iL iLab ab Lab 1+2 The Basics / Static Routing Consultation - PowerPoint PPT Presentation

Lehrstuhl für Netzarchitekturen und Netzdienste Institut für Informatik Technische Universität München iL iLab ab Lab 1+2 The Basics / Static Routing

Consultation hours  We will introduce consultation hours  Starting next week  Short (~15 min)  Questions regarding important problems  Blocking you for a long time  Comprehending  At the followin owing times: s:  Tuesday 1300  Wednesday 1400  Thursday 1300  Friday 1300 iLab: The Basics / Static Routing 2

Textbook  Comput puter er Networ tworks: ks: A Sy Syst stem em ‘ s s Approa proach  Larry L. Peterson, Bruce S. Davie  German Translation: „Computernetze“  Dpunkt.Verlag  ISBN: 389864491X  Comprehensive Textbook for the iLab (and the GRNVS lecture, too) Picture: Amazon.com iLab: The Basics / Static Routing 3

Background and History of the Internet  Wher here Wizards ards Stay ay Up Late te: The e Origins igins Of T The e Interne ernet  Katie Hafner, Matthew Lyon  German Translation: Arpa Kadabra oder Die Geschichte des Internet  Dpunkt.Verlag  ISBN: 3898645517  The Internet ‘ s history  First networks  First RFC  The way from the ARPA-Net to the Internet Picture: Amazon.com  The way from the research project to a commercial network iLab: The Basics / Static Routing 4

Agenda  Layered Internet Model and Internet Architecture  Layer 2 Addresses  Internet Protocol and IP Addresses (Layer 3)  Address Resolution Protocol (ARP)  Introduction to the Static Routing Exercise (Lab 2) iLab: The Basics / Static Routing 5

Agenda  Layered Internet Model and Internet Architecture  Layer 2 Addresses  Internet Protocol and IP Addresses (Layer 3)  Address Resolution Protocol (ARP)  Introduction to the Static Routing Exercise (Lab 2) iLab: The Basics / Static Routing 6

ISO/OSI Layer Model (1979-1983) Applications, e.g. HTTP , FTP , … Application Layer 7 Representation of data 6 Presentation Layer 5 Management of Sessions Session Layer Transport, e.g. TCP , UDP , SCTP 4 Transport Layer 3 Network Layer Routing, e.g. IP 2 Data Link Layer Transmission of frames Physical layer, e.g. Ethernet 1 Physical Layer iLab: The Basics / Static Routing 7

Internet Layer Model vs. ISO/OSI 7 Applications 4 Application Layer 6 http, ftp, telnet, smtp, pop, … 5 End-to-end data transport 3 Transport Layer 4 tcp, udp, sctp, … 2 Routing in the internet Internet Layer 3 IPv4, IPv6 2 Interface to the physical medium 1 Link Layer Ethernet, WLAN, Token Ring, FDDI, … 1 • Alternative name: TCP/IP protocol hierarchy • Adaptation of the abstract ISO/OSI layer model for the internet • ISO/OSI layers 5, 6, 7 and layers 1, 2 are aggregated x = Equivalent to ISO/OSI iLab: The Basics / Static Routing 8

Horizontal Communication 4 Application Application 3 TCP TCP 2 IP IP IP IP 1 Net 1 Net 1 Net 2 Net 2 Net 3 Net 3 Router Router Telephone, SDH / SONET WLAN Modem (Hi-Speed Fiber) • Horizo rizont ntal l communica unicatio tion n = logical communication between instances of the same protocol layer over an abstract medium • Only the lowest layer has a real (indirect) connection with the partner instance iLab: The Basics / Static Routing 9

Vertical Communication 4 Application Application 3 TCP TCP 2 IP IP IP IP 1 Net 1 Net 1 Net 2 Net 2 Net 3 Net 3 Router Router Telephone, SDH / SONET WLAN Modem (Hi-Speed Fiber) • Vert rtical ical communic municatio tion n = Instances of a protocol layer communicate with instances of protocol layers above or below. iLab: The Basics / Static Routing 10

Cooperation of Protocol Instances: PDUs  A service provides a Service Access Point (SAP) to the layer above it  Protocol Data Units (PDUs) are encapsulated  TCP/UDP adds process addressing (ports) to IP  TCP adds reliability to IP  IP routes data packets through the network to the destination 4 Data Application TCP-Header Data 3 Transport Layer bzw. UDP-Header Data 2 IP-Header TCP/UDP-Header Data Internet Layer 1 Link Layer MAC/LLC-Header IP-Header TCP/UDP-Header Data Trailer iLab: The Basics / Static Routing 11

