to receive a packet at the input port. In this case, input processing of a received packet can be completed before the next receive operation is complete.

3. Router Architecture A high-level view of Router Architecture is shown below.

40

Switching Fabric

Routing Processor

Input Ports Output PortsOutput ports:

Stores the packets (that

have been forwarded to it

through the switching fabric)

and then transmits the

packets on the outgoing link

Switching Fabric: Connects the

router's input ports to its output ports

Routing Processor: Executes the Routing Protocols, Maintains the Routing Tables, and performs Network

Management functions, within the router

Input Ports: Terminating an incoming

link to a router, data

link processing,

and performs a lookup and forwarding functions

3.A. Input Port ProcessingTerminating an incoming link to a router, data link processing, and performs a lookup and forwarding functions.

41

Switc

hing

Fab

ric

Line Termination

Function

Data Link Processing

Lookup, Forwarding,

Queuing

Input Port

3.A. Input Port ProcessingInside Input Port… the router determines the output port to which an arriving packet will be forwarded via the switching fabric.

42

((The choice of the output port is made using the information contained in the routing table)). A shadow copy (local copy) of the routing table is stored at each input port and updated (as needed) by the routing processor. With shadow copies (local copies) of the routing table, the switching decision can be made locally, at each input port, without invoking the centralized routing processor. Decentralized

Switching

3.A. Input Port Processing

43

When a computer works as a router; Here, the input port is just a NIC (with limited processing capabilities), so the input port simply forward the packet to the centralized routing processor (the computer's CPU) which will perform the routing table lookup and forward the packet to the appropriate output port.

As an old fashioned:

Centralized Switching

44

3.B. Switching FabricsThe switching fabric is at the heart of a router. Through it the packets are actually moved from an input port to an output port.

Switching can be accomplished in a number of ways:

45

3.B. Switching Fabrics / Switching via Memory

The input port receives the packets.

The packet was copied from the input port into memory of the routing processor (on the input port).

The routing processor extracted the destination address from the header, looked up the appropriate output port in the routing table, and copied the packet to the output port's buffers.

46

3.B. Switching Fabrics / Switching via Bus

The input ports transfer a packet directly to the output port over a shared bus, without intervention by the routing processor. But only one packet at a time can be transferred over the bus.

A packet arriving at an input port (and finding the bus busy with the transfer of another packet) is blocked from passing through the switching fabric and is queued at the input port.

Because every packet must cross the single bus, the switching bandwidth of the router is limited to the bus speed.

47

3.B. Switching Fabrics / Switching via Crossbar

One way to overcome the bandwidth limitation of a single, shared bus is to use a crossbar.A crossbar switch is an interconnection network consisting of 2N busses that connect N input ports to N output ports.

A packet arriving at an input port travels along the horizontal bus attached to the input port until it intersects with the vertical bus leading to the desired output port.

If the vertical bus is free, the packet is transferred to the output port. If the vertical bus is being used to transfer a packet from another input port to this same output port, the arriving packet is blocked and must be queued at the input port.

3.C. Routing ProcessingRouting Processing is the “Routing Table Lookup” for search through the routing table, looking for a destination entry that best matches the destination network address of the packet, or a default route if the destination entry is missing

The most important complicating factor is that backbone routers must operate at high speeds, being capable of performing millions of lookups per second, so we have several algorithms to accomplish that, like:

• Tire based Algorithm,• Multibit Tire Algorithm,• Compressed Tries,• Binary Search.

49

3.D. Output Ports ProcessingIt takes the packets which stored in the output port's memory and transmits them over the outgoing link.

The data link processing and line termination are interact with the input port on the other end of the outgoing link.

The queuing and buffer management functionality are needed when the switch fabric delivers packets to the output port at a rate that exceeds the output link rate.

Switc

hing

Fab

ric

Line Termination

Function


Queuing

Output Port


First Class

Q & A




First Class


Lecture 3:Searching Routing-Table

Algorithms



Contents: 1. Searching Algorithm (Definition)

2. Searching Routing Table (Definition)

3. Searching Routing Table Algorithms 3.1. Binary Search. 3.2. Hash Table. 3.3. Tire based Algorithms: 3.3.1. 1-Bit Trie (BMP) Algorithm 3.3.2. Multi-Bit Tire (VST) Algorithm 3.3.3. Compressed Tries 4. Tire based Algorithm for Strings

52

53

Search Algorithm: is an algorithm for finding a specific item among a collection of items.

1. Searching Algorithm:

5 3 8 2 4 6 9 1 - - - - 7 - 10

Search Example:

To find item(5) “search key” we need to only 1 step to find it,to find item(10) we need to 15 steps to find it,to find other item like item(9) we need to 7 steps to find it,and so on.

So..The best case is when we find the item at the first location (1 time),while worst case is when we find the item at the last location (n times),and the average case is (best-case + worst-case)/2.

Linear Search

“Sequential Search”

54

2. Searching Routing Table:

The most important complicating factor is that “backbone routers“ must operate at high speeds, being capable of performing millions of lookups per second.

