Presentation is loading. Please wait.

Presentation is loading. Please wait.

Introduction 1-1 1DT066 Distributed Information System Chapter 4 Network Layer.

Published byChaya Blachly Modified over 9 years ago

Similar presentations

Presentation on theme: "Introduction 1-1 1DT066 Distributed Information System Chapter 4 Network Layer."— Presentation transcript:

1 Introduction 1-1 1DT066 Distributed Information System Chapter 4 Network Layer

2 C HAPTER 4: N ETWORK L AYER Chapter goals: understand principles behind network layer services: network layer service models forwarding versus routing how a router works routing (path selection) dealing with scale advanced topics: IPv6, mobility instantiation, implementation in the Internet 4-2 Network Layer

3 C HAPTER 4: N ETWORK L AYER Network Layer 4-3 4. 1 Introduction 4.2 Virtual circuit and datagram networks 4.3 What’s inside a router 4.4 IP: Internet Protocol Datagram format IPv4 addressing IPv6

4 N ETWORK LAYER Network Layer 4-4 transport segment from sending to receiving host on sending side encapsulates segments into datagrams on receiver side, delivers segments to transport layer network layer protocols in every host, router router examines header fields in all IP datagrams passing through it application transport network data link physical application transport network data link physical network data link physical network data link physical network data link physical network data link physical network data link physical network data link physical network data link physical network data link physical network data link physical network data link physical network data link physical

5 T WO K EY N ETWORK -L AYER F UNCTIONS forwarding: move packets from router’s input to appropriate router output routing: determine route taken by packets from source to dest. routing algorithms 4-5 Network Layer analogy: r routing: process of planning trip from source to dest r forwarding: process of getting through single interchange

6 Network Layer 4-6 1 2 3 0111 value in arriving packet’s header routing algorithm local forwarding table header value output link 0100 0101 0111 1001 32213221 Interplay between routing and forwarding

7 C HAPTER 4: N ETWORK L AYER Network Layer 4-7 4. 1 Introduction 4.2 Virtual circuit and datagram networks 4.3 What’s inside a router 4.4 IP: Internet Protocol Datagram format IPv4 addressing ICMP IPv6

8 N ETWORK LAYER CONNECTION AND CONNECTION - LESS SERVICE datagram network provides network-layer connectionless service VC network provides network-layer connection service 4-8 Network Layer

9 V IRTUAL CIRCUITS Network Layer 4-9 each packet carries VC identifier (not destination host address) every router on source-dest path maintains “state” for each passing connection link, router resources (bandwidth, buffers) may be allocated to VC (dedicated resources = predictable service) “source-to-dest path behaves much like telephone circuit” performance-wise network actions along source-to-dest path

10 F ORWARDING TABLE 4- 10 Network Layer 12 22 32 1 2 3 VC number interface number Incoming interface Incoming VC # Outgoing interface Outgoing VC # 1 12 3 22 2 63 1 18 3 7 2 17 1 97 3 87 … … Forwarding table in northwest router: Routers maintain connection state information!

11 VIRTUAL CIRCUITS: SIGNALING PROTOCOLS Network Layer 4- 11 used in ATM, frame-relay, X.25 not used in today’s Internet application transport network data link physical application transport network data link physical 1. Initiate call 2. incoming call 3. Accept call 4. Call connected 5. Data flow begins 6. Receive data

12 DATAGRAM NETWORKS Network Layer 4- 12 no call setup at network layer routers: no state about end-to-end connections no network-level concept of “connection” packets forwarded using destination host address packets between same source-dest pair may take different paths application transport network data link physical application transport network data link physical 1. Send data 2. Receive data

13 F ORWARDING TABLE 4- 13 Network Layer Destination Address Range Link Interface 11001000 00010111 00010000 00000000 through 0 11001000 00010111 00010111 11111111 11001000 00010111 00011000 00000000 through 1 11001000 00010111 00011000 11111111 11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111 otherwise 3 4 billion possible entries

14 L ONGEST PREFIX MATCHING 4- 14 Network Layer Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3 DA: 11001000 00010111 00011000 10101010 Examples DA: 11001000 00010111 00010110 10100001 Which interface?

