TDC 375 Winter 2002 John Kristoff DePaul University jtk depaul edu 1 312 362 5878 DePaul University Chicago IL 60604 John Kristoff The Internet Protocol IP 1 TDC 375 Winter 2002 John Kristoff DePaul University 2 Will layer 2 networking suffice TDC 375 Winter 2002 John Kristoff DePaul University Packet independence A hardware independent interface Packet fragmentation capability A common communications format Scalable routing Globally unique addresses Internetworking for data link technologies Layer 3 usually provides 3 An IP Router or gateway TDC 375 Winter 2002 John Kristoff DePaul University Layer 3 switch router layer 3 switch Official pronounciation is really rooter They can forward based on various metrics They make automatic forwarding decisions Dynamic routing algorithms often used 4 Directs packets toward ultimate destination Connects heterogenous networks Usually a special purpose dedicated device IP Routing TDC 375 Winter 2002 John Kristoff DePaul University Destination address driven Manually configured routes Static routing 5 Protocol for route exchange and computation Dynamic routing Autonomous system interior exterior Scope TDC 375 Winter 2002 John Kristoff DePaul University The Internet Glue Fairly simple Unreliable Connectionless Standardized in RFC 791 Internet protocol IP 6 IP addresses TDC 375 Winter 2002 John Kristoff DePaul University e g 140 192 1 6 7 Usually written as dotted decimal notation Local administrators assign the suffix host Global authories assign a prefix network Unique address for each IP interface 32 bit fixed size Virtual not bound to hardware IP address types TDC 375 Winter 2002 John Kristoff DePaul University Preferably one to nearest defined for IPv6 Anycast one to one of many 8 Special case of a multicast usually best avoided Broadcast one to all Receivers join listen to multicast group address Multicast one to many Source address should always be unicast Unicast one to one TDC 375 Winter 2002 John Kristoff DePaul University IP address notation 9 TDC 375 Winter 2002 John Kristoff DePaul University Special IP addresses 10 TDC 375 Winter 2002 John Kristoff DePaul University Classful IP addressing 11 TDC 375 Winter 2002 John Kristoff DePaul University Classful address sizes 12 TDC 375 Winter 2002 John Kristoff DePaul University Example IP network 13 TDC 375 Winter 2002 John Kristoff DePaul University 14 Example IP router addressing TDC 375 Winter 2002 John Kristoff DePaul University Class B too big class C too small 15 Lack of support for different sized networks Misappropriation of addresses Address depletion Route table size Internet growth Limitations of classful addressing TDC 375 Winter 2002 John Kristoff DePaul University Variable length subnet masks VLSM Classless interdomain routing CIDR Supernetting Subnetting IP addressing solutions 16 TDC 375 Winter 2002 John Kristoff DePaul University Subnetting 17 Subnet mask TDC 375 Winter 2002 John Kristoff DePaul University 11111111 11111111 11111111 10000000 A 25 or 255 255 255 128 subnet mask is 18 You may want to convert to binary for clarity or 140 192 1 6 25 140 192 1 6 s subnet mask is 255 255 255 128 Dotted decimal or notation Prefix network is no longer classful The bit length of the prefix network TDC 375 Winter 2002 John Kristoff DePaul University 19 total number of hosts that can be addressed directed broadcast address in dotted decimal subnet mask in dotted decimal notation Given 140 192 50 8 20 what is the Example Using subnet masks Supernetting TDC 375 Winter 2002 John Kristoff DePaul University Equals 199 63 0 0 20 Combine 199 63 0 0 24 to 199 63 15 0 24 Maybe do this If class B too big class C too small 20 Combine smaller blocks into larger aggregate Example Using Supernets TDC 375 Winter 2002 John Kristoff DePaul University 21 Can you think of any reason why the customer might have less than that maximum How many if any maximum free IP addresses will the customer have at their disposal What is the address space assigned in the example above in slash notation If a customer needs to address 300 hosts how might the ISP assign them address space Given that ISP has 128 15 0 0 16 CIDR TDC 375 Winter 2002 John Kristoff DePaul University 22 http www employees org tbates cidr report html Internet CIDR report 199 5 6 0 22 one time Advertise 199 5 6 0 24 199 5 6 1 24 199 5 6 2 24 and 199 5 6 1 24 separately So instead of advertising Routes advertised as smaller CIDR blocks Use supernetting for routing tables Example Using CIDR TDC 375 Winter 2002 John Kristoff DePaul University 23 If these routes are received from another provider can you think of any reason why they might not be able to be CIDR ized What is the smallest number of CIDR announcements that this ISP can make Given that an ISP announces netblocks 64 5 0 0 20 64 5 16 0 20 192 0 2 0 25 and 192 0 2 192 26 and 192 0 2 128 26 VLSM TDC 375 Winter 2002 John Kristoff DePaul University 24 But internally may use 140 192 0 0 17 140 192 128 0 24 140 192 129 0 24 and so on An organization may have 140 192 0 0 16 External view of AS does not change Can be used to build internal hierarchy Allows efficient use of address space Multiple subnet sizes in a single AS Example Using VLSM TDC 375 Winter 2002 John Kristoff DePaul University 25 Overall growth for organization is 500 hosts year Satellites vary from 200 to 700 total addresses Main site uses approximately 50 of addresses About 7000 hosts exist on entire network today 6 satellite sites and 1 main office center Given an address space of 140 192 0 0 16 to work with assign netblocks and addresses based on the following network Obtaining IP addresses TDC 375 Winter 2002 John Kristoff DePaul University 10 0 0 0 8 172 16 0 0 12 192 168 0 0 16 Must not appear on the public Internet NOT globally unique 26 RFC 1918 defines private address netblocks ISPs assign addresses to end end users Regional registries delegate ARIN RIPE APNIC IANA has global authority for assignment TDC 375 Winter 2002 John Kristoff DePaul University IP datagram layout 27 Inside an IPv4 datagram TDC 375 Winter 2002 John Kristoff DePaul University 28 Rarely used but if so usually within single AS An indication of quality class of service Type of Service now DiffServ field Will usually be equal 5 in decimal Length of the IP header in 32 bit words Header length Binary 0100 equals what in decimal Version field TDC 375 Winter 2002 John Kristoff DePaul University Bit 0 reserved others control fragmentation Flags Experimental