TCP/IP Tutorial and Technical Overview phần 5 ppt

376 TCP/IP Tutorial and Technical Overview For further information about mobility support in IPv6, refer to RFC 3775. 9.7 IPv6 new opportunities IPv6 opens up new opportunities in infrastructure and services as well as in research opportunities. 9.7.1 New infrastructure As new internet appliances are added into the IP world, the Internet becomes a new infrastructure in multiple dimensions:  IPv6 can serve as the next generation wireless core network infrastructure. As described in 9.6, “IPv6 mobility support” on page 372, various capabilities in security, addressing, tunneling and so on have enabled mobility applications.  Additional sensor devices can be connected into the IPv6 backbone with an individual IP address. Those collective sensor networks will become part of the fabric in IPv6 network infrastructure.  “Smart” networks with sufficient bandwidth and quality of service make the Internet available for phone calls and multimedia applications. We expect that next generation IPv6 network will replace traditional telephone network to become the dominant telecommunication infrastructure.  As virtualization is widely deployed in both computing data centers and network services, the IPv6 functions become mandatory in security, in flow label processing, and so on. Next generation data centers and network services will evolve around the IPv6 platforms.  IPv6 can create a new virtual private network (VPN) infrastructure, with inherently built-in tunneling capabilities. It also decouples security boundaries from the organization perimeter in the security policy. We expect that network virtualization is possible with IPv6 VPN on demand provisions and management.  Inside a computer, the traditional I/O bus architecture might be replaced by a pure IP packet exchanged structure. This scheme might further improve the network computing infrastructure by separating the computing and storage components physically. Chapter 9. IP version 6 377 9.7.2 New services The basic features and new functions in IPv6 provide stimulation to new services creation and deployment. Here are some high-level examples. We encourage you to refer to Part 3, “Advanced concepts and new technologies” on page 721 for more details.  Presence Service (refer to Chapter 19, “Presence over IP” on page 707) can be developed on top of Location Based Service (LBS). For example, in pure LBS, movie theaters can post attractive title advertisements to a patron’s mobile device when entering the movie zone. In PS, users can setup additional preferences and other policy attributes. As a result, the underlying network services can be aware of user preference and privacy requirements. So, rather than pushing the advertisement to all patrons in the movie zone, those advertisements have to be filtered and tailored accordingly to “do-not-disturb” or “category-specific” preferences.  Anonymous Request Service (ARS) can be developed by exploiting the new IPv6 address allocation functions. For example, a location address can use a random but unique link ID to send packets in reporting ethical or policy violations within an enterprise or in government services.  Voice and Video over IP (which we call V 2 oIP in IPv6) will replace traditional phone service and provide video services over IPv6. For details about VoIP, refer to Chapter 20, “Voice over Internet Protocol” on page 723. For details about IPTV, refer to Chapter 21, “Internet Protocol Television” on page 745.  Always On Services (AOS) allows V 2 oIPv6 to be ready for service with ease of use. Communication sessions can be kept alive and active using IPv6 mobility functions as well as the IPv6 QoS capability. The “always on” availability is independent of location, movement, or infrastructure.  On-demand Routing Services (ORS) eliminates routing table updates for unused routes, balancing slow-path and fast-path processing especially in V 2 oIPv6 environment.  IPv6 Management Service (IMS) provides address automatic inventory, service provisioning, and service assurance services.  IPv6 Operation Service (IOS) supplies on demand configuration, logging, diagnosis, and control services.  IPv6 Testing Service (ITS) provides capabilities in functional conformance and performance testing for implementations of IETF IPv6 standards or RFCs. Interoperability testing is also a key ITS service. 378 TCP/IP Tutorial and Technical Overview 9.7.3 New research and development platforms In addition to new opportunities for users and network service vendors, there are IPv6 research opportunities for educational and research and development institutions as well. For example:  Historically, one of the IETF IP next generation (IPng) project was the development of the 6Bone, which is an Internet-wide virtual network, layered on top of the physical IPv4 Internet. The 6Bone consists of many islands supporting IPv6 packets, linked by tunnels across the existing IPv4 backbone. The 6Bone was widely used for testing of IPv6 protocols and products. By June 6th, 2006 the 6Bone was phased out per agreements with the IETF IPv6 community. For more information, see: http://www.6Bone.net  The 6NET project demonstrated that growth of the Internet can be met using new IPv6 technology. 