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IP Fragmentation
400px, An example of the fragmentation of a protocol data unit in a given layer into smaller fragments. IP fragmentation is an Internet Protocol (IP) process that breaks packets into smaller pieces (fragments), so that the resulting pieces can pass through a link with a smaller maximum transmission unit (MTU) than the original packet size. The fragments are reassembled by the receiving host. The details of the fragmentation mechanism, as well as the overall architectural approach to fragmentation, are different between IPv4 and IPv6. Process describes the procedure for IP fragmentation, and transmission and reassembly of IP packets. RFC 815 describes a simplified reassembly algorithm. The ''Identification'' field along with the ''foreign'' and ''local internet address'' and the ''protocol ID'', and ''Fragment'' offset field along with ''Don't Fragment'' and ''More Fragments'' flags in the IP header are used for fragmentation and reassembly of IP packets. If a receiving host ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Internet Control Message Protocol
The Internet Control Message Protocol (ICMP) is a supporting protocol in the Internet protocol suite. It is used by network devices, including routers, to send error messages and operational information indicating success or failure when communicating with another IP address, for example, an error is indicated when a requested service is not available or that a host or router could not be reached. ICMP differs from transport protocols such as TCP and UDP in that it is not typically used to exchange data between systems, nor is it regularly employed by end-user network applications (with the exception of some diagnostic tools like ping and traceroute). ICMP for IPv4 is defined in RFC 792. A separate ICMPv6, defined by RFC 4443, is used with IPv6. Technical details ICMP is part of the Internet protocol suite as defined in RFC 792. ICMP messages are typically used for diagnostic or control purposes or generated in response to errors in IP operations (as specified in RFC 1122 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protocol Data Unit
In telecommunications, a protocol data unit (PDU) is a single unit of information transmitted among peer entities of a computer network. It is composed of protocol-specific control information and user data. In the layered architectures of communication protocol stacks, each layer implements protocols tailored to the specific type or mode of data exchange. For example, the Transmission Control Protocol (TCP) implements a connection-oriented transfer mode, and the PDU of this protocol is called a ''segment'', while the User Datagram Protocol (UDP) uses datagrams as protocol data units for connectionless communication. A layer lower in the Internet protocol suite, at the Internet layer, the PDU is called a packet, irrespective of its payload type. Packet-switched data networks In the context of packet switching data networks, a protocol data unit (PDU) is best understood in relation to a service data unit (SDU). The features or services of the network are implemented in disti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IP Fragmentation Attack
IP fragmentation attacks are a kind of computer security attack based on how the Internet Protocol (IP) requires data to be transmitted and processed. Specifically, it invokes IP fragmentation, a process used to partition messages (the service data unit (SDU); typically a packet) from one layer of a network into multiple smaller payloads that can fit within the lower layer's protocol data unit (PDU). Every network link has a maximum size of messages that may be transmitted, called the maximum transmission unit (MTU). If the SDU plus metadata added at the link layer exceeds the MTU, the SDU must be fragmented. IP fragmentation attacks exploit this process as an attack vector. Part of the TCP/IP suite is the Internet Protocol (IP) which resides at the Internet Layer of this model. IP is responsible for the transmission of packets between network end points. IP includes some features which provide basic measures of fault-tolerance (time to live, checksum), traffic prioritizati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Packet Loss
Packet loss occurs when one or more packets of data travelling across a computer network fail to reach their destination. Packet loss is either caused by errors in data transmission, typically across wireless networks, or network congestion.Kurose, J.F. & Ross, K.W. (2010). ''Computer Networking: A Top-Down Approach''. New York: Addison-Wesley. Packet loss is measured as a percentage of packets lost with respect to packets sent. The Transmission Control Protocol (TCP) detects packet loss and performs retransmissions to ensure reliable messaging. Packet loss in a TCP connection is also used to avoid congestion and thus produces an intentionally reduced throughput for the connection. In real-time applications like streaming media or online games, packet loss can affect a user's quality of experience (QoE). Causes The Internet Protocol (IP) is designed according to the end-to-end principle as a best-effort delivery service, with the intention of keeping the logic routers mus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Out-of-order Delivery
In computer networking, out-of-order delivery is the delivery of data packets in a different order from which they were sent. Out-of-order delivery can be caused by packets following multiple paths through a network, by lower-layer retransmission procedures (such as automatic repeat request), or via parallel processing paths within network equipment that are not designed to ensure that packet ordering is preserved. One of the functions of TCP is to prevent the out-of-order delivery of data, either by reassembling packets in order or requesting retransmission of out-of-order packets. See also * Packet loss * Selective ACK * IP fragmentation * Head-of-line blocking Head-of-line blocking (HOL blocking) in computer networking is a performance-limiting phenomenon that occurs when a line of packets is held up in a queue by a first packet. Examples include input buffered network switches, out-of-order delivery a ... External links * RFC 4737, ''Packet Reordering Metrics'', A. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Traffic Flow (computer Networking)