So the lookup operations should be searching a destination through the Routing Table at high speeds.

The linear search suffered from a problem with its worst case cost, its proportional to the number of items in the list.

So the linear search is not suitable for lookups routing table, and we need to the faster searching algorithm.

55

3. Searching Routing Table Algorithms:

The worst case cost of Linear Search is proportional to the number of items in the list … this is the big problem with linear search algorithm.

Therefore, there are other algorithms will be faster, but they also impose additional requirements.

There are several Searching Algorithms to optimize the work of lookup inside routing table like:-

• Binary Search Tree• Tire based Algorithm,• Multibit Tire Algorithm,• Compressed Trie Algorithms.

56

3.1. Binary Search:

Binary Tree: is a tree that is characterized by that any node can have at most two branches. A binary may be empty or consist of a root and two disjoint binary tree called the left subtree and the right subtree .

Binary Tree Search: is a binary tree in which the left child (if there is) of any node contains a smaller value than does the parent node and the right child (if there is) contains a larger value than the parent node.

Its a fast way to search a list of items.

57

3.1. Binary Search (cont.):

The idea is to look at the item in the middle. If the key is equal to that, the search is finished. If the key is less than the middle element, do a binary search on the left half. If it's greater, do a binary search of the right half.

5

3 8

2 4 6 9

1 7 10

58

3.1. Binary Search (cont.):

The advantage of a binary search over a linear search is a very good for large-number of items.

59

3.2. Hash Table:

Hash Table: is a random access data structure (like an array), and uses a mapping function (called a hash function), to allow for O(1) searches or constant searching time.

The Hash Function provides a way for assigning numbers to the input data such that the data can then be stored at the array index corresponding to the assigned number.

60

3.2. Hash Table (cont.):

Example: We has a hash table array of strings with size=11.

Simple Hash Function hash(“ “,11) :yields

Steve

3

0

1

2

3

4

5

6

7

8

9

10

Steve

61



Steve

6

0

1

2

3

4

5

6

7

8

9

10

Spark

Spark

62



Steve

10

0

1

2

3

4

5

6

7

8

9

10

Notes

Spark

Notes

63



Steve

3

0

1

2

3

4

5

6

7

8

9

10

Pad

Spark

Notes

Pad Collision

A collision occurs when two data

items are hashed to the same value.

64


Separate chaining is a method for dealing with collisions.

The hash table is an array of linked lists.

Data items that hash to the same value are stored in a linked list originating from the index equivalent of their hash value.

0

1

2

3

4

5

6

7

8

9

10

Array of Linked Lists

65


Hash Table with Separate Chaining to avoid the collision.


0

1

2

3

4

5

6

7

8

9

10

Steve : 3

Spark : 6

Notes: 10

Pad: 3

Steve

Spark

Notes

Pad

66


A search follows the same steps as doing an insertion.i.e. the search key is “Notes”


0

1

2

3

4

5

6

7

8

9

10

Steve

Spark

Notes

Pad

Notes

10

The number of steps is O(1)

67


Separate Chaining allows us to solve the problem of collision.

The drawback is, all items inserted at the same place in the array (and this is impossible).

In that case, we'd really be doing a straight linear search on a linked list, which means that our search operation is back to being O(n) .

The worst case search time for a hash table is O(n).


First Class

Q & A




First Class


Lecture 4:Searching Routing-Table

Algorithms (Cont.)



Contents: 1. Searching Algorithm 2. Searching Routing Table 3. Searching Routing Table Algorithms 3.1. Binary Search. 3.2. Hash Table. 3.3. Tire based Algorithms: 3.3.1. 1-Bit Trie (BMP) Algorithm 3.3.2. Multi-Bit Tire (VST) Algorithm 3.3.3. Compressed Tries 4. Tire based Algorithm for Strings

70

“The term trie comes from retrieval”.

In general, a trie tree (or prefix tree), is an ordered tree data structure that is used to store a list (where the keys are usually strings).

No node in the trie tree stores the key associated with that node; instead, its position in the tree defines the key with which it is associated.

The root is associated with the empty string, and the values are normally not associated with every node, only with leaves.

3.3. Tire based Algorithms:

1-Bit Trie (or Best Matching Prefix (BMP)) is a binary tree-based data structure that uses prefix bits to direct branching, the search guided by bits.

At each level, proceed left or right based on the next address bit, on visiting a node marked as prefix, the search ends when there are no more branches to take.

The search guided by bits, these means that the sequential prefix search by length (Look at length-1 prefixes first, then length-2 prefixes, …).

Note that each step reduces the search space.

3.3. Tire based Algorithms (Cont.): 3.3.1. 1-Bit Trie Algorithm (Tire based Algorithm):

Example 1:

Prefixes: a : 0* b : 01000* c : 011* d : 1* e : 100* f : 1100* g : 1101* h : 1110* i : 1111*

3.3. Tire based Algorithms (Cont.): 3.3.1. 1-Bit Trie Algorithm(Cont.):

a

c

b

e

d

f g h i

Each step reduces the search space

Example 2:

3.3. Tire based Algorithms (Cont.): 3.3.1. 1-Bit Trie Algorithm(Cont.):

P1

P2

P3

P4

P5

P6

3.3. Tire based Algorithms (Cont.): 3.3.1. 1-Bit Trie Algorithm (Cont.):

The 1-Bit Trie algorithm is a classical solution to allow a good representation of length prefixes, but these way may involve long sequences of one-child nodes.