15 C HAPTER 4: N ETWORK L AYER Network Layer 4- 15 4. 1 Introduction 4.2 Virtual circuit and datagram networks 4.3 What’s inside a router 4.4 IP: Internet Protocol Datagram format IPv4 addressing IPv6

16 ROUTER ARCHITECTURE OVERVIEW Two key router functions: run routing algorithms/protocol (RIP, OSPF, BGP) forwarding datagrams from incoming to outgoing link 4- 16 Network Layer

17 C HAPTER 4: N ETWORK L AYER Network Layer 4- 17 4. 1 Introduction 4.2 Virtual circuit and datagram networks 4.3 What’s inside a router 4.4 IP: Internet Protocol Datagram format IPv4 addressing IPv6

18 THE INTERNET NETWORK LAYER Network Layer 4- 18 Host, router network layer functions: forwarding table Routing protocols path selection RIP, OSPF, BGP IP protocol addressing conventions datagram format packet handling conventions ICMP protocol error reporting router “signaling” Transport layer: TCP, UDP Link layer physical layer Network layer

19 C HAPTER 4: N ETWORK L AYER Network Layer 4- 19 4. 1 Introduction 4.2 Virtual circuit and datagram networks 4.3 What’s inside a router 4.4 IP: Internet Protocol Datagram format IPv4 addressing IPv6

20 IP DATAGRAM FORMAT 4- 20 Network Layer ver length 32 bits data (variable length, typically a TCP or UDP segment) 16-bit identifier header checksum time to live 32 bit source IP address IP protocol version number header length (bytes) max number remaining hops (decremented at each router) for fragmentation/ reassembly total datagram length (bytes) upper layer protocol to deliver payload to head. len type of service “type” of data flgs fragment offset upper layer 32 bit destination IP address Options (if any)

21 IP FRAGMENTATION & REASSEMBLY 4- 21 network links have MTU (max.transfer size) largest possible link-level frame. large IP datagram divided (“fragmented”) within net one datagram becomes several datagrams “reassembled” only at final destination IP header bits used to identify, order related fragments fragmentation: in: one large datagram out: 3 smaller datagrams reassembly

22 IP FRAGMENTATION AND REASSEMBLY Network Layer 4- 22 ID =x offset =0 fragflag =0 length =4000 ID =x offset =0 fragflag =1 length =1500 ID =x offset =185 fragflag =1 length =1500 ID =x offset =370 fragflag =0 length =1040 One large datagram becomes several smaller datagrams Example r 4000 byte datagram r MTU = 1500 bytes 1480 bytes in data field offset = 1480/8

23 C HAPTER 4: N ETWORK L AYER Network Layer 4- 23 4. 1 Introduction 4.2 Virtual circuit and datagram networks 4.3 What’s inside a router 4.4 IP: Internet Protocol Datagram format IPv4 addressing IPv6

24 IP ADDRESSING: INTRODUCTION Network Layer 4- 24 IP address: 32-bit identifier for host, router interface interface: connection between host/router and physical link router’s typically have multiple interfaces host typically has one interface IP addresses associated with each interface 223.1.1.1 223.1.1.2 223.1.1.3 223.1.1.4 223.1.2.9 223.1.2.2 223.1.2.1 223.1.3.2 223.1.3.1 223.1.3.27 223.1.1.1 = 11011111 00000001 00000001 00000001 223 111

25 S UBNETS Network Layer 4- 25 IP address: subnet part (high order bits) host part (low order bits) What’s a subnet ? device interfaces with same subnet part of IP address can physically reach each other without intervening router 223.1.1.1 223.1.1.2 223.1.1.3 223.1.1.4 223.1.2.9 223.1.2.2 223.1.2.1 223.1.3.2 223.1.3.1 223.1.3.27 network consisting of 3 subnets subnet

26 S UBNETS Network Layer 4- 26 To determine the subnets, detach each interface from its host or router, creating islands of isolated networks. Each isolated network is called a subnet. 223.1.1.0/24 223.1.2.0/24 223.1.3.0/24 Subnet mask: /24

