J. Postel and J. Reynolds, File Transfer Protocol (FTP), Internet Request for Comments RFC 765, Oct. 1985.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....indeed quite similar to the basic ARP REQUEST behavior, except that a mobile node may answer the ROUTEREQUEST from its cache,whereas ARPREQUESTS are normally only answered by the target node itself. With ARP, in cases in which several LANs have been bridged together, the bridge may run proxy ARP [Postel 1984], which allows the bridge to answer an ARP REQUEST on behalf of another node (behind the bridge) In this sense, our nonpropagating ROUTE REQUESTS are also similar to proxy ARP; they expand the effective size of a single node s Route Cache by allowing it to cheaply make use of the caches of ....

J. B. Postel. Multi-LAN Address Resolution. Internet Request For Comments RFC 925, October 1984.

....has not yet been implemented. 4.4. 4 IP networks The APA provides the UDPNetwork class to support meta machines comprising machines connected by a network supporting the User Datagram Protocol (UDP) 83] 84] 85] UDP is a user level interface to the underlying Internet Protocol (IP) [86], an unreliable datagram protocol. The UDPNetwork class layers on top of the UDP protocol a reliability and fragmentation protocol, both required because the UDP protocol is unreliable and has a packet length limitation of 64,000 bytes. In contrast, the Transmission Control Protocol (TCP) 87] ....

"User datagram protocol," Internet Request For Comments RFC-791, Sept. 1981. Available as ftp://ds.internic.net/rfc791.txt.

....selection is a choice between extremes. For example, in the Internet protocol suite we note that the service provided by Transmission Control Protocol (TCP) 10] is ordered, reliable (no loss) discards duplicates and is flow controlled, while the service provided by User Datagram Protocol (UDP)[11] is unordered, unreliable (lossy) may deliver duplicates, and is not flowcontrolled. The fact that these protocols provide service at the extremes of each of these four QoS axes creates a dilemma for the designer of an application whose needs reside in the middle. When designing an application ....

J.B. Postel. User Datagram Protocol. Internet Request for Comments RFC768, Aug 1981.

....previous mobile host protocols, and Section 8 presents conclusions. 2. Overview In the IP addressing scheme, the IP network number for a network is assigned by a central authority (the Internet Assigned Numbers Authority) to an organization requesting connection of its network to the Internet [Reynolds 92] The assignment of host numbers within that network number is then delegated to the requesting organization. Mobile hosts owned by that organization should be assigned a permanent IP address within that network number. The mobile host will use this IP address whether attached to its home ....

J. K. Reynolds and J. B. Postel. Assigned numbers. Internet Request For Comments RFC 1340, July 1992.

....with the real physical network address for the mobile host, rather than the physical address of the home gateway which they may still have in their cache. While a mobile host is disconnected from its home network, the home gateway also answers ARP requests for the mobile host with proxy ARP [Postel 84] 5. Locating a Mobile Host When sending an IP datagram to a mobile host M, if the sender has no cached knowledge of the current location of M, the datagram will be routed to M s home network using the standard routing algorithms of IP. The datagram will thus reach the home gateway of M, which ....

J. B. Postel. Multi-LAN address resolution. Internet Request For Comments RFC 925, October 1984.

....now widely available and affordable, and the distinction between desktop and portable computers is beginning to disappear in terms of both features and computational power. However, these mobile hosts cannot currently interoperate easily or conveniently with internetworking protocols such as IP [Postel 81b] due to the operation of existing internetwork addresses and routing algorithms. For example, in IP, host addresses are composed of a network number, identifying the network to which the host is attached, and a host number, identifying the particular host within that network. IP expects to be ....

....network to the mobile host is put on the individual gateway that understands the particular physical network to which the mobile host is currently connected. 3. Datagram Routing and Delivery Datagram routing and delivery to mobile hosts is done using the standard IP loose source routing option [Postel 81b] This section reviews the operation of the IP loose source routing option and then discusses its use in mobile host IP datagram delivery. Special support is required only in sending datagrams to a mobile host; sending datagrams from a mobile host requires no special support in any host or ....

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J. B. Postel, editor. Internet Protocol. Internet Request For Comments RFC 791, September 1981.

