1. 1 14. Internetworking

2. Prof. Sang-Jo Yoo 2 Contents  Internetworking Terms  Principles of Internetworking  Connectionless Internetworking  The Internet Protocol  Routing Protocols  IPv6(IPNG)

3. Prof. Sang-Jo Yoo 3 MIME BGPFTPHTTPSMTPTELNETSNMP UDP ICMPOSPF IP TCP Internetworking protocols in context within the TCP/IP protocol BGP = border gateway protocol FTP = file transfer protocol HTTP=hypertext transfer protocol ICMP=internet control message protocol IP = internet protocol OSPF= open shortest path first MIME= Multi-purpose internet mail extension SMTP = simple mail transfer protocol SNMP= simple network management protocol TCP = transmission control protocol UDP = user datagram protocol

4. Prof. Sang-Jo Yoo 4 Internetworking terms  Communication Network  A facility that provides a data transfer service among devices attached to the network.  Internet  A collection of communication networks interconnected by bridges and/or routers.  Intranet  Operates within the organization for internal purpose.  End system  A device used to connect one of networks.  Intermediate System  A device used to connect two networks.

5. Prof. Sang-Jo Yoo 5 Internetworking terms  Intermediate System  Layer 1 : Repeaters copy individual bits between cable segments  Layer 2 : Bridges store and forward data link frames between LANs  Layer 3 : Multi-protocol Routers forward packets between dissimilar networks  Layer 4 : Transport Gateways connect byte streams in the transport layer  Above Layer 4 : application Gateways allow internetworking above layer 4

6. Prof. Sang-Jo Yoo 6 Principles of Internetworking  Requirements of internetwork service: provide  a link between networks. At minimum, a physical and link control connection is needed  the routing and delivery of data between processes on different networks  an accounting service  internetworking facility must accommodate a number of differences among networks  different addressing schemes  different maximum packet size  different network-access mechanism  different timeouts  Error recovery/status reporting/ routing tech./user access control  connection, connectionless

7. Prof. Sang-Jo Yoo 7 The TCP/IP Internet: Internet Hierarchy

8. Prof. Sang-Jo Yoo 8  Architectural approaches  two dimensions for describing the internetworking function  the mode of operation(connection-mode or connectionless)  the protocol architecture

9. Prof. Sang-Jo Yoo 9 Internetwork architectures C Sharing protocol of the end systems a) Connection mode Network layer(N) b) Connectionless mode Internet Protocol(I ) c) Bridge data link layer(M)

10. Prof. Sang-Jo Yoo 10 Connection Oriented  Assume that each network is connection oriented  IS connect two or more networks  IS appear as DTE to each network  Logical connection set up between DTEs  Concatenation of logical connections across networks  Individual network virtual circuits joined by IS  May require enhancement of local network services  802, FDDI are datagram services

11. Prof. Sang-Jo Yoo 11 Connection Oriented IS Functions  Relaying  Routing  e.g. X.75 used to interconnect X.25 packet switched networks  Connection oriented not often used  (IP dominant)

12. Prof. Sang-Jo Yoo 12 Connectionless Operation  Corresponds to datagram mechanism in packet switched network  Each NPDU treated separately  Network layer protocol common to all DTEs and routers  Known generically as the internet protocol  Internet Protocol  One such internet protocol developed for ARPANET  RFC 791  Lower layer protocol needed to access particular network

13. Prof. Sang-Jo Yoo 13 Connectionless Internetworking  Advantages  Flexibility  Robust  No unnecessary overhead  Unreliable  Not guaranteed delivery  Not guaranteed order of delivery  Packets can take different routes  Reliability is responsibility of next layer up (e.g. TCP)

14. Prof. Sang-Jo Yoo 14

15. Prof. Sang-Jo Yoo 15  Combining Services

16. Prof. Sang-Jo Yoo 16 Design Issues of IP-controlled Internet  Routing  Datagram lifetime  Fragmentation and re-assembly  Error control  Flow control

17. Prof. Sang-Jo Yoo 17 Routing  End systems and routers maintain routing tables  Indicate next router to which datagram should be sent  Static  May contain alternative routes  Dynamic  Flexible response to congestion and errors  Source routing  Source specifies route as sequential list of routers to be followed  Security  Priority

18. Prof. Sang-Jo Yoo 18 Datagram Lifetime  Datagrams could loop indefinitely  Consumes resources  Transport protocol may need upper bound on datagram life  Datagram marked with lifetime  Time To Live field in IP  Once lifetime expires, datagram discarded (not forwarded)  Hop count  Decrement time to live on passing through a each router  Time count  Need to know how long since last router

19. Prof. Sang-Jo Yoo 19 Fragmentation and Re-assembly  Different packet sizes  When to re-assemble  At destination  Results in packets getting smaller as data traverses internet  Intermediate re-assembly  Need large buffers at routers  Buffer space will be used up storing partial datagrams.  All fragments must go through same router Inhibits dynamic routing  IP re-assembles at destination only

20. Prof. Sang-Jo Yoo 20 Error Control  Not guaranteed delivery  Router should attempt to inform source if packet discarded  Because of time to live expiring  Congestion  FCS errors  Source may modify transmission strategy  May inform high layer protocol

21. Prof. Sang-Jo Yoo 21 Flow Control  Allows routers and/or stations to limit rate of incoming data  Limited in connectionless systems  Send flow control packets  Requesting reduced flow  e.g. ICMP

22. Prof. Sang-Jo Yoo 22 The Internet Protocol  Internet Protocol (IP)  Isolates the transport and application protocols from the messy details of each network.