27 S UBNETS Network Layer 4- 27 How many? 223.1.1.1 223.1.1.3 223.1.1.4 223.1.2.2 223.1.2.1 223.1.2.6 223.1.3.2 223.1.3.1 223.1.3.27 223.1.1.2 223.1.7.0 223.1.7.1 223.1.8.0223.1.8.1 223.1.9.1 223.1.9.2

28 IP ADDRESSING : CIDR CIDR: Classless InterDomain Routing subnet portion of address of arbitrary length address format: a.b.c.d/x, where x is # bits in subnet portion of address 4- 28 Network Layer 11001000 00010111 00010000 00000000 subnet part host part 200.23.16.0/23

29 IP ADDRESSES: HOW TO GET ONE? Q: How does a host get IP address? hard-coded by system admin in a file Windows: control-panel->network->configuration->tcp/ip- >properties UNIX: /etc/rc.config DHCP: Dynamic Host Configuration Protocol: dynamically get address from as server “plug-and-play” 4- 29 Network Layer

30 DHCP: D YNAMIC H OST C ONFIGURATION P ROTOCOL Goal: allow host to dynamically obtain its IP address from network server when it joins network Allows reuse of addresses 4- 30 Network Layer 223.1.1.1 223.1.1.2 223.1.1.3 223.1.1.4 223.1.2.9 223.1.2.2 223.1.2.1 223.1.3.2 223.1.3.1 223.1.3.27 A B E DHCP server arriving DHCP client needs address in this network

31 DHCP CLIENT - SERVER SCENARIO 4- 31 Network Layer DHCP server: 223.1.2.5 arriving client time DHCP discover src : 0.0.0.0, 68 dest.: 255.255.255.255,67 yiaddr: 0.0.0.0 transaction ID: 654 DHCP offer src: 223.1.2.5, 67 dest: 255.255.255.255, 68 yiaddrr: 223.1.2.4 transaction ID: 654 Lifetime: 3600 secs DHCP request src: 0.0.0.0, 68 dest:: 255.255.255.255, 67 yiaddrr: 223.1.2.4 transaction ID: 655 Lifetime: 3600 secs DHCP ACK src: 223.1.2.5, 67 dest: 255.255.255.255, 68 yiaddrr: 223.1.2.4 transaction ID: 655 Lifetime: 3600 secs

32 IP ADDRESSES: HOW TO GET ONE? Q: How does network get subnet part of IP addr? A: gets allocated portion of its provider ISP’s address space ISP's block 11001000 00010111 00010000 00000000 200.23.16.0/20 4- 32 Network Layer Organization 0 11001000 00010111 00010000 00000000 200.23.16.0/23 Organization 1 11001000 00010111 00010010 00000000 200.23.18.0/23 Organization 2 11001000 00010111 00010100 00000000 200.23.20.0/23... ….. …. …. Organization 7 11001000 00010111 00011110 00000000 200.23.30.0/23

33 HIERARCHICAL ADDRESSING: ROUTE AGGREGATION 4- 33 Network Layer “Send me anything with addresses beginning 200.23.16.0/20” 200.23.16.0/23200.23.18.0/23200.23.30.0/23 Fly-By-Night-ISP Organization 0 Organization 7 Internet Organization 1 ISPs-R-Us “Send me anything with addresses beginning 199.31.0.0/16” 200.23.20.0/23 Organization 2...... Hierarchical addressing allows efficient advertisement of routing information:

34 NAT: N ETWORK A DDRESS T RANSLATION 4- 34 10.0.0.1 10.0.0.2 10.0.0.3 10.0.0.4 138.76.29.7 local network (e.g., home network) 10.0.0/24 rest of Internet Datagrams with source or destination in this network have 10.0.0/24 address for source, destination (as usual) All datagrams leaving local network have same single source NAT IP address: 138.76.29.7, different source port numbers

35 NAT: N ETWORK A DDRESS T RANSLATION Motivation: local network uses just one IP address as far as outside world is concerned: range of addresses not needed from ISP: just one IP address for all devices can change addresses of devices in local network without notifying outside world can change ISP without changing addresses of devices in local network devices inside local net not explicitly addressable, visible by outside world (a security plus). 4- 35 Network Layer