....discovered. 3.1. Route Discovery A very simple and efficient method of route discovery suitable for use directly in some ad hoc networks is the Internet s Address Resolution Protocol (ARP) 11] ARP is designed for dynamically translating a host s network protocol address (such as an IP address [12]) to its MAC level address (such as an Ethernet address) A host attempting to translate another host s address broadcasts a query packet onto its local network, which is answered by the target host giving its MAC address; other hosts on the local network receiving the query do not reply. The ....

J. B. Postel, editor. Internet Protocol. Internet Request For Comments RFC 791, September 1981.

....MC68020 processor and an AMD Am7990 LANCE Ethernet network controller. The implementation uses an RPC packet protocol similar to Cedar RPC [3] except that a blast protocol [20] is used for multi packet messages. The RPC protocol is layered directly on top of the IP Internet datagram protocol [13]. In this implementation, the measured latency for a null RPC with no arguments or return values between two user level threads executing on separate Sun 3 60 workstations on the Ethernet is 573 microseconds. This time compares well with the fastest null network RPC times reported in the ....

....by virtual address, saving the expense of reloading the entire TLB after a global flush. Similarly, the MIPS MMU [9] allows the operating system to individually modify any specified TLB entry. 4.2. The Packet Header The Peregrine RPC protocol is layered directly on top of the Internet IP protocol [13], which in our current implementation is layered directly on top of Ethernet packets. Figure 1 shows the IP and Peregrine RPC packet headers. In the RPC header, the packet type is either call or return. The call sequence number identifies separate RPCs from the same client, whereas the packet ....

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J.B. Postel. Internet Protocol. Internet Request For Comments RFC 791, September 1981.

....but we must ensure that hosts that do not have physical access to data or management packets sent to or from the mobile host cannot corrupt such packets. 3. Definitions The following specific terms are used in this paper: Node. A device in the network that implements the Internet Protocol, IP [11]. Router. A node that forwards IP datagrams, as specified in [2] This does not include nodes that, though capable of IP forwarding, have that capability turned off, nor does it include nodes that perform IP forwarding only in processing IP Source Route options. Host. Any node that is not a ....

J. B. Postel. Internet Protocol. Internet Request For Comments RFC 791, September 1981.

....cache with the real physical network address for the mobile host, rather than the physical address of the home agent that they may still have in their caches. While a mobile host is disconnected from its home network, the home agent also answers ARP requests for the mobile host with proxy ARP [12]. As described above, a home agent must be present on each IP network (or subnet) having hosts that may become mobile, and a foreign agent must likewise be present on each IP network (or subnet) to which mobile hosts may connect. The home agent can then intercept IP packets for a mobile host ....

J. B. Postel. Multi-LAN address resolution. Internet Request For Comments RFC 925, October 1984.

....from one location to another; or it may simply be disconnected from the network at its current location, temporarily moved to a new location, and reconnected to the network through either a wireless or conventional wired network interface. However, current internetworking protocols, including IP [10], ISO CLNP [14] NetWare IPX [20] and AppleTalk [15] require mobile hosts to change their network addresses when moving to a new network, making host movement inconvenient and error prone. The This research was supported in part by the Advanced Research Projects Agency under Contract ....

....is no penalty for a host being mobile capable, since the protocol automatically uses only the standard internetwork routing mechanisms and adds no overhead when a host is currently connected to its home network. This paper concentrates on the design of MHRP as it applies to the Internet using IP [10]. Section 2 describes the MHRP infrastructure. Section 3 describes the protocol used when a mobile host moves to a new network, and Section 4 describes the mechanism used for IP packet routing and delivery to mobile hosts. The features introduced in MHRP for robustness are discussed in Section 5. ....

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J. B. Postel, editor. Internet Protocol. Internet Request For Comments RFC 791, September 1981.

....a new encapsulation protocol. The home agent or initial cache agent handling the packet transforms it into a new IP packet, addressed to the foreign agent, by adding a new header (the MHRP header) to the packet between the IP header and any existing transport level header such as TCP [11] or UDP [8], as illustrated in Figure 2. Once the MHRP header is added, the packet uses only normal IP routing for delivery to the foreign agent. This use of encapsulation is known as tunneling. Once received by the foreign agent, the MHRP header is removed from the packet, the original IP header is ....