6NET built a native IPv6-based network connecting 16 European countries. The network allows IPv6 service testing and interoperability with enterprise applications. For more information, see: http://www.6net.org  Internet2 built an experimental IPv6 infrastructure. The Internet2 consortium (not a network) established IPv6 working group to perform research and education in the following areas: – Infrastructure engineering, operations, and deployment – Education for campus network engineers – Exploring the motivation for use of IPv6 For more information, see: http://ipv6.internet2.edu  Another regional IPv6 example is the MOONv6 project. Moonv6 is just one of the world's largest native IPv6 networks in existence. For more information, see: http://www.moonv6.org/ New open research problems in IPv6 include:  IPv6 and next generation network architecture design: While IPv6 and associated protocols have solved problems of message specification and control management, the architecture of the next generation IPv6 network itself is still under experiment. Chapter 9. IP version 6 379  Network infrastructure and service management: Peer-to-peer (P2P) network applications are available to flood the Internet. However, there is a lack of network and service management and control capability. While we should maintain the access and openness of the Internet, the business and commercial reality in the IP space require fundamental rethinking about network and service management infrastructure support.  Security: In addition to the native security functions supplied in IPv6 protocols, IPv6 network security architecture needs to define how to extend security across upper layers of IP networks: – An integrated security infrastructure combines application security policies to underlying network security capabilities. – An integrated security infrastructure also combines content protection into a distribution and transport security layer.  Real-time control capability: IPv6 quality of service features provide real-time support of voice and multimedia applications. Additional research topics include signaling and integration with IP multimedia subsystems.  IPv6 network virtualization: Automatic configuration inventory and provisioning capabilities have to be studied in order to allocate networking resources and transport on demand. 9.8 Internet transition: Migrating from IPv4 to IPv6 If the Internet is to realize the benefits of IPv6, a period of transition will be necessary when new IPv6 hosts and routers are deployed alongside existing IPv4 systems. RFC 2893 – Transition Mechanisms for IPv6 Hosts and Routers and RFC2185 – Routing Aspects of IPv6 Transition define a number of mechanisms to be employed to ensure both compatibility between old and new systems and a gradual transition that does not impact the functionality of the Internet. These techniques are sometimes collectively termed Simple Internet Transition (SIT) . The transition employs the following techniques:  Dual-stack IP implementations for hosts and routers that must interoperate between IPv4 and IPv6.  Imbedding of IPv4 addresses in IPv6 addresses. IPv6 hosts will be assigned addresses that are interoperable with IPv4, and IPv4 host addresses will be mapped to IPv6.  IPv6-over-IPv4 tunneling mechanisms for carrying IPv6 packets across IPv4 router networks. 380 TCP/IP Tutorial and Technical Overview  IPv4/IPv6 header translation.This technique is intended for use when implementation of IPv6 is well advanced and only a few IPv4-only systems remain. 9.8.1 Dual IP stack implementation: The IPv6/IPv4 node The simplest way to ensure that a new IPv6 node maintains compatibility with existing IPv4 systems is to provide a dual IP stack implementation. An IPv6/IPv4 node can send and receive either IPv6 packets or IPv4 datagrams, depending on the type of system with which it is communicating. The node will have both a 128-bit IPv6 address and a 32-bit IPv4 address, which do not necessarily need to be related. Figure 9-25 shows a dual stack IPv6/IPv4 system communicating with both IPv6 and IPv4 systems on the same link. Figure 9-25 IPv6/IPv4 dual stack system The IPv6/IPv4 node can use stateless or stateful autoconfiguration to obtain its IPv6 address. It can also use any method to obtain its IPv4 address, such as DHCP, BOOTP, or manual configuration. However, if the node is to perform automatic tunneling, the IPv6 address must be an IPv4-compatible address, with the low order 32-bits of the address serving as the IPv4 address. (See 9.2.2, “IPv6 addressing” on page 339.) Conceptually, the dual stack