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4: Network Layer4a-1 IPv6. 4: Network Layer4a-2 History of IPv6 r IETF began thinking about the problem of running out of IP addresses in 1991 r Requires.

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Presentation on theme: "4: Network Layer4a-1 IPv6. 4: Network Layer4a-2 History of IPv6 r IETF began thinking about the problem of running out of IP addresses in 1991 r Requires."— Presentation transcript:

1 4: Network Layer4a-1 IPv6

2 4: Network Layer4a-2 History of IPv6 r IETF began thinking about the problem of running out of IP addresses in 1991 r Requires changing IP packet format - HUGE deal! r While we’re at it, lets change X too r “NGTrans” (IPv6 Transition) Working Group of IETF - June 1996

3 4: Network Layer4a-3 IPv6 Wish List r From “The Case for IPv6” r Scalable Addressing and Routing r Support for Real Time Services r Support of Autoconfiguration (get your own IP address and domain name to minimize administration) r Security Support r Enhanced support for routing to mobile hosts

4 4: Network Layer4a-4 IPv4 Datagram VersionHLen TOSLength IdentFlagsOffset TTLProtocolChecksum SourceAddr DestinationAddr Options (variable) Pad (variable) 048161931 Data

5 4: Network Layer4a-5 IPv6 Datagram VersionTrafficClassFlowLabel PayloadLenNextHeaderHopLimit SourceAddress DestinationAddress 0412162431 Next header/data

6 4: Network Layer4a-6 IPv6 Base Header Format r VERS = IPv6 r TRAFFICE CLASS: specifies the routing priority or QoS requests r FLOW LABEL: to be used by applications requesting performance guarantees r PAYLOAD LENGTH: like IPv4’s datagram length, but doesn’t include the header length like IPv4 r NEXT HEADER: indicates the type of the next object in the datagram either type of extension header or type of data r HOP LIMIT: like IPv4’s Time To Live field but named correctly r NO CHECKSUM (processing efficiency)

7 4: Network Layer4a-7 Address Space r 32 bits versus 128 bits - implications? m 4 billion versus 3.4 X10 38 m 1500 addresses per square foot of the earth surface

8 4: Network Layer4a-8 Addresses r Still divide address into prefix that designates network and suffix that designates host r But no set classes, boundary between suffix and prefix can fall anywhere (CIDR only) r Prefix length associated with each address

9 4: Network Layer4a-9 Addresses Types r Unicast: delivered to a single computer r Multicast: delivered to each of a set of computers (can be anywhere) m Conferencing, subscribing to a broadcast r Anycast: delivered to one of a set of computers that share a common prefix m Deliver to one of a set of machines providing a common servicer

10 4: Network Layer4a-10 Address Notation r Dotted sixteen? m 56 r Colon hexadecimal notation (8 groups) m 69DC:8768:9A56:FFFF:0:5634:343 r Or even better with zero compression (replace run of all 0s with double ::) r Makes host names look even more attractive huh?

11 4: Network Layer4a-11 Special addresses r Ipv4 addresses all reserved for compatibility m 96 zeros + IPv4 address = valid IPv6 address r Local Use Addresses m Special prefix which means “this needn’t be globally unique” m Allow just to be used locally m Aids in autoconfiguration

12 4: Network Layer4a-12 Datagram Format r Base Header + 0 to N Extension Headers + Data Area

13 4: Network Layer4a-13 Extensible Headers r Why? r Saves Space and Processing Time m Only have to allocate space for and spend time processing headers implementing features you need r Extensibility m When add new feature just add an extension header type - no change to existing headers m For experimental features, only sender and receiver need to understand new header

14 4: Network Layer4a-14 Flow Label r Virtual circuit like behavior over a datagram network r A sender can request the underlying network to establish a path with certain requirements Traffic class specifies the general requirements (ex. Delay < 100 msec.) r If the path can be established, the network returns an identifier that the sender places along with the traffic class in the flow label r Routers use this identifier to route the datagram along the prearranged path

15 4: Network Layer4a-15 ICMPv6 r New version of ICMP r Additional message types, like “Packet Too Big” r Multicast group management functions

16 4: Network Layer4a-16 Summary like IPv6 m Connectionless (each datagram contains destination address and is routed separately) m Best Effort (possibility for virtual circuit behavior) m Maximum hops field so can avoid datagrams circulating indefinitely

17 4: Network Layer4a-17 Summary New Features r Bigger Address Space (128 bits/address) m CIDR only m Any cast addresses r New Header Format to help speed processing and forwarding m Checksum: removed entirely to reduce processing time at each hop m No fragmentation r Simple Base Header + Extension Headers m Options: allowed, but outside of header, indicated by “Next Header” field r Ability to influence the path a datagram will take through the network (Quality of service)

