iLab Basics Benjamin Hof hof@in.tum.de Lehrstuhl fr - PowerPoint PPT Presentation

iLab Basics Benjamin Hof hof@in.tum.de Lehrstuhl für Netzarchitekturen und Netzdienste Fakultät für Informatik Technische Universität München Lab 1 – 15ss 1

Outline Internet protocol architecture MAC addresses Internet protocol L3 address resolution 2

Outline Internet protocol architecture MAC addresses Internet protocol L3 address resolution 3

Layer model ISO/OSI concept Internet example protocols 7. application 6. presentation application DNS, DHCP, HTTP 5. session 4. transport transport TCP, UDP, SCTP 3. network network IPv6, ICMP, IPSec 2. data link link Ethernet, WLAN 1. physical 4

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Example: HTTP communication in a local area network HTTP protocol browser HTTP server TCP protocol TCP TCP IP protocol IP IP Ethernet protocol Ethernet driver Ethernet driver Ethernet 6

Example: two networks connected with a router HTTP protocol browser HTTP server TCP protocol TCP TCP router IP protocol IP protocol IP IP IP Ethernet WLAN Ethernet Ethernet WLAN WLAN driver protocol driver driver protocol driver wireless LAN Ethernet 7

Encapsulation of data in the protocol stack user data application user data header application data TCP header segment application data IP header TCP header packet/datagram Ethernet Ethernet application data IP header TCP header header trailer frame 8

Terminology network layer SDU IP header network layer PDU Ethernet Ethernet data link layer SDU header trailer data link layer PDU ◮ Protocol Data Unit ◮ Sercie Data Unit ◮ Interface: service access point (SAP) 9

Design decisions ◮ no state between sender and destination ◮ end-to-end principle ◮ separation of packet forwarding and routing 10

Outline Internet protocol architecture MAC addresses Internet protocol L3 address resolution 11

Layer 2 addresses/frame ◮ MAC addresses, “physical address” ◮ specific for medium ◮ Ethernet/WLAN: 48 bit ◮ vendor and product information ◮ not hierarchical Why are MAC addresses not used for addressing devices on the Internet? 12

Ethernet layer 2 0 15 16 31 destination address source address type      service data unit      ❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤    46-1500 ❤  ❤ ❤ ❤ ❤ ❤ ❤ octets ❤ ❤ ❤ ❤ ❤  ❤ ❤  ❤  ❤ ❤  ❤ ❤  ❤ ❤  ❤ ❤  ❤  ❤ ❤  ❤ ❤  . . .    frame check sequence 13

Layer 2 traffic switch PC 0 PC 1 A B C PC 2 PC 0 transmits: 1. destination MAC PC 1 2. destination MAC FF:FF:FF:FF:FF:FF 14

Outline Internet protocol architecture MAC addresses Internet protocol L3 address resolution 15

Internet Protocol ◮ packet switched ◮ best effort ◮ connectionless ◮ unreliable ◮ no flow control 16

IPv6 header 0 3 4 11 12 15 16 23 24 31 version traffic class flow label payload length hop limit next header source destination extension headers or payload 17

IPv4 header 0 3 4 11 12 15 16 23 24 31 DSCP/ECN total length version hdr len flags fragment offset identification protocol time to live header checksum source address destination address options or payload Flags will be used for fragmenting packets. 18

Internet control message protocol 0 7 8 15 16 31 type code checksum depends ◮ IPv6 next header : 58 ◮ IPv4 protocol : 1 ◮ similarities between ICMPv6 and ICMPv4 ◮ kind of on L3 purpose, e.g., ◮ destination unreachable ◮ time to live exceeded ◮ neighbour discovery 19

Outline Internet protocol architecture MAC addresses Internet protocol L3 address resolution 20

Neighbour discovery protocol A B PC 0 PC 1 2001:DB8::1 2001:DB8::2 C PC 2 2001:DB8::3 questions: ◮ L2 src, dst ◮ L3 src, dst ◮ ICMPv6 content 21