1. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman1 Computer Networks Chapter 9 – Network Layer Addresses

2. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman2 Network Address Examples IP – per interface IPX – per interface IPv6 – per interface CLNP – per node AppleTalk – per interface DECnet – per node Host X Interface 0 Interface 1 LAN B LAN A

3. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman3 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

4. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman4 Hierarchical Addresses, Fixed Bdry 37.*.* 22.*.* 41.*.* Level 2 subnetworks Level i+1 routers route amongst Level i networks; Level 1 routers route to end nodes in same subnetwork

5. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman5 Hierarchical Addresses, Fixed Bdry 37.3.* 22.23.* 41.5.* 37.12.* 37.23.* 37.1.* 41.97.* 41.12.* 41.17.* 22.56.* 22.3.* 22.12.* 22.1.* Level 3 subnetworks Level 2 subnetwork end host Level 1 subnetwork 3-level address:

6. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman6 Hierarchical Addrs, Flexible Bdry Really, no need for router to know its level No need to have fixed fields for address levels Subnet address is just a prefix backbone 7* 71* 722* 723* 5* 522* 55* 31* 315* 311* 551* 5221*

7. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman7 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…

8. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman8 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

9. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman9 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!

10. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman10 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

11. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman11 IPv4 Addresses (original) 0net 10 101 host Class A address Class B address Class C address 101Multicast address Class D address 101reserved Class E address 1 11 Dotted Decimal 1.0.0.0 to 127.255.255.255 128.0.0.0 to 191.255.255.255 192.0.0.0 to 223.225.225.225 240.0.0.0 to 247.255.255.255 224.0.0.0 to 239.225.225.225

12. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman12 Special IPv4 Addresses 000000…0000000 00000000000000000000000000000000 host This host Host on this network 11111111111111111111111111111111 Broadcast on local network net111111…11111 Broadcast on remote network 127anything loopback Dotted Decimal 0.0.0.0 0.x.y.z 225.225.225.225 127.a.b.c

13. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman13 Subnet Mask networkhost Network address 11111111111111111111111111000000 Subnet mask 10subnetwork Flexible subnet mask not supported by old routing protocols (RIP, EGP, early BGPs) Solves “Three Bears Problem” CIDR

14. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman14 CIDR Classless InterDomain Routing (RFC 1519) Specify subnet by dotted decimal (filling in host part with 0’s)/ 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

15. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman15 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

16. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman16 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

17. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman17 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)

18. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman18 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…

19. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman19 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)

20. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman20 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.)

21. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman21 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

22. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman22 CLNP Addresses 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) AFIIDIDSPIDSEL Globally defined Locally defined IDP 0-8 octets 1 octet

23. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman23 AppleTalk Addresses 3 byte addresses –2 bytes net (can specify range for large LAN) –1 byte node Autoconfiguration –See chapter 11!

24. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman24 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!

25. CEN 5501C - Computer Networks - Spring 2007 - UF/CISE - Newman25 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.