18 4: Network Layer4a-18 Transition From IPv4 To IPv6 r Not all routers can be upgraded simultaneous m no “flag days” m How will the network operate with mixed IPv4 and IPv6 routers? r Two proposed approaches: m Dual Stack: some routers with dual stack (v6, v4) can “translate” between formats m Tunneling: IPv6 carried as payload n IPv4 datagram among IPv4 routers

19 4: Network Layer4a-19 Dual Stack Approach

20 4: Network Layer4a-20 Tunneling IPv6 inside IPv4 where needed

21 4: Network Layer4a-21 6Bone r The 6Bone: an IPv6 testbed r Started as a virtual network using IPv6 over IPv4 tunneling/encapsulation r Slowly migrated to native links for IPv6 transport r RFC 2471

22 4: Network Layer4a-22 Recent History r First blocks of IPv6 addresses delegated to regional registries - July 1999 r 10 websites in domain that can be reached via an IPv6 enhanced client via an IPv6 TCP connection ( - it was 5 a year ago (not a good sign?)

23 4: Network Layer4a-23 IPv5? r New version of IP temporarily named “IP - The Next Generation” or IPng r Many competing proposals; name IPng became ambiguous r Once specific protocol designed needed a name to distinguish it from other proposals r IPv5 has been assigned to an experimental protocol ST

24 4: Network Layer4a-24 Network Address Translation (NAT)

25 4: Network Layer4a-25 Background r IP defines private intranet address ranges m - (Class A) m - (Class B) m - (Class C) r Addresses reused by many organizations r Addresses cannot be used for communication on Internet

26 4: Network Layer4a-26 Problem Discussion r Hosts on private IP networks need to access public Internet r All traffic travels through a gateway to/from public Internet r Traffic needs to use IP address of gateway r Conserves IPv4 address space m Private IP addresses mapped into fewer public IP addresses m Will this beat Ipv6?

27 4: Network Layer4a-27 Scenario Gateway Host A BMRC Server All Private Network hosts must use the gateway IP address Private Network Public Internet Public network IP address, globally unique Same private network IP addresses may be used by many organizations

28 4: Network Layer4a-28 Network Address Translation Solution r Special function on gateway m IP source and destination addresses are translated m Internal hosts need no changes r No changes required to applications r TCP based protocols work well r Non-TCP based protocols more difficult r Provides some security m Hosts behind gateway difficult to reach m Possibly vulnerable to IP level attacks

29 4: Network Layer4a-29 NAT Example NAT Gateway Server Address Translator TCP Connection 1

30 4: Network Layer4a-30 TCP Protocol Diagram ClientServer SYN, ACK Packet 0:50 ACK 0:50 FIN FIN, ACK Source IP Address Destination IP Address Checksum Sequence Number Dest Port NumberSource Port Number TCP Header..... IP Header..... ACK SYN SYN flag indicates a new TCP connection

31 4: Network Layer4a-31 TCP NAT Example Server Internet NAT Gateway PROTO SADDR DADDR SPORT DPORT FLAGS CKSUM TCP 40960 80 SYN 0x2436 2 2. NAT gateway sees SYN flag set, adds new entry to its translation table. It then rewrites the packet using gateway’s external IP address, Updates the packet checksum. PROTO SADDR DADDR SPORT DPORT FLAGS CKSUM TCP 80 40960 SYN, ACK 0x8041 3 3. Server responds to SYN packet with a SYN,ACK packet. The packet is sent to the NAT gateway’s IP address. Client Server IPAddr Port IPAddr Port NATPort 1049 80 40960............ NAT Translation Table PROTO SADDR DADDR SPORT DPORT FLAGS CKSUM TCP 1049 80 SYN 0x1636 1 1. Host tries to connect to web server at It sends out a SYN packet using its internal IP address, PROTO SADDR DADDR SPORT DPORT FLAGS CKSUM TCP 80 1049 SYN, ACK 0x7841 4 4. NAT gateway looks in its translation table, finds a match for the source and destination addresses and ports, and rewrites the packet using the internal IP address.

32 4: Network Layer4a-32 Load Balancing Servers with NAT r Single IP address for web server r Redirects workload to multiple internal servers Server NAT Gateway (Virtual Server) Private Intranet Public Internet

33 4: Network Layer4a-33 Load Balancing Networks with NAT NAT Gateway r Connections from Private Intranet split across Service Providers 1 and 2 r Load balances at connection level m Load balancing at IP level can cause low TCP throughput Private Intranet Service Provider 1 Service Provider 2 Network X

34 4: Network Layer4a-34 NAT Discussion r NAT works best with TCP connections r NAT breaks End-to-End Principle by modifying packets r Problems m Connectionless UDP (Real Audio) m ICMP (Ping) m Multicast m Applications use IP addresses within data stream (FTP) r Need to watch/modify data packets

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