These requires bit inspection and these allow to increase lookup time.

drawbackhave long sequences

of one-child nodes

3.3. Tire based Algorithms (Cont.): 3.3.2. Multi-Bit Trie Algorithm (VST):

The basic idea is to speedup search by examining multiple bits at a time, for example, examine 4 bits.

The number of bits examined in each step called “Stride”, so the algorithm also called Variable-Stride Trie (VST).

Its complex algorithm to calculate, but should notes that, the nodes at the same level may have different strides.

For example; the stride for the root of some tree is 2; that for the left child of the root is 5; and that for the root’s right child is 3.

3.3. Tire based Algorithms (Cont.): 3.3.2. Multi-Bit Trie Algorithm (VST) (Cont.):

Example:

Prefixes: P1 : 10* P2 : 11* P3 : 11001* P4 : 1* P5 : 0* P6 : 1000000*

Assume that the stride for the root of some tree is 2; And that for the root’s left child is 5;And that for the root’s right child is 3.

00

01

10

11

P5

P4

P1

P200000

00001

00010

00011

11111

::

P6000

001

010

011

100

101

110

111

P3

3.3. Tire based Algorithms (Cont.): 3.3.3. Compressed Tries:

The “Compressed Tries” (or Path Compressed Tries) attempt to reduce space and time performance of the tow Trie algorithms:

• 1-Bit Trie algorithm (BMP), and • Mulit-Bit Trie algorithm.

3.3. Tire based Algorithms (Cont.): 3.3.3.A. Compressed Tries with 1-Bit Trie Algorithm:

The “Path Compressed Tries” attempt to reduce space and time performance of 1-Bit Trie algorithm (BMP), by the following: 1- Collapse one-way branch nodes. 2- Jump directly to the bit used for decision.

Prefixes: a : 0* b : 01000* c : 011* d : 1* e : 100* f : 1100* g : 1101* h : 1110* i : 1111*

a

c

b

e

d

f g h i

Collapse

Jump

a

c

b

e

d

f g h i

Collapse

Jump

a

c

b

d

f g h i

e

Collapse

Jump

a

cb

e

d

f g h i

Collapse

Jump

a

cb e

d

f g h i

a

cb e

d

f g h i

1-Bit Trie / Prefixes: a : 0* b : 01000* c : 011* d : 1* e : 100* f : 1100* g : 1101* h : 1110* i : 1111*

Compressed 1-Bit Trie/ Prefixes: a : 0* b : 01000* c : 011* d : 1* e : 100* f : 1100* g : 1101* h : 1110* i : 1111*

00*01*

10*

1-Bit Trie Prefixes: a : 0* b : 01000* c : 011* d : 1* e : 100* f : 1100* g : 1101* h : 1110* i : 1111*

1-Bit Trie Algorithm

Compressed 1-Bit Trie Algorithm

Path Compressed Tries( Collapse and Jump )

Each step reduces the search space

Compressed 1-Bit Trie Prefixes: a : 0* b : 00* c : 01* d : 1* e : 10* f : 1100* g : 1101* h : 1110* i : 1111*

3.3. Tire based Algorithms (Cont.): 3.3.3.B. Compressed Tries with Multi-Bit Trie Algorithm:

The Compression Scheme is:• Compress repeated occurrences of BMPs.• Compression is same across sub-trie.• Compression is not optimal – but access is simpler and

efficient.

Example 1: A 1-Bit Trie tree for keys "A", "to", "tea", "ted", "ten", "i", "in", and "inn“ is display here:

4. Tire based Algorithm for Strings:

A

e

it

o

a d n

n

n

Example 1 (Cont.): A Compressed tree for the 1-Bit Trie tree is display here:

A

e

it

o

a d n

n

n

Collapse

Jump

n

4. Tire based Algorithm for Strings (Cont.):


A

e

it

o

a d n

nn



A

e

it

o

a d n

nn

nn



A

e

innt

o

a d n


Example 2: Construct the 1-Bit Trie tree for the following keys: “bear", “bell", “bid", "ted", “bull", “buy", “sell", “stock", and “stop“. Then construct the Compressed 1-Bit Trie tree for it.


1-Bit Trie Tree

Compressed 1-Bit Trie Tree

Solution:

Example 3: Construct the 1-Bit Trie tree for the following keys: “yahoo", “yamal", “google", “gomee", “gomer", “facebook", “facetime", “fact", and “facetik“. Then construct the Compressed 1-Bit Trie tree for it.


Solution:

?1-Bit Trie Tree Compressed 1-Bit Trie Tree

?

