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Computer Networks NYUS FCSIT Spring 2008 Milos STOLIC, Bs.C. Teaching Assistant [email protected]
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Computer Networks

Jan 07, 2016

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Computer Networks. NYUS FCSIT Spring 2008 Milos STOLIC, Bs.C. Teaching Assistant [email protected]. The Network Layer. Chapter 5. Network Layer Design Isues. Store-and-Forward Packet Switching Services Provided to the Transport Layer Implementation of Connectionless Service - PowerPoint PPT Presentation
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Page 1: Computer Networks

Computer Networks

NYUS FCSITSpring 2008

Milos STOLIC, Bs.C.Teaching Assistant

[email protected]

Page 2: Computer Networks

The Network Layer

Chapter 5

Page 3: Computer Networks

Network Layer Design Isues

a) Store-and-Forward Packet Switching

b) Services Provided to the Transport Layer

c) Implementation of Connectionless Service

d) Implementation of Connection-Oriented Service

e) Comparison of Virtual-Circuit and Datagram Subnets

Page 4: Computer Networks

Store-and-Forward Packet Switching

The environment of the network layer protocols.

fig 5-1

Page 5: Computer Networks

Implementation of Connectionless Service

Routing within a diagram subnet.

Page 6: Computer Networks

Implementation of Connection-Oriented Service

Routing within a virtual-circuit subnet.

Page 7: Computer Networks

Comparison of Virtual-Circuit and Datagram Subnets

5-4

Page 8: Computer Networks

Routing Algorithms

a) The Optimality Principle

b) Shortest Path Routing

c) Flooding

d) Distance Vector Routing

e) Link State Routing

f) Hierarchical Routing

g) Broadcast Routing

h) Multicast Routing

i) Routing for Mobile Hosts

Page 9: Computer Networks

Routing Algorithms (2)

Conflict between fairness and optimality.

Page 10: Computer Networks

The Optimality Principle

(a) A subnet. (b) A sink tree for router B.

Page 11: Computer Networks

Shortest Path Routing

The first 5 steps used in computing the shortest path from A to D. The arrows indicate the working node.

Page 12: Computer Networks

Flooding

Dijkstra's algorithm to compute the shortest path through a graph.

5-8 top

Page 13: Computer Networks

Flooding (2)

Dijkstra's algorithm to compute the shortest path through a graph.

5-8 bottom

Page 14: Computer Networks

Distance Vector Routing

(a) A subnet. (b) Input from A, I, H, K, and the new routing table for J.

Page 15: Computer Networks

Distance Vector Routing (2)

The count-to-infinity problem.

Page 16: Computer Networks

Link State Routing

Each router must do the following:

A. Discover its neighbors, learn their network address.

B. Measure the delay or cost to each of its neighbors.

C. Construct a packet telling all it has just learned.

D. Send this packet to all other routers.

E. Compute the shortest path to every other router.

Page 17: Computer Networks

Learning about the Neighbors

(a) Nine routers and a LAN. (b) A graph model of (a).

Page 18: Computer Networks

Measuring Line Cost

A subnet in which the East and West parts are connected by two lines.

Page 19: Computer Networks

Building Link State Packets

(a) A subnet. (b) The link state packets for this subnet.

Page 20: Computer Networks

Distributing the Link State Packets

The packet buffer for router B in the previous slide (Fig. 5-13).

Page 21: Computer Networks

Hierarchical Routing

Hierarchical routing.

Page 22: Computer Networks

Broadcast Routing

Reverse path forwarding. (a) A subnet. (b) a Sink tree. (c) The tree built by reverse path forwarding.

Page 23: Computer Networks

Multicast Routing

(a) A network. (b) A spanning tree for the leftmost router. (c) A multicast tree for group 1. (d) A multicast tree for group 2.

Page 24: Computer Networks

Routing for Mobile Hosts

A WAN to which LANs, MANs, and wireless cells are attached.

Page 25: Computer Networks

Routing for Mobile Hosts (2)

Packet routing for mobile users.

Page 26: Computer Networks

Congestion Control Algorithms

a) General Principles of Congestion Control

b) Congestion Prevention Policies

c) Congestion Control in Virtual-Circuit Subnets

d) Congestion Control in Datagram Subnets

e) Load Shedding

f) Jitter Control

Page 27: Computer Networks

Congestion

When too much traffic is offered, congestion sets in and performance degrades sharply.

Page 28: Computer Networks

General Principles of Congestion Control

A. Monitor the system .

– detect when and where congestion occurs.

B. Pass information to where action can be taken.

C. Adjust system operation to correct the problem.

Page 29: Computer Networks

Congestion Prevention Policies

Policies that affect congestion.

5-26

Page 30: Computer Networks

Congestion Control in Virtual-Circuit Subnets

(a) A congested subnet. (b) A redrawn subnet, eliminates congestion and a virtual circuit from A to B.