36 NAT: N ETWORK A DDRESS T RANSLATION Implementation: NAT router must: outgoing datagrams: replace (source IP address, port #) of every outgoing datagram to (NAT IP address, new port #)... remote clients/servers will respond using (NAT IP address, new port #) as destination addr. remember (in NAT translation table) every (source IP address, port #) to (NAT IP address, new port #) translation pair incoming datagrams: replace (NAT IP address, new port #) in dest fields of every incoming datagram with corresponding (source IP address, port #) stored in NAT table 4- 36 Network Layer

37 NAT: N ETWORK A DDRESS T RANSLATION Network Layer 4- 37 10.0.0.1 10.0.0.2 10.0.0.3 S: 10.0.0.1, 3345 D: 128.119.40.186, 80 1 10.0.0.4 138.76.29.7 1: host 10.0.0.1 sends datagram to 128.119.40.186, 80 NAT translation table WAN side addr LAN side addr 138.76.29.7, 5001 10.0.0.1, 3345 …… S: 128.119.40.186, 80 D: 10.0.0.1, 3345 4 S: 138.76.29.7, 5001 D: 128.119.40.186, 80 2 2: NAT router changes datagram source addr from 10.0.0.1, 3345 to 138.76.29.7, 5001, updates table S: 128.119.40.186, 80 D: 138.76.29.7, 5001 3 3: Reply arrives dest. address: 138.76.29.7, 5001 4: NAT router changes datagram dest addr from 138.76.29.7, 5001 to 10.0.0.1, 3345

38 C HAPTER 4: N ETWORK L AYER Network Layer 4- 38 4. 1 Introduction 4.2 Virtual circuit and datagram networks 4.3 What’s inside a router 4.4 IP: Internet Protocol Datagram format IPv4 addressing IPv6

39 IP V 6 Initial motivation: 32-bit address space soon to be completely allocated. Additional motivation: header format helps speed processing/forwarding header changes to facilitate QoS IPv6 datagram format: fixed-length 40 byte header no fragmentation allowed 4- 39 Network Layer

40 IP V 6 H EADER (C ONT ) 4- 40 Network Layer Priority: identify priority among datagrams in flow Flow Label: identify datagrams in same “flow.” (concept of“flow” not well defined). Next header: identify upper layer protocol for data

41 C HAPTER 4: SUMMARY Network Layer 4- 41 4. 1 Introduction 4.2 Virtual circuit and datagram networks 4.3 What’s inside a router 4.4 IP: Internet Protocol Datagram format IPv4 addressing IPv6 4.5 Routing algorithms Link state Distance Vector Hierarchical routing 4.6 Routing in the Internet RIP OSPF BGP 4.7 Broadcast and multicast routing

Download ppt "Introduction 1-1 1DT066 Distributed Information System Chapter 4 Network Layer."

Similar presentations

CPSC 441 - Network Layer4-1 IP addresses: how to get one? Q: How does a host get IP address? r hard-coded by system admin in a file m Windows: control-panel->network->configuration-

CPSC Network Layer4-1 IP addresses: how to get one? Q: How does a host get IP address? r hard-coded by system admin in a file m Windows: control-panel->network->configuration-
CS 457 – Lecture 16 Global Internet - BGP Spring 2012.

CS 457 – Lecture 16 Global Internet - BGP Spring 2012.
4: Network Layer4a-1 IP Addressing: introduction r IP address: 32-bit identifier for host, router interface r interface: connection between host, router.

4: Network Layer4a-1 IP Addressing: introduction r IP address: 32-bit identifier for host, router interface r interface: connection between host, router.
8-1 Last time □ Network layer ♦ Introduction forwarding vs. routing ♦ Virtual circuit vs. datagram details connection setup, teardown VC# switching forwarding.

8-1 Last time □ Network layer ♦ Introduction forwarding vs. routing ♦ Virtual circuit vs. datagram details connection setup, teardown VC# switching forwarding.
Announcement r Recitation tomorrow on Project 2 r Midterm Survey at the end of this class.

