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Computer Networks

Computer Networks. Chapter 9 – Network Layer Addresses. Network Address Examples. LAN A. IP – per interface IPX – per interface IPv6 – per interface CLNP – per node AppleTalk – per interface DECnet – per node. Interface 0. Host X. Interface 1. LAN B.

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Computer Networks

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  1. Computer Networks Chapter 9 – Network Layer Addresses CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  2. Network Address Examples LAN A • IP – per interface • IPX – per interface • IPv6 – per interface • CLNP – per node • AppleTalk – per interface • DECnet – per node Interface 0 Host X Interface 1 LAN B CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  3. Hierarchical Addresses, Fixed Bdry • N nodes in network, N large • N too big to keep routing info with N rows • Aggregate addresses so all nodes in one area have same prefix…. Hierarchical • Balance size K of subnetwork with number of subnetworks L • Introduce more levels if K and L too big CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  4. Hierarchical Addresses, Fixed Bdry 37.*.* • Level i+1 routers route amongst Level i networks; • Level 1 routers route to end nodes in same subnetwork 22.*.* 41.*.* Level 2 subnetworks CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  5. Hierarchical Addresses, Fixed Bdry 37.23.* 22.56.* 37.3.* 37.1.* 22.23.* 22.3.* 37.12.* 41.12.* 22.12.* 41.97.* 41.17.* 3-level address: 22.1.* 41.5.* Level 2 subnetwork Level 1 subnetwork end host Level 3 subnetworks CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  6. Hierarchical Addrs, Flexible Bdry 722* • Really, no need for router to know its level • No need to have fixed fields for address levels • Subnet address is just a prefix 71* 723* 7* backbone 5* 31* 5221* 522* 55* 315* 311* 551* CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  7. Owning vs. Renting • Initially, IP addresses obtained in blocks from IANA • Blocks given according to size and order of request • Results in non-topological addresses • Now addresses given to providers • Providers distribute sub-addresses • Address must change with provider… CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  8. Address Types • Unicast – single node destination • Multicast – group of nodes destination • Broadcast – all nodes are destinations • May restrict to subnetwork • May restrict number of hops • Anycast – to any one of a group of nodes • Useful for service discovery CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  9. IPv4 Addresses • RFC 791 – generically, IP • 4 octets long (32 bits) • Link and host parts (boundary varies with subnetwork) • Subnet mask used to define boundary • 1’s where subnet bits are, 0’s for host bits • In practice, contiguous bits • Address depends on subnetwork! CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  10. Obtaining IP Addresses • Manually configured address and mask • Obtain from server • BOOTP (RFC 951) • DHCP (RFC 1531) • RARP (RFC 903) • Start with LAN address, and either broadcast to or know address of server (BOOTP, DHCP) • Server provides mask and address CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  11. IPv4 Addresses (original) Dotted Decimal 0 net host 1.0.0.0 to 127.255.255.255 Class A address 1 0 net host 128.0.0.0 to 191.255.255.255 Class B address 1 1 0 net host 192.0.0.0 to 223.225.225.225 Class C address 224.0.0.0 to 239.225.225.225 1 1 1 0 Multicast address Class D address 1 1 1 1 0 reserved 240.0.0.0 to 247.255.255.255 Class E address CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  12. Special IPv4 Addresses Dotted Decimal 00000000000000000000000000000000 0.0.0.0 This host 000000…0000000 host 0.x.y.z Host on this network 11111111111111111111111111111111 225.225.225.225 Broadcast on local network net 111111…11111 Broadcast on remote network 127.a.b.c 127 anything loopback CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  13. Subnet Mask 1 0 network subnetwork host • Flexible subnet mask not supported by old routing protocols (RIP, EGP, early BGPs) • Solves “Three Bears Problem” • CIDR Network address 11111111111111111111111111 000000 Subnet mask CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  14. CIDR • Classless InterDomain Routing (RFC 1519) • Specify subnet by dotted decimal (filling in host part with 0’s)/<bits in network address> • Example: 227.128.64.64/27 has 32-27=5 bits of host address • Allows geographic distribution of Class C’s: • 194.0.0.0 – 195.255.255.255 to Europe • 198.0.0.0 – 199.255.255.255 to Africa • 200.0.0.0 – 201.255.255.255 to Cent. & So. Amer. • 202.0.0.0 – 203.255.255.255 to Asia & Pacific CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  15. IPX Addresses • 10 bytes long • Top 4 are network part • Bottom 6 are node part • Autoconfiguration – • node part = MAC addr on IEEE 802 LANs • Also easy to get MAC addr from IPX addr CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  16. IPX+ Addresses • 16 bytes long • New top 6 are domain number • Obtained automatically from service provider • Bottom 10 as before • One mode of IPv6 resembles this • Extra header added after IPX header • Old routers only look at old header • In domain, route on 4 byte net part • Boundary routers route on 6 byte domain CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  17. IPv6 Addresses • 16 byte addresses (128 bits) • A.k.a. IPng (next generation) • Needed as 32-bit address space “ran out” • Has separate Ethertype (naughty bridges) • Addresses (see RFC 2373) written as • Colon separated hex – 0:0:0:0:0:0:E87F:4001 • Shortcut 0’s - ::E87F:4001 • Allow dotted decimal IP addresses in last 32 bits ::228.127.64.1 • Prefix written as address/prefix length (CIDR) CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  18. EUI-64 • IEEE defined 8-byte address space for “next-generation” LANs • EUI-48 is standard 48-bit address • How to expand? • Longer OUI, same address block? • Same OUI, longer address block? • Consider implications… CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  19. IPv6 Address Conventions • ::0 (this network and node) • ::1 (loopback) • ::IPv4 (bottom 32 bits IPv4 address, rest 0) • ::FFFF:IPv4 (bottom 32 bits are IPv4, next are FFFF, rest 0 – for IPv4 only nodes) • 2000::/3 (normal aggregatable unicast – bottom 8 bytes is EUI-64* node address) • FE80::/10 (link-local – bottom 8 bytes EUI-64*, not to be forwarded) • FEA0:/10 (site-local – bottom 8 node, next 2 subnet ID, not sent off-site) • Anycast – link prefix, then all 0’s • FF00::/8 (Multicast – flags/8, scope/4, then 112 bits of address) CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  20. IPv4 to IPv6 Transition • IPv6 specification delayed • IPv4 improvements made meanwhile: • CIDR addressing, variable subnet masks • DHCP for address configuration & reuse • NAT address sharing & reuse • Dual stack nodes • Translators (NAT, e.g.) CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  21. CLNP Addresses • Connectionless Network Layer Protocol • ISO defined, used by DECnet Phase V, ATM, CDPD (cellular digital packet data) • Variable length addresses, max 20 octets • Extra octet to specify length • Area/ID(0-8)/SEL(1) • Area is larger than single link – like network • ID has no topological significance – like MAC • SEL is like DSAP/SSAP or protocol CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  22. CLNP Addresses IDP • Globally defined part is variable • IDP = initial domain part • AFI = Authority and Format Identifier • IDI = Initial Domain Identifier • DSP = Domain-specific Part • Locally defined part also variable (>=2) AFI IDI DSP ID SEL Locally defined 0-8 octets 1 octet Globally defined CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  23. AppleTalk Addresses • 3 byte addresses • 2 bytes net (can specify range for large LAN) • 1 byte node • Autoconfiguration • See chapter 11! CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  24. DECnet Addresses • Phase III – 2-byte addresses, no hierarchy • Phase IV – 2-byte addresses • 6 bit area • 10 bit node • Used CLNP for packet format – delayed… • Map DECnet address to Ethernet • Force top 4 bytes to be AA-00-04-00 • Reassign NIC address when DECnet boots • Better boot first! CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

  25. Network Address Translation (NAT) • NAT box has set of globally unique network addresses it can assign • Local nodes have only locally significant addresses • NAT assigns global address to local node • Extend by assigning (address,port) pairs to (address,port) pairs • Issues with addresses passed (FTP), etc. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman

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