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Topic: Classless interdomain routing

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	Border Gateway Protocol - Wikipedia, the free encyclopedia
		BGP supports classless interdomain routing and uses route aggregation to decrease the size of routing tables.
		With damping, a route's flapping is exponentially decayed.
		If the global routing table grows to the point where some older, less capable, routers cannot cope with the memory requirements or the CPU load of maintaining the table, these routers will cease to be effective gateways between the parts of the Internet they connect.
	www.wikipedia.org /wiki/BGP (1173 words)

	Advanced IP Routing in Cisco Networks:Classless Routing (Site not responding. Last check: 2007-10-11)
		Classless routing protocols, however, propagate the mask with the route in routing updates.
		The one that is typically used in classless routing table lookups is call the patricia tree algorithm (Gonnet and Baeza-Yates 1991 or Sedgewick 1988).
		As we’ve seen, the reason that classless routing works is that each route and its mask (also called a prefix mask or just a prefix) is propagated throughout the network.
	www.wanguy.com /resources/cisco/training/adviprouting/ch05/05-01.html (1113 words)

	Chapter 3 - Linux Policy Routing Structure: Policy Routing with Linux by Matthew G. Marsh
		In a single routing table system, such as current network router devices, or most operating systems, all of the routes specified are in a single group called a table.
		The routing table in the kernel is kept in a data structure that allows the final result to be achieved with minimal cost.
		Route maps are used to set as many policy actions as you like based on the match conditions.
	www.policyrouting.org /PolicyRoutingBook/ONLINE/CH03.web.html (6325 words)

	[No title]
		Note that during failures, partial routing of traffic to a site which takes its address space from one service provider but which is actually reachable only through another (i.e., the case of a site which has change service providers) may occur because such traffic will be routed along the path advertised by the aggregated route.
		Note that handling of the "default" route (0.0.0.0/0.0.0.0) is a special case of this rule - a network must not follow the default to destinations which are part of one of it's aggregated advertisements.
		This block is described by the route 192.24.34.0, mask 255.255.254.0 Note that if the network provider uses an IGP which can support classless networks, he can (but doesn't have to) perform "supernetting" at the point where he connects to his clients and therefore only maintain six distinct routes for the 36 class C network numbers.
	www.ietf.org /rfc/rfc1519.txt (6630 words)

	RFC 1771 (rfc1771) - A Border Gateway Protocol 4 (BGP-4)
		Each such route is identified by its destination (expressed as an IP prefix), which unambiguously identifies the route in the context of the BGP speaker - BGP speaker connection to which it has been previously been advertised.
		Route selection then consists of individual application of the degree of preference function to each feasible route, followed by the choice of the one with the highest degree of preference.
		If the route is learned from a BGP speaker in the local autonomous system, either the value of the LOCAL_PREF attribute shall be taken as the degree of preference, or the local system shall compute the degree of preference of the route based on preconfigured policy information.
	www.faqs.org /rfcs/rfc1771.html (14132 words)

	Classless inter-domain routing : Classless interdomain routing
		Classless Inter-Domain Routing (CIDR) using variable length subnet masks (VLSM) was created to allow for greater flexibility with routed IP networks, to allow for the accelerating expansion of the Internet.
		Another purpose of CIDR was the possibility of routing prefix aggregation: for example, sixteen contiguous /24 networks could now be aggregated together, and advertised to the outside world as a single /20 route.
		This allowed a significant reduction in the number of routes that had to be advertised over the Internet, preventing 'routing table explosion' from overwhelm routers and stopping the Internet from expanding further.
	www.termsdefined.net /cl/classless-interdomain-routing.html (688 words)