Announcement r Recitation tomorrow on Project 2 r Midterm Survey at the end of this class.
Week 5: Internet Protocol Continue to discuss Ethernet and ARP –MTU –Ethernet and ARP packet format IP: Internet Protocol –Datagram format –IPv4 addressing.

Week 5: Internet Protocol Continue to discuss Ethernet and ARP –MTU –Ethernet and ARP packet format IP: Internet Protocol –Datagram format –IPv4 addressing.
Introduction 1-1 1DT014/1TT821 Computer Networks I Chapter 4 Network Layer.

Introduction 1-1 1DT014/1TT821 Computer Networks I Chapter 4 Network Layer.
Network Layer 4-1 4.1 introduction 4.2 virtual circuit and datagram networks 4.3 what’s inside a router 4.4 IP: Internet Protocol  datagram format  IPv4.

Network Layer introduction 4.2 virtual circuit and datagram networks 4.3 what’s inside a router 4.4 IP: Internet Protocol  datagram format  IPv4.
Network Layer4-1 Computer Networking (Datakom) Chapter 4: Network Layer Chapter goals: r understand principles behind network layer services: m routing.

Network Layer4-1 Computer Networking (Datakom) Chapter 4: Network Layer Chapter goals: r understand principles behind network layer services: m routing.
Chapter 5 The Network Layer.

Chapter 5 The Network Layer.
N/W Layer Addressing1 Instructor: Anirban Mahanti Office: ICT 745 Class Location: ICT 121 Lectures: MWF 12:00 – 12:50 Notes.

N/W Layer Addressing1 Instructor: Anirban Mahanti Office: ICT Class Location: ICT 121 Lectures: MWF 12:00 – 12:50 Notes.
Chapter 4 Network Layer slides are modified from J. Kurose & K. Ross CPE 400 / 600 Computer Communication Networks Lecture 14.

Chapter 4 Network Layer slides are modified from J. Kurose & K. Ross CPE 400 / 600 Computer Communication Networks Lecture 14.
Network Layer Overview and IP

Network Layer Overview and IP
11- IP Network Layer4-1. Network Layer4-2 The Internet Network layer forwarding table Host, router network layer functions: Routing protocols path selection.

11- IP Network Layer4-1. Network Layer4-2 The Internet Network layer forwarding table Host, router network layer functions: Routing protocols path selection.
Network Layer4-1 IP: Internet Protocol r Datagram format r IPv4 addressing r DHCP: Dynamic Host Configuration Protocol r NAT: Network Address Translation.

Network Layer4-1 IP: Internet Protocol r Datagram format r IPv4 addressing r DHCP: Dynamic Host Configuration Protocol r NAT: Network Address Translation.
Network Layer4-1 Chapter 4 Network Layer Computer Networking: A Top Down Approach Featuring the Internet, 3 rd edition. Jim Kurose, Keith Ross Addison-Wesley,

Network Layer4-1 Chapter 4 Network Layer Computer Networking: A Top Down Approach Featuring the Internet, 3 rd edition. Jim Kurose, Keith Ross Addison-Wesley,
Network Layer4-1 Data Communication and Networks Lecture 6 Networks: Part 1 Circuit Switching, Packet Switching, The Network Layer October 13, 2005.

Network Layer4-1 Data Communication and Networks Lecture 6 Networks: Part 1 Circuit Switching, Packet Switching, The Network Layer October 13, 2005.
Network Layer4-1 2010 session 1 TELE3118: Network Technologies Week 4: Network Layer Basics, Addressing Some slides have been taken from: r Computer Networking:

Network Layer session 1 TELE3118: Network Technologies Week 4: Network Layer Basics, Addressing Some slides have been taken from: r Computer Networking:
Network Layer4-1 Network layer r transport segment from sending to receiving host r on sending side encapsulates segments into datagrams r on rcving side,

Network Layer4-1 Network layer r transport segment from sending to receiving host r on sending side encapsulates segments into datagrams r on rcving side,
Network Layer4-1 Network layer r transport segment from sending to receiving host r on sending side encapsulates segments into datagrams r on rcving side,

Network Layer4-1 Network layer r transport segment from sending to receiving host r on sending side encapsulates segments into datagrams r on rcving side,

Similar presentations

Ads by Google