l11 IPv6,Anycast,Multicast

l11 IPv6,Anycast,Multicast - Anycast Communicate with any...

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Unformatted text preview: Anycast Communicate with any one of a set of nodes Can do this with DNS $ dig www.google.com ... ;; ANSWER SECTION: www.google.com. 604799 IN CNAME www.l.google.com. www.l.google.com. 300 IN A 74.125.19.103 www.l.google.com. 300 IN A 74.125.19.104 www.l.google.com. 300 IN A 74.125.19.147 www.l.google.com. 300 IN A 74.125.19.99 Anycast at IP layer DNS allows anycast through name address mappings Sometimes we need it at layer 3 itself- Single IP address refers to multiple hosts- Need to talk to any one of them Example: DNS root servers- Would like to scale number of root servers with Internet- Cant use DNS (remember root servers hard-coded)- Want to query closest root server Anycast in Forwarding Tablse Remember, forwarding is longest-prefix-match An anycast address is a /32 address A single router may have multiple entries for the address Anycast best used in services where separate packets might go to different destinations The Cost A /32 routing entry! Multiple /32 routing entries! Further Advantages Geographic scoping Distributed Denial of Service (DDoS)- Load from DDoS is distributed across many anycast nodes F root server (192.5.5.241) now in 46 locations! Try the following: dig +norec @f.root-servers.net hostname.bind chaos txt I think we have a problem- Projected use of /8 blocks- From A Pragmatic Report on IPv4 Address Space Consumption , Tony Main, Cisco Sys- tems. IPv6 Work started in 1994 Basic protocol published in 1998 [RFC 2460] Brief lull, the progress in 2003-6 Hard push within IETF today for adoption IPv6 Key Features 128 bit addresses- Autoconfiguration Simplifies basic packet format through extension headers- 40 byte base header- Make uncommonly used fields optional IPv6 Addresses [RFC 4291] | n bits | 128-n bits | +-------------------------------+---------------------------------+ | subnet prefix | interface ID | +-------------------------------+---------------------------------+ Written as 8, :-separated 16-bit hex numbers- Example: 2001:470:806d:1:0:0:0:9- Can omit a single run of 0s with :: - Use brackets in URLs: http://[2001:470:806d:1::9]:80/- Can write low 32-bits like IPv4: 64:ff9b::171.66.3.9 Like IPv4, specify subnet prefix with /- E.g., 2001:db8:122:344::/64 Most IPv6 networks use 64-bit subnet prefix, and end users should receive multiple /64s [RFC 6177] IPv6 address allocation Normal global unicast addresses start 2000::/3- IANA doles out unicast prefixes to RIRs A few other special prefixes are assigned- :: (all 0s) is unspecified address, ::1 is localhost- Rest of 0::/8 used for IPv4 compatibility- fc00::/7 used for local addresses [RFC 4193] (kind of like IPv4 addresses 10/8, 172.16/20, 192.168/16 [RFC 1918] )- fe80::/10 used for link-local addresses- ff00::/8 used for multicast Over 85% of address space reserved- In the unlikely event we exhaust 2000::/8 , can be more parsimonious with some other slice IPv6 multicast addresses...
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This note was uploaded on 04/02/2012 for the course CS 144 at Stanford.

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l11 IPv6,Anycast,Multicast - Anycast Communicate with any...

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