model envisages a doubling-up of the protocols in the internetwork layer only. However, related changes are obviously needed in all transport-layer protocols in order to operate when using either stack. Application changes are also needed if the application is to exploit IPv6 capabilities, such as the increased address space of IPv6. When an IPv6/IPv4 node wants to communicate with another system, it needs to know the capabilities of that system and which type of packet it should send. The IPv6 Host App. TCP IPv4 Ethernet IPv6/IPv4 Host App. TCP IPv4 Ethernet IPv4 Host App. TCP IPv4 Ethernet IPv6 Ethernet Chapter 9. IP version 6 381 DNS plays a key role here. As described in Table 12-2 on page 438, a new resource record type, AAAA, is defined for mapping host names to IPv6 addresses. The results of a name server lookup determine how a node will attempt to communicate with that system. The records found in the DNS for a node depend on which protocols it is running:  IPv4-only nodes only have A records containing IPv4 addresses in the DNS.  IPv6/IPv4 nodes that can interoperate with IPv4-only nodes have AAAA records containing IPv4-compatible IPv6 addresses and A records containing the equivalent IPv4 addresses.  IPv6-only nodes that cannot interoperate with IPv4-only nodes have only AAAA records containing IPv6 addresses. Because IPv6/IPv4 nodes make decisions about which protocols to use based on the information returned by the DNS, the incorporation of AAAA records in the DNS is a prerequisite to interoperability between IPv6 and IPv4 systems. Note that name servers do not necessarily need to use an IPv6-capable protocol stack, but they must support the additional record type. 9.8.2 Tunneling When IPv6 or IPv6/IPv4 systems are separated from other similar systems with which they want to communicate by older IPv4 networks, IPv6 packets must be tunneled through the IPv4 network. IPv6 packets are tunnelled over IPv4 very simply: The IPv6 packet is encapsulated in an IPv4 datagram, or in other words, a complete IPv4 header is added to the IPv6 packet. The presence of the IPv6 packet within the IPv4 datagram is indicated by a protocol value of 41 in the IPv4 header. There are two kinds of tunneling of IPv6 packets over IPv4 networks: automatic and configured. Automatic tunneling Automatic tunneling relies on IPv4-compatible addresses. The decision of when to tunnel is made by an IPv6/IPv4 host that has a packet to send across an IPv4-routed network area, and it follows the following rules:  If the destination is an IPv4 or an IPv4-mapped address, send the packet using IPv4 because the recipient is not IPv6-capable. Otherwise, if the destination is on the same subnet, send it using IPv6, because the recipient is IPv6-capable. 382 TCP/IP Tutorial and Technical Overview  If the destination is not on the same subnet but there is at least one default router on the subnet that is IPv6-capable, or there is a route configured to an IPv6 router for that destination, send it to that router using IPv6. Otherwise, if the address is an IPv4-compatible address, send the packet using automatic IPv6-over-IPv4 tunneling. Otherwise, the destination is a node with an IPv6-only address that is connected through an IPv4-routed area, which is not also IPv6-routed. Therefore, the destination is unreachable. These rules emphasize the use of an IPv6 router in preference to a tunnel for three reasons:  There is less inefficiency, because there is no encapsulating IPv4 header.  IPv6-only features are available.  The IPv6 routing topology will be used when it is deployed in preference to the pre-existing IPv4 topology. A node does not need to know whether it is attached to an IPv6-routed or an IPv4-routed area; it will always use an IPv6 router if one is configured on its subnet and will use tunneling if one is not (in which case it can infer that it is attached to an IPv4-routed area). Automatic tunneling can be either host-to-host, or it can be router-to-host. A source host will send an IPv6 packet to an IPv6 router if possible, but that router might not be able to do the same, and will have to perform automatic tunneling to the destination host itself. Because of the preference for the use of IPv6 routers rather than tunneling, the tunnel will always be as “short” as possible. However, the tunnel will always extend all of the way to the destination host. Because IPv6 uses the same hop-by-hop routing paradigm, a host cannot determine if the packet will eventually emerge into an IPv6-complete area before it reaches the destination host. In order to use a tunnel that does not extend all of the way to the recipient, configured tunneling must be used. The mechanism used for automatic tunneling is very simple: 1. The encapsulating IPv4 datagram uses the low-order 32 bits of the IPv6 source and destination addresses to create the equivalent IPv4 addresses and sets the protocol number to 41 (IPv6). Note: The IP address must be IPv4-compatible for tunneling to be used. Automatic tunneling cannot be used to reach IPv6-only addresses, because they cannot be addressed using IPv4. Packets from IPv6/IPv4 nodes to IPv4-mapped addresses are not tunnelled to because they refer to IPv4-only nodes. Chapter 9. IP version 6 383 2. The receiving node's network interface layer identifies the incoming packets (or packets if the IPv4 datagram was fragmented) as belonging to IPv4 and passes them upward to the IPv4 part of the dual IPv6/IPv4 internetwork layer. 