In packet switching networks, traffic flow, packet flow or ''network flow'' is a sequence of packets from a source computer to a destination, which may be another host, a multicast group, or a broadcast domain. RFC 2722 defines traffic flow as "an artificial logical equivalent to a call or connection." RFC 3697 defines traffic flow as "a sequence of packets sent from a particular source to a particular unicast, anycast, or multicast destination that the source desires to label as a flow. A flow could consist of all packets in a specific transport connection or a media stream. However, a flow is not necessarily 1:1 mapped to a transport connection." Flow is also defined in RFC 3917 as "a set of IP packets passing an observation point in the network during a certain time interval." Packet flow temporal efficiency can be affected by one-way delay (OWD) that is described as a combination of the following components: * Processing delay (the time taken to process a packet in a network ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hash Function
A hash function is any function that can be used to map data of arbitrary size to fixed-size values. The values returned by a hash function are called ''hash values'', ''hash codes'', ''digests'', or simply ''hashes''. The values are usually used to index a fixed-size table called a ''hash table''. Use of a hash function to index a hash table is called ''hashing'' or ''scatter storage addressing''. Hash functions and their associated hash tables are used in data storage and retrieval applications to access data in a small and nearly constant time per retrieval. They require an amount of storage space only fractionally greater than the total space required for the data or records themselves. Hashing is a computationally and storage space-efficient form of data access that avoids the non-constant access time of ordered and unordered lists and structured trees, and the often exponential storage requirements of direct access of state spaces of large or variable-length keys. Use of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cisco Express Forwarding
{{Short description, Layer 3 switching technology Cisco Express Forwarding (CEF) is an advanced layer 3 switching technology used mainly in large core networks or the Internet to enhance the overall network performance. Although CEF is a Cisco proprietary protocol other vendors of multi-layer switches or high-capacity routers offer a similar functionality where layer-3 switching or routing is done in hardware (in an ASIC) instead of by software and the (central) CPU. Function CEF is mainly used to increase packet switching speed by reducing the overhead and delays introduced by other routing techniques. CEF consists of two key components: The Forwarding Information Base (FIB) and adjacencies. The FIB is similar to the routing table generated by multiple routing protocols, maintaining only the next-hop address for a particular IP-route. The adjacency table maintains layer 2 or switching information linked to a particular FIB entry, avoiding the need for an Address Resolution Pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Link Aggregation
In computer networking, link aggregation is the combining ( aggregating) of multiple network connections in parallel by any of several methods, in order to increase throughput beyond what a single connection could sustain, to provide redundancy in case one of the links should fail, or both. A link aggregation group (LAG) is the combined collection of physical ports. Other umbrella terms used to describe the concept include trunking, bundling, bonding, channeling or teaming. Implementation may follow vendor-independent standards such as Link Aggregation Control Protocol (LACP) for Ethernet, defined in IEEE 802.1AX or the previous IEEE 802.3ad, but also proprietary protocols. Motivation Link aggregation increases the bandwidth and resilience of Ethernet connections. Bandwidth requirements do not scale linearly. Ethernet bandwidths historically have increased tenfold each generation: 10 megabit/s, 100 Mbit/s, 1000 Mbit/s, 10,000 Mbit/s. If one started to bump in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Path MTU Discovery
Path MTU Discovery (PMTUD) is a standardized technique in computer networking for determining the maximum transmission unit (MTU) size on the network path between two Internet Protocol (IP) hosts, usually with the goal of avoiding IP fragmentation. PMTUD was originally intended for routers in Internet Protocol Version 4 (IPv4). However, all modern operating systems use it on endpoints. In IPv6, this function has been explicitly delegated to the end points of a communications session. As an extension to the standard path MTU discovery, a technique called ''Packetization Layer Path MTU Discovery'' works without support from ICMP. Implementation For IPv4 packets, Path MTU Discovery works by setting the ''Don't Fragment'' (DF) flag bit in the IP headers of outgoing packets. Then, any device along the path whose MTU is smaller than the packet will drop it, and send back an Internet Control Message Protocol (ICMP) ''Fragmentation Needed'' (Type 3, Code 4) message containing its MTU, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Router (computing)
A router is a networking device that forwards data packets between computer networks. Routers perform the traffic directing functions between networks and on the global Internet. Data sent through a network, such as a web page or email, is in the form of data packets. A packet is typically forwarded from one router to another router through the networks that constitute an internetwork (e.g. the Internet) until it reaches its destination node. A router is connected to two or more data lines from different IP networks. When a data packet comes in on one of the lines, the router reads the network address information in the packet header to determine the ultimate destination. Then, using information in its routing table or routing policy, it directs the packet to the next network on its journey. The most familiar type of IP routers are home and small office routers that simply forward IP packets between the home computers and the Internet. More sophisticated routers, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