Page 31: Computer Networks

Hop-by-Hop Choke Packets

(a) A choke packet that affects only the source.

(b) A choke packet that affects each hop it passes through.

Page 32: Computer Networks

Jitter Control

(a) High jitter. (b) Low jitter.

Page 33: Computer Networks

Quality of Service

a) Requirements

b) Techniques for Achieving Good Quality of Service

Page 34: Computer Networks

Requirements

How stringent the quality-of-service requirements are.

5-30

Page 35: Computer Networks

Buffering

Smoothing the output stream by buffering packets.

Page 36: Computer Networks

The Leaky Bucket Algorithm

(a) A leaky bucket with water. (b) a leaky bucket with packets.

Page 37: Computer Networks

The Leaky Bucket

Algorithm

(a) Input to a leaky bucket. (b) Output from a leaky bucket. Output from a token bucket with capacities of (c) 250 KB, (d) 500 KB, (e) 750 KB, (f) Output from a 500KB token bucket feeding a 10-MB/sec leaky bucket.

Page 38: Computer Networks

The Token Bucket Algorithm

(a) Before. (b) After.

5-34

Page 39: Computer Networks

Admission Control

An example of flow specification.

5-34

Page 40: Computer Networks

Packet Scheduling

(a) A router with five packets queued for line O.(b) Finishing times for the five packets.

Page 41: Computer Networks

Internetworking

a) How Networks Differ

b) How Networks Can Be Connected

c) Concatenated Virtual Circuits

d) Connectionless Internetworking

e) Tunneling

f) Internetwork Routing

g) Fragmentation

Page 42: Computer Networks

Connecting Networks

A collection of interconnected networks.

Page 43: Computer Networks

How Networks Differ

Some of the many ways networks can differ.

5-43

Page 44: Computer Networks

How Networks Can Be Connected

(a) Two Ethernets connected by a switch. (b) Two Ethernets connected by routers.

Page 45: Computer Networks

Concatenated Virtual Circuits

Internetworking using concatenated virtual circuits.

Page 46: Computer Networks

Connectionless Internetworking

A connectionless internet.

Page 47: Computer Networks

Tunneling

Tunneling a packet from Paris to London.

Page 48: Computer Networks

Tunneling (2)

Tunneling a car from France to England.

Page 49: Computer Networks

Internetwork Routing

(a) An internetwork. (b) A graph of the internetwork.

Page 50: Computer Networks

Fragmentation

(a) Transparent fragmentation. (b) Nontransparent fragmentation.

Page 51: Computer Networks

Fragmentation (2)

Fragmentation when the elementary data size is 1 byte.(a) Original packet, containing 10 data bytes.(b) Fragments after passing through a network with maximum

packet size of 8 payload bytes plus header.(c) Fragments after passing through a size 5 gateway.

Page 52: Computer Networks

The Network Layer in the Internet

a) The IP Protocol

b) IP Addresses

c) Internet Control Protocols

d) IPv6

Page 53: Computer Networks

Design Principles for Internet

A. Make sure it works.

B. Keep it simple.

C. Make clear choices.

D. Exploit modularity.

E. Expect heterogeneity.

F. Avoid static options and parameters.

G. Look for a good design; it need not be perfect.

H. Be strict when sending and tolerant when receiving.

I. Think about scalability.

J. Consider performance and cost.

Page 54: Computer Networks

Collection of Subnetworks

The Internet is an interconnected collection of many networks.

Page 55: Computer Networks

The IP Protocol

The IPv4 (Internet Protocol) header.

Page 56: Computer Networks

The IP Protocol (2)

Some of the IP options.

5-54

Page 57: Computer Networks

IP Addresses

IP address formats.

Page 58: Computer Networks

IP Addresses (2)

Special IP addresses.

Page 59: Computer Networks

Subnets

A campus network consisting of LANs for various departments.

Page 60: Computer Networks

Subnets (2)

A class B network subnetted into 64 subnets.

Page 61: Computer Networks

CDR – Classless InterDomain Routing

A set of IP address assignments.

5-59

Page 62: Computer Networks

Internet Control Message Protocol

The principal ICMP message types.

5-61

Page 63: Computer Networks

ARP– The Address Resolution Protocol

Three interconnected /24 networks: two Ethernets and an FDDI ring.

Page 64: Computer Networks

Dynamic Host Configuration Protocol

Operation of DHCP.

Page 65: Computer Networks

The Main IPv6 Header

The IPv6 fixed header (required).

Page 66: Computer Networks

Extension Headers

IPv6 extension headers.

5-69

Page 67: Computer Networks

Extension Headers (2)

The hop-by-hop extension header for large datagrams (jumbograms).

Page 68: Computer Networks

Extension Headers (3)

The extension header for routing.