Internet Architecture: Common Design Decisions  Hold no information (state) in nodes between sender of data and destination (e.g. no need for resynchronisation)  All information specific for the stream is stored only at the sender and the destination of data: End-to to-end end princ nciple ple  Separation of packet forwarding from one hop to the next and the creation of routing tables  Routing vs. Forwarding iLab: The Basics / Static Routing 12

Agenda  Layered Internet Model and Internet Architecture  Layer 2 Addresses  Internet Protocol and IP Addresses (Layer 3)  Address Resolution Protocol (ARP)  Introduction to the Static Routing Exercise (Lab 2) iLab: The Basics / Static Routing 13

Layer 2 Adresses  MAC addresses (also referred to as “ physical address ” )  Specific for the network type, e.g. Ethernet, Bluetooth, ATM  Are not unique for all network types  Ethernet / WLAN 48 Bit long (e.g.: aa:bb:cc:dd:ee:ff ) Contains information about vendor and product   MAC addresses are not hierarchically issued, e.g.:  Device with MAC aa:bb :bb:cc :cc:dd :dd:ee :ee:ff ff may be located in the US  Device with MAC aa: a:bb bb:cc :cc:dd :dd:ee :ee:fe fe may be located in Japan Q: Why don ’ t we use MAC addresses for addressing devices in the Internet?  Routing would not scale as every router would need to know the route to every possible destination. No aggregation! iLab: The Basics / Static Routing 14

Agenda  Layered Internet Model and Internet Architecture  Layer 2 Addresses  Internet Protocol and IP Addresses (Layer 3)  Address Resolution Protocol (ARP)  Introduction to the Static Routing Exercise (Lab 2) iLab: The Basics / Static Routing 15

TCP/IP Protocol Family – Overview  „TCP/IP “ is used often as a synonym for a whole family of protocols  The TCP/IP family and the ISO/OSI layer model: Session Layer Transport Layer TCP UDP IGMP ICMP IP Network Layer ARP RARP Data Link Layer  ICMP and IGMP use IP like an application layer (ISO/OSI) protocol, but are assigned to the network layer (ISO/OSI)  Application layer (ISO/OSI) protocols are e.g. FTP, TELNET or SMTP iLab: The Basics / Static Routing 16

Routing Inside the Internet  IP addresses are 32 bit long  this results in 2^32 possible host addresses  A naive approach would result in huge routing tables, a router would need to know all routes to all end systems  impossible  Bette ter approach: proach: Hier erarch archical cal Addre dress ssing ing  Use first n bit of the IP address for addressing the network  Use last 32 - n bit of the IP address for addressing the host inside the network  Effect:  A router only needs to know how to reach the hosts within the own network  For reaching hosts outside the own network, the router only needs to know the router that „cares “ for the destination network iLab: The Basics / Static Routing 17

Main Properties of IP  Paket-switched best effort service  no quality of service (QoS) guaranteed  Connectionless and unreliable transmission:  “ fire and forget ”  Datagrams may get lost  Datagrams may arrive out of order  Transmission errors might occur  No flow control  Congestion in the network might occur  Used in private and public networks  private home networks  enterprise networks  Public (wide area) networks (e.g. in the internet backbone) iLab: The Basics / Static Routing 18

IPv4 Datagram Layout Congestion Control (Explicit Congestion Notification) Don ‘ t Fragment Reserved More Fragments QoS Class DiffServ Codepoint ECN 0 DF MF Bit 0 3 7 15 31 Version Hdr.Len DiffServ Total Length Identifier Flags Fragment Offset IP-Header Time to Live Protocol Header Checksum Source Address Destination Address Options and Padding Data iLab: The Basics / Static Routing 19

IP Address Classes 0 1 2 4 8 16 24 31 0 Net-ID Node-ID 1. Class A: Nets with up to 16 million nodes (prefix: 1 bit/ net: 7 / host: 24) 1 0 Net-ID Node-ID 2. Class B: Nets with up to 65.536 nodes (2/ 14/ 16) 1 1 0 Net-ID Node-ID 3. Class C: Nets with up to 256 nodes (3/ 21/ 8) 1 1 1 0 Multicast Address 4. Class D: used for group communication (multicast) 1 1 1 1 0 Reserved for future use 5. Class E, unused, reserved for future use iLab: The Basics / Static Routing 20

Subnetworks  Purpose: Split the static Class A, B C networks into parts (subnets)  Use:  Makes large (Class A) networks manageable  Easier network administration  Separation of business units  Implemented with subnetwork masks  e.g. 255.255.255.0 iLab: The Basics / Static Routing 21