J. B. Postel. User Datagram Protocol. Internet Request For Comments RFC 768, August 1980.

....MC68020 processor and an AMD Am7990 LANCE Ethernet network controller. The implementation uses an RPC packet protocol similar to Cedar RPC [3] except that a blast protocol [20] is used for multi packet messages. The RPC protocol is layered directly on top of the IP Internet datagram protocol [13]. In this implementation, the measured latency for a null RPC with no arguments or return values between two user level threads executing on separate Sun 3 60 workstations on the Ethernet is 573 microseconds. This time compares well with the fastest null network RPC times reported in the ....

....by virtual address, saving the expense of reloading the entire TLB after a global flush. Similarly, the MIPS MMU [9] allows the operating system to individually modify any specified TLB entry. 4. 2 The Packet Header The Peregrine RPC protocol is layered directly on top of the Internet IP protocol [13], which in our current implementation is layered directly on top of Ethernet packets. Figure 1 shows the IP and Peregrine RPC packet headers. In the RPC header, the packet type is either call or return. The Procedure number Call sequence number IP header checksum Packet sequence number RPC ....

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J.B. Postel. Internet Protocol. Internet Request For Comments RFC 791, September 1981.

....reboots of the Location Server. When the Location Server receives notification that a mobile host is disconnecting from its home network, the Location Server also arranges to intercept any IP packets sent to the mobile host over the home network. This may be done, for example, with proxy ARP [7]. When the old Base Station receives notification that a mobile host is disconnecting, the old Base Station normally caches a forwarding pointer to the new Base Station s IP address by becoming a Location Cache for this mobile host. This forwarding pointer is only a cache, though, and is ....

J. B. Postel. Multi-LAN address resolution. Internet Request For Comments RFC 925, October 1984.

....Pittsburgh, PA 15213 3891 dbj cs.cmu.edu dbj cs.cmu.edu 1. Introduction With the increasing popularity of notebook and palmtop computers and the increasing availability of wireless networking interfaces such as radio and infrared, there is currently a great deal of interest in providing IP [6] networking support for mobile hosts in the Internet [1, 2, 3, 4, 9, 10, 11] However, IP host addresses are composed of a network number, identifying the network to which the host is attached, and a host number, identifying the particular host within that network; IP expects to be able to route ....

J. B. Postel, editor. Internet Protocol. Internet Request For Comments RFC 791, September 1981.

....somewhat similar to our nonpropagating route request packets, except that a mobile host may answer the route request from its cache whereas ARP requests are normally only answered by the target host itself. In cases in which several LANs have been bridged together, the bridge may run proxy ARP [24], which allows the bridge to answer an ARP request on behalf of another host. In this sense, our nonpropagating route requests are also similar to proxy ARP in that they expand the effective size of a single host s route cache by allowing it to cheaply make use of the caches of neighboring hosts ....

J. B. Postel. Multi-LAN address resolution. Internet Request For Comments RFC 925, October 1984.

....header, identifying each forwarding hop by the address of the next node to which to transmit the packet on its way to the destination host. Source routing has been used in a number of contexts for routing in wired networks, using either statically defined or dynamically constructed source routes [4, 5, 12, 20, 22, 28], and has been used with statically configured routes in the Tucson Amateur Packet Radio (TAPR) work for routing in a wireless network [14] The protocol presented here is explicitly designed for use in the wireless environment of an ad hoc network. There are no periodic router advertisements in ....

J. B. Postel, editor. Internet Protocol. Internet Request For Comments RFC 791, September 1981.

....each process, and the overhead of garbage collection. 5.3 Communication Protocols Rollback recovery complicates the implementation of protocols used for interprocess communications. Some protocols offer the abstraction of reliable communication channels such as connection based protocols like TCP [139] or RPC style communications [27] Alternatively, other protocols offer the abstraction of an unreliable datagram service such as UDP [139] Each type of abstraction requires additional support to operate properly across failures and recoveries. 5.3.1 Location Independent Identities and ....

....used for interprocess communications. Some protocols offer the abstraction of reliable communication channels such as connection based protocols like TCP [139] or RPC style communications [27] Alternatively, other protocols offer the abstraction of an unreliable datagram service such as UDP [139]. Each type of abstraction requires additional support to operate properly across failures and recoveries. 5.3.1 Location Independent Identities and Redirection For all communication protocols, a rollback recovery system must mask the actual identity and location of a process or a remote port ....