Must be remember

that …

Input Links Output LinksSwitch

Forwarding Table

Processor

a

b

c

f

i

a

b

c

f

i

Prefix Output Link0 a 00 b01 c1 d10 e1100 f1101 g 1110 h 1111 i

Router



Router


Forwarding Table

Processor

a

b

c

f

i

a

b

c

f

i



1100

1100

f

Router


Forwarding Table

Processor

a

b

c

f

i

a

b

c

f

i


1100


Router


Forwarding Table

Processor

a

b

c

f

i

a

b

c

f

i


00

Decentralized Switching

Router


First Class

Q & A




First Class









104

With “1st Class - Principles of Network & Application Subject”, we have discussed the two important network reference models, the OSI reference model and the TCP/IP reference model.

1. Network Reference Models:

TCP : Transmission Control ProtocolIP : Internet Protocol

But with “1st Class - Principles of Network Algorithms Subject“, we focusing only on ‘TCP/IP Reference Model’ from Routing side of view.

TCP/IP protocol (also called IP Protocol Stack) is a set of communication protocols used for the Internet and other similar networks.

It is commonly known as TCP/IP, because of its most important protocols TCP and IP, which were the first networking protocols defined in this standard.

TCP/IP protocol have 4 layers:1. Application Layer2. Transport Layer3. Internet Layer4. Network Interface Layer

2. TCP/IP Reference Model :

HTTP FTP SMTP RTP DNS BGP RIP

Web

Browsing

Upload Files

between Devic

es

E-Mail

Multimedia

VoIP , Video

nslooku

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Router Command

Line In

terface

TCP

ICMP

UDP

IP

OSPF

ping

App

licat

ion

Laye

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Net

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Network Interface

2.1. The Application Layer:The Application Layer is a top TCP/IP layer, it’s contains all the higher-level protocols which involve user interaction, like HTTP , FTP , SMTP , RTP , DNS , BGP , RIP , and other protocols.

2. TCP/IP Reference Model (Cont.):


HTTP (Hyper Text Transfer Protocol): It’s an application

protocol for transfer hypertext,

hypermedia, over web information

systems

FTP (File Transfer Protocol):

It’s an application protocol which

provides a way to move data efficiently from

one machine to another.

SMTP (Simple Mail Transfer Protocol): It’s an application protocol for e-mail

transmission between devices.

RTP (Realtime Transport Protocol):

It’s an application protocol to

delivering audio and video over networks

DNS (Domain Name System):

It’s an application protocol to

translates domain name to IP address

BGP (Border Gateway Protocol):

It’s an application protocol to backing the core routing decisions

on the Internet

RIP (Routing Information Protocol):

It’s an application protocol to adds routs to the routing table automatically (based Distance-

Vector Routing Algorithm)


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Router Command

Line In

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Laye

r

Network CertificationRouter Command Line Interface


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Browsing

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VoIP , Video

nslooku

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BGP RIP

nslooku

pping

ICMP OSPF

Router Command

Line In

terface

DNS

The Transport Layer is located above the Internet Layer in the TCP/IP model, it’s allow peer entities on the source and destination hosts to carryon a conversation, and provides the port number.

It’s used to exchange data between systems.

2. TCP/IP Reference Model (Cont.): 2.2. The Transport Layer (Host-to-Host) (End-to-End):

There are two Transport Layer (Host-to-Host) (End-to-End) core protocols:

1. TCP (Transmission Control Protocol)2. UDP (User Datagram Protocol)


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TCP UDP

App

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TCP is a reliable connection-oriented protocol, that offers error

correction when deliver the stream originating on one machine to the

other machine in the network.

UDP is an unreliable connectionless protocol, that deliver stream

originating on one machine to the other machine in the network based one-shot philosophy.

TCP (Transmission Control Protocol) is a reliable connection-oriented protocol, that offers error correction when deliver the stream originating on one machine to the other machine in the network. It used to send important data such as webpages, database information, etc;


UDP (User Datagram Protocol) is an unreliable connectionless protocol, that deliver stream originating on one machine to the other machine in the network based one-shot philosophy. It used to send streaming audio and video (like Windows Media audio files (.WMA) , Real Player (.RM)).

The UDP is faster than TCP (UDP offers speed).


The reason UDP is faster than TCP is because there is no traffic-of ‘flow control’ or ‘error correction’ used (unreliable connectionless protocol).

The data sent over the network is affected by collisions, and errors will be present. So the TCP uses ‘flow control’ or ‘error correction’ traffic (reliable connection-oriented protocol) which need more time to finish the data sending, while UDP not doing that.

UDP is only concerned with speed. This is the main reason why streaming

media is not high quality.

The Internet Layer is located above the Transport Layer in the TCP/IP model, it’s defines an official packet format and provides the IP Addressing (using core IP Protocol), to deliver after that independently through the network between the sender and receiver.

2. TCP/IP Reference Model (Cont.): 2.3. Internet Layer:

The Internet Layer delivers “IP packets” (where they are supposed here) as is avoiding congestion.

For these reasons…The TCP/IP Internet Layer is very similar in functionality to the OSI Network Layer.