3. The IPv4 layer then receives the datagram in the normal way, reassembling fragments if necessary, notes the protocol number of 41, removes the IPv4 header, and passes the original IPv6 packet “sideways” to the IPv6 part of the internetwork layer. 4. The IPv6 code then processes the original packet as normal. Because the destination IPv6 address in the packet is the IPv6 address of the node (an IPv4-compatible address matching the IPv4 address used in the encapsulating IPv4 datagram), the packet is at its final destination. IPv6 then processes any extension headers as normal and then passes the packet's remaining payload to the next protocol listed in the last IPv6 header. Figure 9-26 on page 384 shows two IPv6/IPv4 nodes separated by an IPv4 network. Both workstations have IPv4-compatible IPv6 addresses. Workstation A sends a packet to workstation B, as follows: 1. Workstation A has received router solicitation messages from an IPv6-capable router (X) on its local link. It forwards the packet to this router. 2. Router X adds an IPv4 header to the packet, using the IPv4 source and destination addresses derived from the IPv4-compatible addresses. The packet is then forwarded across the IPv4 network, all the way to workstation B. This is router-to-host automatic tunneling. 3. The IPv4 datagram is received by the IPv4 stack of workstation B. Because the Protocol field shows that the next header is 41 (IPv6), the IPv4 header is stripped from the datagram and the remaining IPv6 packet is then handled by the IPv6 stack. 384 TCP/IP Tutorial and Technical Overview Figure 9-26 Router-to-host automatic tunneling Figure 9-27 on page 385 shows the host-to-host tunneling scenario. Here workstation B responds as follows: 1. Workstation B has no IPv6-capable router on its local link. It therefore adds an IPv4 header to its own IPv6 frame and forwards the resulting IPv4 datagram directly to the IPv4 address of workstation A through the IPv4 network. This is host-to-host automatic tunneling. 2. The IPv4 datagram is received by the IPv4 stack of workstation A. Because the Protocol field shows that the next header is 41 (IPv6), the IPv4 header is stripped from the datagram and the remaining IPv6 packet is then handled by the IPv6 stack. X Y Ethernet IPv6/IPv4 Router (2) IPv4 Ne t wo r k IPv6/IPv4 Router IPv6/IPv4 Host (1) A IPv6/IPv4 Host (3) B flow label64 nextpayload length hops src: Workstation A (I Pv4-compati bl e) dst: Workstation B (I Pv4-compati bl e) payl oad nxt:41 src: Workstation A (IPv4) dst: Workstation B (IPv4) flow label64 next payload length hops src: Workstation A (IPv4-compatible) dst: Workstation B (IPv4-compatible) payl oad nxt: 41 src: Workstation A (IPv4) dst: Workstation B (IPv4) flow label64 next payload length hops src: Workstation A (I Pv4-compati bl e) dst: Workstation B (I Pv4-compati bl e) payl oad 4 IPv4 Header 4 Chapter 9. IP version 6 385 Figure 9-27 Host-to-host automatic tunneling Configured tunneling Configured tunneling is used for host-router or router-router tunneling of IPv6-over-IPv4. The sending host or the forwarding router is configured so that the route, as well as having a next hop, also has a tunnel end address (which is always an IPv4-compatible address). The process of encapsulation is the same as for automatic tunneling, except that the IPv4 destination address is not derived from the low-order 32 bits of the IPv6 destination address, but from the low-order 32 bits of the tunnel end. The IPv6 destination and source addresses do not need to be IPv4-compatible addresses in this case. When the router at the end of the tunnel receives the IPv4 datagram, it processes it in exactly the same way as a node at the end of an automatic tunnel. When the original IPv6 packet is passed to the IPv6 layer in the router, it recognizes that it is not the destination, and the router forwards the packet on to the final destination as it would for any other IPv6 packet. X Y Ethernet IPv6/IPv4 Router IPv4 Network IPv6/IPv4 Router IPv6/IPv4 Host (2) A IPv6/IPv4 Host (1) B nxt:41 src: Workstation B (IPv4) dst: Workstation A (IPv4) flow label64 next payload length hops src: Workstation B (IPv4-compatible) dst: Workstation A (IPv4-compatible) payload 4 nxt:41 src: Workstation B (IPv4) dst: Workstation A (IPv4) flow label64 next payload length hops src: Workstation B (IPv4-compatible) dst: Workstation A (IPv4-compatible) payload 4 nxt:41 src: Workstation B (IPv4) dst: Workstation A (IPv4) flow label64 next payload length hops src: Workstation B (IPv4-compatible) dst: Workstation A (IPv4-compatible) payload 4 IPv4 Header [...]