Lecture 14 IP Wrap up Dejian Ye Software School Fudan University
1 Lecture 14 IP Wrap up Dejian Ye Software School Fudan University
Outline The recurring IP address space problem IPv6 NAT Tunneling /Overlays Network Management 》 Autoconfiguration ))SNMP(notes only 2
2 Outline The recurring IP address space problem IPv6. NAT. Tunneling / Overlays Network Management »Autoconfiguration »SNMP (notes only)
IP Address space Address space crunch 1: Classful routing 》128“ class a” blocks of2^24 addresses( too big) >)16k"class B"blocks of 216 addresses(still too big) 》2M“ class c” blocks( often too smal) >)Result: Exceptionally wasteful allocation MIT still has 180.0.08 -- 16M addresses for 30k people >) Solution CIDR(cider" ). Classful Inter-Domain Routing Removed classness Now can route on arbitrary power of two boundary “ slash” notation:/8=255.0.0.0,/16=255255.0.0, etc 3
3 IP Address space Address space crunch 1: Classful routing » 128 “class A” blocks of 2^24 addresses (too big) » 16k “class B” blocks of 2^16 addresses (still too big) » 2M “class C” blocks (often too small) » Result: Exceptionally wasteful allocation – MIT still has 18.0.0.0/8 -- 16M addresses for 30k people » Solution: CIDR (“cider”). Classful Inter-Domain Routing. – Removed classness. – Now can route on arbitrary power of two boundary – “slash” notation: /8 = 255.0.0.0, /16 = 255.255.0.0, etc
IP address space 2 How many IP addresses? 4B How many 》 People?6.5B Cell phones? 2.2B(roughly) > Embedded computers?(???, but huge) What happens if you network all of the devices in your house? > Big reality in 2005: We' re about 50% used CIDR Tighter allocation policies; voluntary IP reclamation NAT (talk about soon) Will it happen? Maybe, maybe not. ButI wouldn't bet against it But even if not, put on architecture hat and think about the problems 4
4 IP address space 2 How many IP addresses? 4B How many… » People? 6.5B » Cell phones? 2.2B (roughly) » Embedded computers? (???, but huge) » What happens if you network all of the devices in your house? » Big reality in 2005: We’re about 50% used. – CIDR – Tighter allocation policies; voluntary IP reclamation – NAT (talk about soon) Will it happen? Maybe, maybe not. But I wouldn’t bet against it. But even if not, put on architecture hat and think about the problems…
Efficiency vs Convenience Exact allocation vs Routing Table size >)If I have 20 computers, how do you alloc? 127=32 30 usable): Waste 12 /28=16(14)+/29(8,6 usable): Waste4 Can't get any better. Weve traded a bit of address efficiency for two BGP routing table entries Exact allocation ys, Future Growth > Suppose you buy more computers Could add a new netblock(more table entries) Could move to a bigger one(re-addressing) Update computers Update routers Update DNS Update address allocation registries Maybe have to fix some hard-coded addresses, if you were bad > Partial solution: DHCP (we'll talk about later today) 5
5 Efficiency vs. Convenience Exact allocation vs. Routing Table Size » If I have 20 computers, how do you alloc? – /27 = 32 (30 usable): Waste 12 – /28 = 16 (14) + /29 (8, 6 usable): Waste 4 – Can’t get any better… – We’ve traded a bit of address efficiency for two BGP routing table entries. Exact allocation vs. Future Growth » Suppose you buy more computers – Could add a new netblock (more table entries) – Could move to a bigger one (re-addressing) Update computers Update routers Update DNS Update address allocation registries Maybe have to fix some hard-coded addresses, if you were bad » Partial solution: DHCP (we’ll talk about later today)