Remember that the Lecture Title is

Packet Classification


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TCP UDP

IP

App

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IP defines an official packet format and

provides IP Addresses

The Host-to-Network Layer interfaces the TCP/IP protocol stack to the physical network.

It’s a point out connect to the network using TCP/IP protocol, so it can send IP packets over it.

2. TCP/IP Reference Model (Cont.): 2.4. Network Layer (Host-To-Network) (Link):


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TCP UDP

IP

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Network Interface


First Class

Q & A




First Class



(Cont.)


Lecture 6:Packet Classification (Cont.)





122

There are another important core protocols (which works inside TCP/IP protocol) like:

• ICMP (Internet Control Message Protocol)• OSPF (Open Shortest Path First )

3. ICMP and OSPF Core Protocols:

ICMP is used by the computer operating systems to send error messages indicating, for example, that a requested service is not available or that a host or router could not be reached.

OSPF is one of group of interior routing protocols, it’s an adaptive network routing protocol which operating within a single autonomous system .


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Router Command

Line In

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TCP

ICMP

UDP

IP

OSPF

ping

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Network Interface

It’s an adaptive network routing protocol which

operating within a single autonomous system

It’s used by the computer Oss to

send error messages indicating

IP

ping

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Network Interface

Ping is a useful tool for testing, it’s dealing with ICMP to test the reachability of a host on a network and to measure the round-trip time for messages sent from the host to a destination computer.

ICMP

On any machines running Windows x, ping can be accessed via a DOS prompt. Select "Run..." from the Start menu and type command "cmd". Once you're at the DOS prompt, type "ping Host-Address".

ping yahoo.com

# ping yahoo.com PING yahoo.com (204.71.202.160): 56 data bytes 64 bytes from 204.71.202.160: icmp_seq=0 ttl=246 time=108.0 ms 64 bytes from 204.71.202.160: icmp_seq=1 ttl=246 time=102.3 ms 64 bytes from 204.71.202.160: icmp_seq=2 ttl=246 time=102.6 ms 64 bytes from 204.71.202.160: icmp_seq=3 ttl=246 time=105.5 ms 64 bytes from 204.71.202.160: icmp_seq=4 ttl=246 time=103.9 ms --- yahoo.com ping statistics --- 5 packets transmitted, 5 packets received, 0% packet loss round-trip min/avg/max = 102.3/104.4/108.0 ms

Your PC

Yahoo Server


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Router Command

Line In

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TCP

ICMP

UDP

IP

OSPF

ping

App

licat

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Laye

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port

Laye

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Net

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Network Interface

BGP RIP

Router Command

Line In

terface

OSPF

3 Well-Known Routing ProtocolsBGP , RIP , OSPF

DNS

ICMP

nslooku

pping

2 Well-Known Utility-Application Protocols

DNS , ICMP

The Internet Layer defines an official packet format (using core IP Protocol), to deliver after that independently through the network between the sender and receiver.

4. IP v4 and IP v6:

Application LayerHTTP , FTP , SMTP , RTP , DNS ,

BGP , RIP , …

Transport LayerTCP , UDP

Internet LayerIP , OSPF , ICMP , …

Network Layer

There are two types of core IP protocol, IP v4 (version 4) (32 bits) and IP v6 (version 6) (128 bits).

Internet LayerIP v4 32 bits , OSPF , ICMP , …

Internet LayerIP v6 128 bits , OSPF , ICMP , …


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Line In

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TCP

ICMP

UDP

IP

OSPF

ping

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Network Interface

IP defines an official packet format and

provides IP Addresses

There are 2 Types:IP v4 - 32bits

IP v6 - 128 bits

IP v4 Packet Format:Consists of 32 bits, so can distribute approximately 4.2 billion IPs around the world. Its developed in 1970s.

4. IP v4 and IP v6 (Cont.):

Since the 4.2 billion IPs of IPv4 will not be enough in the near future with the development and the rapid increase of users of computer, phones, gaming consoles and many other devices which connected to Internet.

This has been the development of the IPv6, which can distribute approximately 6 trillion IPs.


IP v6 Packet Format:Consists of 128 bits, so can distribute approximately 6 trillion IPs around the world. Its developed in 1993.



While IPv6 use and management is similar to IPv4, but its not backwards compatible.

It will eventually replace IPv4, but the transition could take long time to complete. Full IPv6 adoption has been slower than anticipated.

Application LayerHTTP , FTP , SMTP , RTP , DNS ,

BGP , RIP , …

Transport LayerTCP , UDP

Internet LayerIPv4 / IPv6 , OSPF , ICMP , …

Network Layer

In the meantime, all of Servers must be available over both IPv4 and IPv6, and much of Internet devices will run IPv4 and IPv6 simultaneously (this called Dual-Stack approach).

IP v6 Packet Format:

IP v4 Packet Format:X

To learn more, plz visit the following pages: - www.networkset.net/2010/05/05/ipv4-vs-ipv6/ - www.youtube.com/watch?v=-oQ4JYBjhVc&feature=related

5. TCP and UDP Packets:

TCP and UDP protocols are most communication over the Internet.