	Classless Inter-Domain Routing CIDR - Internet Encyclopedia - eLook.org
		Faced with exhaustion of class B address space and the explosion of routing table growth triggered by a flood of new class Cs, IETF began implementing Classless Interdomain Routing (CIDR), in the early 1990s.
		The primary requirement for CIDR is the use of routing protocols that support it, such as RIP Version 2, OSPF Version 2, and BGP Version 4.
		A route is no longer an IP address, broken down into network and host bits according to its class.
	www.elook.org /internet/25.html (210 words)

	Classless inter-domain routing : Classless interdomain routing (Site not responding. Last check: 2007-10-11)
		Without any other way of specifying the length of a subnet mask, routing protocols necessarily used the class of the IP address specified in route advertisements to determine the size of the routing prefixes to be set up in the routing tables.
		Classless routing came into use in the mid 1990s due to the inefficiences of the classful system.
		It uses material from the wikipedia article Classless inter-domain routing : Classless interdomain routing.
	www.eurofreehost.com /cl/Classless_interdomain_routing.html (403 words)

	CIDR - a Whatis.com definition - see also: Classless Inter-Domain Routing
		CIDR (Classless Inter-Domain Routing, sometimes known as supernetting) is a way to allocate and specify the Internet addresses used in inter-domain routing more flexibly than with the original system of Internet Protocol (IP) address classes.
		A destination IP address or route that describes many possible destinations has a shorter prefix and is said to be less specific.
		CIDR lets one routing table entry represent an aggregation of networks that exist in the forward path that don't need to be specified on that particular gateway, much as the public telephone system uses area codes to channel calls toward a certain part of the network.
	www.whatis.com /definition/0,289893,sid9_gci213850,00.html (597 words)

	RFC 1519 (rfc1519) - Classless Inter-Domain Routing (CIDR): an Address Ass
		Also, since the routing cost associated with assigning a multi-homed site out of a service provider's address space is no greater than the current method of a random allocation by a central authority, it makes sense to allocate all address space out of blocks assigned to service providers.
		To take advantage of aggregation of routing information, however, it is necessary that the capability to represent routes as arbitrary network and mask fields (as opposed to the current class A/B/C distinction) be added to the common Internet inter-domain routing protocol(s).
		Under the proposed plan, growth of the routing table in a default- free router is greatly reduced since most new address assignment will come from one of the large blocks allocated to the service providers.
	www.faqs.org /rfcs/rfc1519.html (6557 words)

	CDIR: Classless Interdomain Routing (Site not responding. Last check: 2007-10-11)
		Classless Interdomain Routing (also called supernetting) is a way to prevent an explosion in the size of the Internet routing tables.
		The routing tables and routing algorithms must be extended to base their routing decisions on a 32-bit address and a 32-bit mask.
		In countries other than Europe a single routing table entry with an IP address of 0x2000000 and a 32-bit mask of 0xfe000000 (254.0.0.0) could be used to route all of these 65535 network IDs to a single point.
	www.vorlesungen.uos.de /informatik/networking-programming/notes/06Dec96/10.html (325 words)

	Classless Interdomain Routing (CIDR) (Site not responding. Last check: 2007-10-11)
		Also known as supernetting, Classless Interdomain Routing (CIDR) can be used to consolidate several class C network addresses into one logical network.
		), therefore reducing the routing table entries from three to one:
		When routing decisions are made, only the bits covered by the subnet mask are used, thus making these addresses all appear to be part of the same network for routing purposes.
	www.research.umbc.edu /~zhou/windows/tcpip/supernet-example.html (184 words)

	Classless InterDomain Routing (CIDR)
		Classless InterDomain Routing (CIDR) allows a block of IP addresses to be divided to accommodate the needs of networks more flexibly than the class system developed at the inception of the Internet.
		Cost, in the sense of routing, is a determination of the number of routers the information must pass through, and the speed of transmission to the next router, also called a hop, in the route.
		It further conserves routing resources by use of static routes, and by using ARP-like protocols in an environment where the cost metrics are much lower (often a single hop).
	www.sluug.org /resources/cidr.html (1695 words)