23. Prof. Sang-Jo Yoo 23  IP services  the interface with a higher layer(e.g. TCP)  Send primitive - used to request transmission of a data unit  Deliver primitive - used to notify a user of the arrival of a data unit Send ( Source Address Destination Address Protocol Type of service indicators Identifier Don’t-fragment identifier Time to live Data length Option data Data ) Deliver ( Source Address Destination Address Protocol Type of service indicators Data length Option data Data )

24. Prof. Sang-Jo Yoo 24  Type of service indicator requests particular QoS and guides routing decision  precedence - a measure of datagram’s relative importance (8 levels)  reliability (normal or high)  delay  throughput  the options parameter  security  source routing  route recording  stream identification  timestamping

25. Prof. Sang-Jo Yoo 25  IP Protocol IP header IHL : internet header length in 32-bit words, minimum is 5,(20 octets) Flag(3 bits) : More bit, Don’t fragment bit and last 1 bit is reserved Protocol : indicates the next higher level protocol at the destination padding(variable) : used to ensure that the datagram header is a multiple of 32 bits

26. Prof. Sang-Jo Yoo 26  IP address  32 bit (network id + host id) Special IP address 0.0.0.0 this host 255.255.255.255 broadcast on LAN 127.x.x.x Loopback 1.0.0.0 to 127.255.255.255 128.0.0.0 to 191.255.255.255 192.0.0.0 to 223.255.255.255

27. Prof. Sang-Jo Yoo 27  Technically, TCP/IP addresses identify interfaces, not system.  In most cases, hosts have but a single interface.  Routers usually support multiple interfaces

28. Prof. Sang-Jo Yoo 28  Type of addresses  Unicast addresses: refer to a single interface; network takes responsibility for delivering the message to that interface.  Multicast addresses: identify sets of interfaces.  This function lets a system generate a message once and delivered to many different recipients.

29. Prof. Sang-Jo Yoo 29  Anycast addresses: refers to one of a set of interfaces  New feature with IPv6.  Includes many interfaces from different systems  The network considers its work complete when it delivers the message to any of the appropriate interfaces.

30. Prof. Sang-Jo Yoo 30 Subnets and Subnet Masks  Allow arbitrary complexity of internetworked LANs within organization  Insulate overall internet from growth of network numbers and routing complexity  Each LAN assigned subnet number  Host portion of address partitioned into subnet number and host number  Local routers route within subnetted network  Subnet mask indicates which bits are subnet number and which are host number

31. Prof. Sang-Jo Yoo 31 Subnet mask of R1 and R2 11111111.11111111.11111111.11100000 255.255.255.224 Terminal B IP x.x.x.00111001 (192.228.17.57) After masking Subnet : 1 Host 25

32. Prof. Sang-Jo Yoo 32  The Internet Control Message Protocol(ICMP)  ICMP provides feedback about problems in communication environment.  ICMP is a user of IP ( not reliable)  ICMP message  Destination unreachable  Time exceeded  Parameter problem - syntactic or semantic error in an IP  Source quench - flow control (rate control)  Redirect - redirect routing  Echo/echo-reply - testing that communication is possible  Timestamp /Timestamp reply - sampling the delay characteristics of the internet  Address mark / Address mark reply

33. Prof. Sang-Jo Yoo 33 ICMP message format

34. Prof. Sang-Jo Yoo 34 IPv6(IPNG)  History  IPv4 : the present IP  32-bit address system cannot accommodate the rapidly increasing IP address demands  IPv5 : experimental real-time Stream Protocol, a connection- oriented internet level protocol  IPv6 : IPNG (IETF: internet engineering task force)  Call for Proposal June, 1992 (RFC 1550)  “The Recommendation for the IP Next Generation Protocol”, Jan,1995 (RFC 1883 ~ RFC 1887)

35. Prof. Sang-Jo Yoo 35  IPv6 Enhancements over IPv4  Expanded address space  128-bit address  Improved Option Mechanism  simplify the protocol, to allow routers to process packets faster  Increased Address Flexibility  anycast, multicast  Support for Resource allocation  pay more attention to type of service, particularly for real-time data  Security Capabilities  authentication, privacy

36. Prof. Sang-Jo Yoo 36  IPv6 Structure define special options that require hop-by-hop processing extended routing, similar source routing packet integrity and authentication privacy IPv6 packet with all extension header

37. Prof. Sang-Jo Yoo 37  IPv6 Header