TCP Packet Format:

5. TCP and UDP Packets (Cont.):

TCP and UDP protocols are most communication over the Internet.

UDP Packet Format:

6. Simplified Network Packet Format:

In simply, each network packet consist of the 5 important parts, which used as a keys for packet classification.

DataIP Destination32 bits

IP Source32 bits

Sour. Port16 bits

Des. Port16 bitsP

roto

col

8 bi

ts

According to “Protocol Type” we can classify the packet either unreliable / reliable protocol (UDP / TCP).

According to “Des/Sou Port” we can classify the packet based on Application Layer Protocols (HTTP , FTP , SMTP , RTP , DNS , BGP , RIP , …).

According to “IP Des/Sou” we can classify the packet either IP v4/ v6, and the addressing schema.

1 2 3 4 5

7. Screening Router:

Screening Router: it’s a router that performs packet filtering to see whether a packet is part of an existing stream of traffic. Also, it can filters each packet based only on information contained in the packet itself.

Screening Router

A

B C

Each router do packet classification, when the packet addressed to it.

7. Screening Router (Cont.):

Screening Router: it’s a router that performs packet filtering to see whether a packet is part of an existing stream of traffic. Also, it can filters each packet based only on information contained in the packet itself.

Screening Router

A

B C

TO: AUDP: Video

TO: CTCP: Email

TO: BTCP: Web

TO: C

UDP: VoP

TO: AUDP: #bxsa?t^q1 In some cases a

screening router may be used as

perimeter protection for the

internal network as a filtering solution


First Class

Q & A




First Class


Lecture 7:Switching Theory and Architecture



Contents: 1. Short Reviewing 2. Switching Theory 3. Crossbar Switch Architecture 4. Crossbar Switch Models IQ Switch OQ Switch CIOQ Switch

143

1. Short Reviewing:

Switch Device: is a central network device that connects all nodes in a star topology. Also it is concentrator (a device that can have multiple inputs and outputs all active at one time).

Revi

ew

Interconnection Switching Fabric: is a fabric which connects the router's input ports to its output ports.

Revi

ew

Router - Switching can be accomplished in a number of ways (Switching via Memory , Switching via Bus , and Switching via Crossbar).Re

view


Forwarding Table

Processor

a

b

c

f

i

a

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c

f

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Router



Router


Forwarding Table

Processor

a

b

c

f

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a

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1100

1100

f

Router


Forwarding Table

Processor

a

b

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a

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1100


Router


Forwarding Table

Processor

a

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00


Router

Switch

Forwarding Table

Processor


Router

110011

11010

11001111010

1010

101100100 010100

101100

11100101010

1100111

110010 101100

110011

00011001000100

110100

1100

001100

111110

011001

01 1100111

Switch

Switching

110011

11010

1010

101100100 010100

101100

11100101010

1100111

110010 101100

110011

00011001000100

110100

1100

001100

111110

011001

01 1100111

Switch

2. Switching Theory:

Switching theory is the mathematical study of the properties of networks of idealized switches.

Switch design is mainly influenced by “Cost” and “Heat”.

Key technological factors affecting cost and heat– Memory bandwidth (not the size of memory, but its

speed)– Complexity of algorithms– Number of off-chip operations (this affects speed)

153

3. Crossbar Switch Architecture

One way to overcome the bandwidth limitation of a single, shared bus is to use a crossbar.A crossbar switch is an interconnection network consisting of 2N busses that connect N input ports to N output ports.

A packet arriving at an input port travels along the horizontal bus attached to the input port until it intersects with the vertical bus leading to the desired output port.

4. Crossbar Switch Models

There are three Crossbar Switch Models, these are: IQ Switch Model OQ Switch Model CIOQ Switch Model

155

4. Crossbar Switch Models (Cont.)

If the vertical bus is free, the packet is transferred to the output port.

If the vertical bus is being used to transfer a packet from another input port to this same output port, the arriving packet is blocked and must be queued at the input port, to enhance the performance.

Switc

hing

Fab

ric

Line Termination

Function


Lookup, Forwarding,

Input Port

Queuing

156


Switc

hing

Fab

ric

Line Termination

Function


Lookup, Forwarding,

Input Port

Queuing

If the vertical bus is free, the packet is transferred to the output port.

If the vertical bus is being used to transfer a packet from another input port to this same output port, the arriving packet is blocked and must be queued at the input port, to enhance the performance.

Input Queued (IQ) Switches

157


Also we can use the same strategy at the output port, so we can queued at the output port, to enhance the performance.

Line Termination

Function


Queuing

Output Port

Output Queued (OQ)

Switches

158


Switching Fabric

Routing Processor

Input Ports Output Ports

Queuing

IQ

Queuing

OQ

Combined Input and Output Queued (CIOQ) Crossbar Switches

4. Crossbar Switch Architecture (Cont.)

We use Combined Input and Output Queued (CIOQ) Crossbar Switches to get great performance.