J. B. Postel. Internet Protocol. Internet Request For Comments RFC 791, September 1981.

....We have implemented our threads interface with Pthreads [18] a POSIX conformant, user space threads implementation. We have extended the kernels of our SPARC workstations with IP multicast, a kernel extension for multicasting [13] Point to point message passing has been implemented on top of UDP [21]. Pthreads provides all the functionality we need, including priority scheduling, and runs entirely in user space. User space threads are more efficient than (pure) kernel based implementations, because thread context switches do not involve trapping to the kernel. However, they suffer from poor ....

J. Postel. User Datagram Protocol. Internet Request for Comments RFC768, September 1981.

....foreign agent, the original IP header is reconstructed and the tunneling header is removed, and the packet is transmitted locally to the mobile host. Although more efficient than IP in IP encapsulation, the minimal encapsulation protocol cannot be used with IP packets that have been fragmented [27], since the tunneling header does not provide a means to indicate that the original packet was a fragment. All registrations of a mobile host with its home agent must be authenticated, in order to guard against malicious forged registrations. Without authentication, an attacker could register a ....

J. B. Postel, editor. Internet Protocol. Internet Request For Comments RFC 791, September 1981.

....already support reliable and sequenced data delivery, in most cases this is via the use of virtual circuits for the projected use of PVM, the overheads and scalability limitations of using such a service directly did not warrant its adoption. In the test implementations of PVM, the UDP [11] protocol was used; this deliberate choice of a simple datagram protocol also permits relatively simple porting or protocol conversion when PVM is to be installed under a different operating system environment. Across the network, pvmd processes communicate using UDP datagrams. The well known ....

J. B. Postel, User Datagram Protocol, Internet Request for Comments RFC-768, August 1980.

....home agent acts to forward all packets for the mobile host to its current location for delivery locally to the mobile host. Packets addressed to the mobile host that appear on the mobile host s home network must be intercepted by the mobile host s home agent, for example by using proxy ARP [24] or through cooperation with the local routing protocol in use on the home network. For each such packet intercepted, the home agent tunnels the packet to the mobile host s current care of address. If the care of address is provided by a foreign agent, the foreign agent removes any tunneling ....

J. B. Postel. Multi-LAN address resolution. Internet Request For Comments RFC 925, October 1984.

....increases in portability and ease of network access, it becomes natural for users to expect to be able to access the Internet at any time and from anywhere, and to transparently remain connected and continue to use the network as they move about. However, internetworking protocols such as IP [23] used in the Internet do not currently support host mobility. A mobile user, today, must generally change IP A version of this paper will appear as a chapter in the book Mobile Computing, edited by Tomasz Imielinski and Hank Korth, Kluwer Academic Publishers, 1996. A version of this paper will ....

....optimizing packet routing to mobile hosts. Section 5 discusses the scalability of this work to very large numbers of mobile hosts, and Section 6 presents conclusions. 2. Problem Analysis 2.1. Internetwork Routing In order to provide scalable routing support, internetworking protocols such as IP [23], ISO CLNP [27] NetWare IPX [33] and AppleTalk [28] use hierarchical addressing and routing schemes. For example, in IP, the network address of a host is divided into two levels of hierarchy: a network number identifying the network to which the host is connected, and a host number identifying ....

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J. B. Postel, editor. Internet Protocol. Internet Request For Comments RFC 791, September 1981.

....LEO satellites and ground stations. My responsibility in this group is to implement several features for PIX to enhance its functionality, while the other members are working on the implementation of protocols, such as Simple Network Management Protocol (SNMP) 26] File Transfer Protocol (FTP) [27], Satellite Transport Protocol (STP) 28] Dynamic Source Routing (DSR) 29] IPv6 [30] and a wireless LAN driver. The previous version of PIX does not have the support for server functionality. The implemented components can only be manually assembled. There is only a simple event manager ....

J. Postel and J. Reynolds, File Transfer Protocol (FTP), Internet Request for Comments RFC 765, Oct. 1985.

No context found.

J.B. Postel. User Datagram Protocol. Internet Request for Comments RFC768, Aug 1981.

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