	Cisco - IP Addressing and Subnetting for New Users
		These terms are rarely used in the industry anymore because of the introduction of classless interdomain routing (CIDR).
		Classless Interdomain Routing (CIDR) was introduced to improve both address space utilization and routing scalability in the Internet.
		It was needed because of the rapid growth of the Internet and growth of the IP routing tables held in the Internet routers.
	www.cisco.com /warp/public/701/3.html (2654 words)

	IP Addresses
		Classless interdomain routing (CIDR) is an addressing scheme that employs supernet addresses to represent multiple IP destinations.
		Rather than advertise a separate route for each destination in a supernet, a router can use a supernet address to advertise a single route -- called an aggregate route -- that represents all of the destinations.
		This reduces the size of the routing tables used to store advertised IP routes.
	www25.nortelnetworks.com /library/tpubs/html/router/soft1100/114065A/J_12.HTM (1154 words)

	IP Routing Primer: Part Five \| Full Story \| December 4, 2000
		This is known as CIDR (Classless Interdomain Routing).
		As a routing advertisement passes through an AS, it prepends (adjusts the path length advertised) the ASN of the origin AS to the path of other ASes it has traversed.
		BGP routing can also be controlled through the community attribute that puts a predefined code on a group or community of routes so the receiving router takes a predefined action based on the value of that code.
	www.nwc.com /netdesign/1124iprpart5.html (1829 words)

	Subnetting and Classless Interdomain Routing
		The result of using a range of class C addresses is a routing table explosion problem: a class B network of 3000 hosts requires one routing table entry, whereas the same network if it was addressed as a range of class C networks would require 16 entries.
		To overcome the routing table explosion problem, a scheme known as Classless Interdomain Routing (CIDR or ``supernetting'') is used to implement address assignment.
		As the main purpose of CIDR is to reduce the size of the routing tables for the Internet, these documents will not usually be of interest to you unless you are a service provider or you maintain Internet routing tables on your system.
	uw713doc.sco.com /en/NET_tcpip/_cidr.html (520 words)

	History (Site not responding. Last check: 2007-10-11)
		That is why many newly connected organizations ended up with several class C networks, because there were many left of them, which in turn caused a routing table overflow on some devices, because one entry for every single class A, B or C network, respectively, was needed.
		The goal of CIDR was to reduce routing entries in the backbone routers, which began to overflow due to the huge number of entries needed for class C networks (up to about 2 million).
		CIDR served as a short term solution for the routing table problem, and therefore also for the problem of address depletion, because now the many class C networks were available for use.
	www.suse.com /~mha/linux-ip-nat/diplom/node3.html (1377 words)

	Classless InterDomain Routing
		Classless Inter-Domain Routing (CIDR) is a replacement for the old process of assigning Class A, B and C addresses with a generalized network "prefix".
		With the introduction of CIDR address assignments and route aggregation, with a few exceptions, the recommended source for address assignments is your ISP.
		There are still significant global routing table issues and the smaller your network is, the greater your risk is of being dropped from the global routing tables.
	www.netstartechnologies.net /cidr.html (1182 words)

	70-240 in 15 minutes a week: Windows 2000 Routing
		Quite simply, a routed protocol is one whose traffic has an addressing scheme that allows it to be routed, such as IP or IPX.
		Note that the routing table for the system can be viewed either by using the 'Show IP Routing tab option shown above, or by using the route print command from the command prompt.
		Note that the default destination network, 0.0.0.0 is used to route packets to networks not found in the table, usually to the configured default gateway.
	www.serverwatch.com /tutorials/article.php/1472891 (1700 words)