When the vertical bus (in switch fabric) is being used to transfer a packet. It’s not free it’s busy. We will useful from IQ Crossbar Switch model

When the backbound network traffic was slower than the traffic on the switch fabric. We will useful from OQ Crossbar Switch model

Combined Input and Output Queued (CIOQ) Crossbar Switch Model


First Class

Q & A




First Class



and Architecture (Cont.)


Lecture 8:Switching Theory (Cont.)

Contents: 1. Review 2. Speed Up and Delay Control in CIOQ 3. Stable Marriage Algorithms for CIOQ Gale-Shapley Algorithm (GSA) 4. Scheduling Algorithms for CIOQ First In First Out Scheduling Algorithm (FIFO) Most Urgent Cell First Scheduling Algorithm (MUCF) Randomized Switch Scheduling

162


Forwarding Table

Processor

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1. Review



Router


Forwarding Table

Processor

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00


Router

2. Speed Up and Delay Control in CIOQ Switch:

The fabric speedup for an IQ switch equals 1 The fabric speedup for an OQ switch equals N

Suppose we consider switches with fabric speedup of S, so the fabric speedup for CIOQ equles 1 < S N≪

The Probabilisitc Analyses (Assume trafic model) and the Numerical Methods (Use simulated and actual traffic traces) approaches showed that switches which use a speedup of between 2 and 5 achieve the same mean delay and throughput.

1. Speed Up and Delay Control in CIOQ Switch:

The fabric speedup for an IQ switch equals 1 The fabric speedup for an OQ switch equals N

Suppose we consider switches with fabric speedup of S, so the fabric speedup for CIOQ equles 1 < S N≪

IQ CIOQ OQ

Speedup = 1Inexpensive

Poor performance

Speedup = 2--5 ?Inexpensive

Good performance

Speedup = NExpensive

Great performance

3. Stable Marriage Algorithms for CIOQ:

Most, if not all, switch scheduling algorithms use stable marriage algorithms (SMAs) like “Gale-Shapley Algorithm (GSA)”.

This is because of the following equivalence:-- request = proposal- grant and accept = engagement- final matching = marriage

3. Scheduling Algorithms for CIOQ:

The CIOQ schedule his queued work by the scheduling algorithm like:

1. Queuing the packets as packet-by-packet under a stable FIFO (First In First Out) schedule algorithm.

2. Queuing the packets based their most urgent packets under a unstable MUCF (Most Urgent Cell First) schedule algorithm.

3. Scheduling Algorithms for CIOQ:

The CIOQ schedule his queued work by the scheduling algorithm like:

1. Queuing the packets as packet-by-packet under a stable FIFO (First In First Out) schedule algorithm.

2. Queuing the packets based their most urgent packets under a unstable MUCF (Most Urgent Cell First) schedule algorithm.

3. Randomized Switch schedule algorithm, base decisions upon a small, randomly chosen sample of the inputs, instead of the complete inputs.


First Class

Q & A




First Class





Contents: 1. Review 2. Network Bandwidth 2.1. Network Bandwidth – Network Centric Approach 2.2. Network Bandwidth – User Centric Approach

173

Network Bandwidth (bit rate, channel capacity, or throughput) is a measure of communication channel usage (available or consumed of communication path) in bits/second “pbs” or multiples of it (kilobits/s “Kbps”, megabits/s “Mbps”, etc.).

174

1. Review:

175

How to congested network with many users?

2. Network Bandwidth:

The basic idea is how to congested network with many users.

So there are 2 problems will be appears:- How can allocate bandwidth fairly between the users- How can control queue size and hence delay

To solve the problems we need to partitioning the bandwidth, however we have 2 approaches, can select any one of them:- Approach 1: Network-Centric- Approach 2: User-Centric

BandwidthPartitioning

2. Network Bandwidth (Cont.):

The basic idea is how to congested network with many users.

S1

S1

S1

S1

::

D1

D1

D1

D1

D1. . . .

10Mpbs

1Mpbs

10Mpbs

2.1. Network Bandwidth – Network Centric Approach

We can divide the bandwidth depending on number of users (frequency division).

Switch

2.1. Network Bandwidth – Network Centric Approach

We can divide the bandwidth depending on number of users (frequency division).

Switch

In this approach we partitioning the bandwidth depend on the number of users.

This approach perfect fairness, but its responsive to number of users.

2.1. Network Bandwidth – User Centric Approach

We can divide the bandwidth depending on time (time division).

Switch

In this approach we partitioning the bandwidth depend on the time of packet arrival, as a FIFO.

This approach also fairness, but its responsive to congestion.


First Class

Q & A




First Class


Lecture 10:IPv4 Addressing


Lecture 10:IP Addressing

Contents: 1. IPv4 Addresses 2. Classful IPv4 Addressing Scheme 3. Public and Private IP Addresses 4. Reserved IP Addresses 5. Subnetting / Netmask 6. NAT (Network Address Translation)

183

IP Address (Internet Protocol address) is a numerical. label assigned to each device (e.g., computer, printer) participating in a computer network.

With IPv4, it's 32bits long and unique; and with IPv6, it’s 128bits long and also unique.