... applies to wireless LANs and provides 11 Mbps transmission with fallbacks to 5. 5, 2, and 1 Mbps in the 2.4 GHz band 802.11b uses only DSS 802.11b was a 1999 ratification to the original 802.11 standard, allowing wireless functionality comparable to Ethernet 802.11g Applies to wireless LANs and provides 20+ Mbps in the 2.4 GHz band For additional information about the 802.11 family of standards, see: http://www.ieee802.org/11/... to DSL and cable This specification is also known as WirelessMAN Also known as Mobile WiMaX This extends and improves the modulation schemes described in the original/fixed WiMax standard This allows for fixed wireless and mobile NLOS applications by improving upon the Orthogonal Frequency Division Multiple Access (OFDMA) This should not be confused with 802.20 TCP/IP Tutorial and Technical Overview. .. 403 404 TCP/IP Tutorial and Technical Overview Part 2 Part 2 TCP/IP application protocols Included in the TCP/IP suite of protocols is an extensive list of applications designed to make use of the suite's services It is through these entities that resources can be made available, data can be moved between hosts, and remote users can communicate Examples of applications architected within the TCP/IP. .. tunnel-end (router Y) and forwards the datagram over the IPv4 network 3 The IPv4 stack of router Y receives the frame Seeing the Protocol field value of 41, it removes the IPv4 header, and passes the remaining IPv6 packet to its IPv6 stack The IPv6 stack reads the destination IPv6 address, and forwards the packet 4 Workstation B receives the IP6 packet 386 TCP/IP Tutorial and Technical Overview IPv4 Network... obstructing building Figure 10-3 An example of Fresnel zones 394 TCP/IP Tutorial and Technical Overview Line of sight (LOS) and non-line of sight (NLOS) service Line of sight (LOS) and non-line of sight (NLOS) are used to define a link by its position relative to a signal’s transmitter An LOS link is one that must have an unobstructed path between it and the signal’s source, literally meaning that the link... of standards There are several specifications in the 802.11 family of standards: 802.11 Applies to wireless LANs and provides 1 or 2 Mbps transmission in the 2.4 GHz band using either frequency hopping spread spectrum (FHSS) or direct sequence spread spectrum (DSSS) Chapter 10 Wireless IP 397 802.11a An extension to 802.11 that applies to wireless LANs and provides up to 54 Mbps in the 5 GHz band 802.11a... Copyright IBM Corp 1989-2006 All rights reserved 4 05 Protocol, which is defined by the Open Mobile Alliance (OMA) and is defined in specifications created by that organization These OMA specifications are available at: http://www.openmobilealliance.org/tech/affiliates/wap/wapindex.html 406 TCP/IP Tutorial and Technical Overview 11 Chapter 11 Application structure and programming interfaces Application protocols... the ping command Additional information about sockets is in 4.1.2, “Sockets” on page 1 45 Socket APIs provide functions that enable applications to perform the following actions: Initialize a socket Bind (register) a socket to a port address 410 TCP/IP Tutorial and Technical Overview Listen on a socket for inbound connections Accept an inbound connection Connect outbound to a server Send and receive... provider’s hotspot 10 .5. 3 Mesh networking Mesh networking is a method of designing a network such that clients can act as repeaters, and repeaters can sometimes act as clients In theory, this allows each node within a mesh network to be connected to every other node Blocked routes can easily be bypassed, because a datagram can hop from node to node 402 TCP/IP Tutorial and Technical Overview until a new... http://ipv6.internet2.edu 390 TCP/IP Tutorial and Technical Overview 10 Chapter 10 Wireless IP In an increasingly mobile society, the need for wireless connectivity is a consistently growing area As a result, technology is rapidly advancing to provide wireless support for business and personal use This chapter discusses some of the fundamental concepts behind wireless IP and the technology that supports . datagram and the remaining IPv6 packet is then handled by the IPv6 stack. 384 TCP/IP Tutorial and Technical Overview Figure 9-26 Router-to-host automatic tunneling Figure 9-27 on page 3 85 shows. RFC 4303 – IP Encapsulating Security Payload (ESP) (for v6 and v4) (December 20 05) 390 TCP/IP Tutorial and Technical Overview  RFC 26 75 – IPv6 Jumbograms, August 1999)  RFC 2460 – Internet Protocol,. functional conformance and performance testing for implementations of IETF IPv6 standards or RFCs. Interoperability testing is also a key ITS service. 378 TCP/IP Tutorial and Technical Overview 9.7.3