	Zvon - RFC 1519 [Classless Inter-Domain Routing (CIDR): an Address Assignment and Aggregation Strategy] - Cost-benefit ...
		This new method of assigning address through service providers can be put into effect immediately and will, from the start, have the benefit of distributing the currently centralized process of assigning new addresses.
		There are two benefits to be had by deploying this plan: o The current problem with depletion of the available class B address space can be ameliorated by assigning more- appropriately sized blocks of class C's to mid-sized organizations (in the 200-4000 host range).
		As of Jan '92, a default-free routing table (for example, the routing tables maintained by the routers in the NSFNET backbone) contained approximately 4700 entries.
	www.zvon.org /tmRFC/RFC1519/Output/chapter3.html (1246 words)

	ELX.com.au (Australia) - Internet Routing Architectures 2/e, Sam Halabi - ISBN 157870233X (Site not responding. Last check: 2007-10-11)
		You will also learn to control expansion of interior routing protocols using BGP-4, design sound and stable networks, configure the required policies using Cisco IOS Software, and explore routing practices and rules on the Internet.
		Master the addressing techniques - including Classless Interdomain Routing (CIDR) - that are demanded today to facilitate the Internet's rapid and continuing growth.
		Mr Halabi is an expert in complex routing protocols and has specialised in the design of large-scale IP networks.
	www.elx.com.au /item/CI233X (348 words)

	ProQuest Information and Learning - Internet Routing Architectures, Second Edition
		It is written to address real routing issues, using real scenarios, in a comprehensive and accessible manner.
		Internet Routing Architectures is an authoritative text on BGP in theory and practice, covering everything from good design of BGP-based internetworks to actual implementation of those internetworks on Cisco Systems routers.
		However, every ISP backbone routing engineer should have this book with him and use it as a dictionary in case of.
	proquest.safaribooksonline.com /157870233X (913 words)

	ProQuest Information and Learning - IP Routing Fundamentals
		IP Routing Fundamentals provides a detailed examination of routers and the common routing protocols.
		IP Routing Fundamentals is the definitive introduction to routing in IP networks.
		Part I discusses the many roles routers play in networks, Part II talks about the inner working of routers, Part III works with the operational issues of routing protocols, and Part IV addresses implementation issues that provide practical insight, in addition to a discussion of the future of routing.
	proquest.safaribooksonline.com /157870071X (792 words)

	Siemens Communications Lexicon - automatic baud rate detection (ABR)
		This technique allows grouping of IP addresses, where a block of contiguous Class C IP addresses is treated like a separate network.
		The CIDR approach reduces the routing tables stored by routers to a prefix in the IP address.
		This prefix allows large-scale Internet Service Providers or network operators to identify major sections of the Internet, and thus collate underlying networks; this is referred to as supernetting.
	networks.siemens.com /communications/lexicon/0/f008380.htm (136 words)

	[20040326] CCNP 2.0: ROUTING EXAM 640-503
		Each chapter configures one or more routers in a logical way such that even without the use of a physical router to practice on, you should be able to see the results of all the actions.
		The material required for the Routing 2.0 test includes many advanced features of the Cisco environment, most notably routing protocols.
		Three tests, Routing (640-503, for which this book was written), Switching (640-504), and Remote Access (640-505) can all be taken individually at $100 each, or can be combined into a large test called the Foundation (640-509) for $200.
	protocol.ticmundi.com /0-13-090306-X.html (1454 words)

	367: Border Gateway Protocol (BGP) Interdomain Routing
		The continuing proliferation of traffic across today’s networks demands the deployment of an efficient and robust means of data transmission.
		BGP is increasingly deployed across many commercial networks to facilitate routing and information exchange.
		Following the completion of this course you will be able to install, configure and maintain BGP with confidence thus ensuring the effective exchange of data across reliable and robust networks.
	www.lever.co.uk /courses/367.htm (479 words)

	CIDR -- Classless InterDomain Routing
		The reason for this is the ever-growing size of the internet routing table.
		Just 10 years ago, there were less than 5000 network routes in the entire Internet.
		That way, all the big ISP's customers (and their customers, and so on) are accessible via 1 network route on the Internet.
	www.ralphb.net /IPSubnet/cidr.html (619 words)

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