184

1. IPv4 Addresses:

The IPv4 Address has two parts:The Network Part(netid)(also called IP prefix) and Host Part(hostid)

to identify the host on that network

to identify the network to which host is attached

185

1. IPv4 Addresses (Cont.):

192

. 168

. 0

. 1

192

. 168

. 0

. 2

192

. 168

. 0

. 3

192

. 168

. 0

. 4

192

. 168

. 0

. 5

192 . 168 . 0 . x

192 . 168 . 0

. 0

186

1. IPv4 Addresses (Cont.):

32bits IP address divides into 4 group of 8bits.

0 8 16 24 32

2 = 8

256 (0 … 255)

0 … 255 0 … 255 0 … 255 0 … 255

To provide the flexibility to support different sized networks, with each network containing different number of hosts.

IP address space of 2 addresses was divided into three different classes for networks and hosts, as Class A, Class B, Class C, and Class D.

32

187

2. Classful IPv4 Addressing Scheme:

Classful IPv4 Addressing Scheme

188

2. Classful IPv4 Addressing Scheme (Cont.):

Classful IP Addressing Scheme

0 8 16 24 32

0 8 16 24 32

0 8 16 24 32

0 8 16 24 32

0

1 0

1 1 0

1 1 1 0

27 = 128

214= 16 384

2 21= 2 097 152

Multicast Address

2 = 16 777 21624

2 = 65 53616

2 = 2568

A host can use a , multicast address as the destination address for packet generated to indicate the packet is meant for any hosts on the Interne

Class A

Class B

Class C

Class D

189

2. Classful IPv4 Addressing Scheme (Cont.):

Classful IP Addressing Scheme0 8 16 24 32

128 16 777 216

0 8 16 24 32

16 384 65 536

0 8 16 24 32

2 097 152 256

0

1 0

1 1 0

Class A

Class B

Class C

netid hostid0

netid hostid1 0

netid hostid1 1 0

Imagine, if we had a company has 1000 Computers, It is illogical to buy 1000 IP addresses, this exploitation of the amount of IP addresses. So we can buy 1 or 2 IP addresses (as a Public IP Addresses) and distributed them (using NAT) between the computers (as a Private IP Addresses).

190

3. Public and Private IP Addresses:

Private IP Addresses

Class A

Class B

Class C

10 . 0 . 0 . 0 - 10 . 255 . 255 . 255

172 . 16 . 0 . 0 - 172 . 31 . 255 . 255

192 . 168 . 0 . 0 - 192 . 168 . 255 . 255

These addresses are commonly used for homes, offices, and enterprise LANs.

191

3. Public and Private IP Addresses (Cont.):

Private IP Addresses

Class A

Class B

Class C

10 . 0 . 0 . 0 - 10 . 255 . 255 . 255

172 . 16 . 0 . 0 - 172 . 31 . 255 . 255

192 . 168 . 0 . 0 - 192 . 168 . 255 . 255

Just for speed observation (for Private or Public IP Addresses):each class started with specific range as shown

Class A : 1 - 126Class B: 128 - 190Class C: 191 - 223 192.168.0.3

Class C

There are certain IP addresses are reserved by the IANA for special use.

192

4. Reserved IP Addresses:

Reserved for IP broadcast messages to the

current network 0 . 0 . 0 . 0- 0 . 255.255.255

the "limited broadcast" destination address

255.255.255.255

loopback addresses to the local host (troubleshooting)

127.0.0.0- 127.255.255.255

Network ID Host : All 0’s

broadcast Host: All 255’s

future use Started 224 - 255

A Subnet is a logically subdivision of an IP network. The practice of dividing a network into two or more networks is called Subnetting.

193

5. Subnetting / Netmask:

For example:192 . 168 . 40 . 3

Class C

255 . 255 . 255 . 0

11000000 10101000 00101000 00000011

11 111111 11111 111 111111 11 00000000

11000000 10101000 00101000 00000000AND

192 . 168 . 40 . 0

IP Address

Subnet Mask (/24)

Gateway

194

5. Subnetting / Netmask (Cont.):

10 . 0 . 0 . 2

Class A

255 . 0 . 0 . 0

AND

10 . 0 . 0 . 0

IP Address

Subnet Mask (/8)

Gateway

NAT (Network Address Translation) is the process of modifying IP address information in IP packet headers while in transit across a traffic routing device.

It’s use to translate the Private IP to Public IP and vice versa.

195

6. NAT (Network Address Translation):

yahoo.com

192.168.0.7

Public IP Request Private IP

: : :68.143.77.1

5yahoo.com 192.168.0.7

: : :

68.143.77.15

NAT

There are three types of NAT: 1- Static NAT 2- Dynamic NAT 3- Overloading NAT

196

6. NAT (Network Address Translation) (Cont.):

68.143.77.1568.143.77.1668.143.77.17

192.168.0.7


First Class

Q & A



university of technology computer science department network administration branch first class

Documents

routing table algorithms

network link

network layer host

network bandwidth definition

routing routing protocols

routing table definition

network reference models

algorithm definition