D. Wessels and K. Claffy, "Application of Internet cache protocol (ICP), version 2," Internet Engineering Task Force, Internet Draft:draft-wessels -icp-v2-appl-00. Work in Progress., May 1997.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....a certain document, which relaxes the inflexible reload option that always polls the origin server. When a document is requested through a caching hierarchy some additional delays are introduced: 1) Resolution delay, which is the time to check if the document is present in an ISP (ICP queries [26], hashing function [20] routing [ In order to keep this delay low a caching hierarchy should not have more than three levels [6] 2) TCP delay, which is due to the slow start phase of the different TCP connections between every cache level [17] The slow start is more relevant when the ....

....source and the receivers. Although a cache hierarchy mimics reliable multicast, it does not perform a perfect multicast as within an ISP the same version of the same document can be sent over a link multiple times. However, there are a number of proposals to have caches communicate via multicast [26] [16] Thus, CMP is an attractive scheme to deliver hot changing documents. However, multicast distribution of Web documents on the Internet is still in its infancy as a viable service; in fact, very few network providers offer it as a service [11] In particular, a continuous multicast ....

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D. Wessels and K. Claffy, "Application of Internet Cache Protocol (ICP), version 2", Internet Draft:draftwessels -icp-v2-appl-00. Work in Progress., Internet Engineering Task Force, May 1997.

....caches, institutional caches need other mechanisms to share the documents they contain. Some of these mechanisms are: ffl Institutional caches can query the other cooperating institutional caches for documents that resulted in local misses (this is usually done using the Inter Cache Protocol ICP [34]) However, using a query based approach may significantly increase the bandwidth consumption and the experienced latency by the client since a cache needs poll all cooperating caches and wait for the slowest one to answer. ffl Institutional caches can keep a digest [27] or summary [12] of the ....

.... caching architecture to handle highly popular information [3] In Europe many countries have also deployed caching hierarchies to reduce the number of requests that traverse the highly congested transoceanic links [3] 28] Distributed caching is used in several cache cooperating schemes [34] [27] 31] and several researchers have proposed to deploy a large scale distributed caching cooperation [30] 23] Moreover, distributed caching has recently become very relevant with the appearance of new applications that allow the distribution of different content (Web pages, images, music) ....

[Article contains additional citation context not shown here]

D. Wessels and K. Claffy, "Application of Internet Cache Protocol (ICP), version 2", Internet Draft:draft-wessels-icp-v2-appl-00. Work in Progress., Internet Engineering Task Force, May 1997.

....institutional caches need other mechanisms to share the doc 2 uments they contain. Some of these mechanisms are: ffl Institutional caches can query the other cooperating institutional caches for documents that resulted in local misses (this is usually done using the Inter Cache Protocol ICP [34]) However, using a query based approach may significantly increase the bandwidth consumption and the experienced latency by the client since a cache needs poll all cooperating caches and wait for the slowest one to answer. ffl Institutional caches can keep a digest [27] or summary [12] of the ....

.... caching architecture to handle highly popular information [3] In Europe many countries have also deployed caching hierarchies to reduce the number of requests that traverse the highly congested transoceanic links [3] 28] Distributed caching is used in several cache cooperating schemes [34] [27] 31] and several researchers have proposed to deploy a large scale distributed caching cooperation [30] 23] Moreover, distributed caching has recently become very relevant with the appearance of new applications that allow the distribution of different content (Web pages, images, music) ....

[Article contains additional citation context not shown here]

D. Wessels and K. Claffy, "Application of Internet Cache Protocol (ICP), version 2", Internet Draft:draft-wessels-icp-v2-appl-00. Work in Progress., Internet Engineering Task Force, May 1997.

....summarize our findings and conclude the paper. A. Related Work Hierarchical Web caching was first proposed in the Harvest project [6] to share the interests of a large community of clients. In the context of distributed caching, the Harvest group also designed the Internet Cache Protocol (ICP) [26], which supports discovery and retrieval of documents from neighboring caches as well as par 3 ent caches. Other approach to distributed caching is the Cache Array Routing Protocol (CARP) 24] which divides the URL space among an array of loosely coupled caches and lets each cache store only the ....

....their content, and keep local directories to facilitate finding documents in other caches. Concerning a hybrid scheme, ICP allows for cache cooperation at every level of a caching hierarchy. The document is fetched from the parent neighbor cache with a document copy that has the lowest RTT [26]. Rabinovich et al. 16] proposed to limit the cooperation between neighbor caches to avoid obtaining documents from distant or slower caches, which could have been retrieved directly from the origin server at a lower cost. II. THE MODEL A. Network Model As shown in Figure 1, the Internet ....

D. Wessels and K. Claffy, "Application of Internet Cache Protocol (ICP), version 2", Internet Draft:draft-wessels-icp-v2-appl-00. Work in Progress., Internet Engineering Task Force, May 1997.

....Inst9L Waseda Universit y Telecommunicat66 Advancement Organizat81 of Japan, Okinawa Research CentL1 Tokyo, 169 0051 Japan. prop osp [4] 14] Inthis paper, we focus on the following major conventionals hemes for comparisM with the prop osp method. The ICP (Internet cache protocol) s heme [4] [7]is a commonlyusm disnlyj;UR cache sSP er architecture. The well known cache sP9 er sj8 ware Squidusi ICP; in it, if the cachesj8 eris notpresS tly holding the objectas cache data, itsj87 querymesyjS; toits ssLUL cachesj; ers If one of themis holding the object, the queryingser er downloads that ....

....adisCUCj from each other in a wide area network. Next, we willdisjP9 robus hasusC and a double query method for overcoming theproblems ofsj9 er failure and addition. Finely, we willdisj79 pos7;7j applications ofthis method. 2. ICP and Hd3 Routing 2. 1 ICP (Internet Cache Protocol) The ICP [6] [7]is basP on pinging cachesj7 ers in to locate an object. Each client is configured to connect to a particularsrt er. Inthis paper, we call a configured cachesjR er a local cachesjP er. When a local cache sej er receives areques from a client, itfirs checks itsj7 to sj if it cansnjP;7 therequesC If ....

D. Wessels and K. Ka#y,"Application of internet cache protocol (ICP),version 2," RFC1287,Sept. 1997.

....a certain document, which relaxes the inflexible reload option that always polls the origin server. When a document is requested through a caching hierarchy some additional delays are introduced: 1) Resolution delay, which is the time to check if the document is present in an ISP (ICP queries [26], hashing function [20] routing [ In order to keep this delay low a caching hierarchy should not have more than three levels [6] 2) TCP delay, which is due to the slow start phase of the different TCP connections between every cache level [17] The slow start is more relevant when the ....

....source and the receivers. Although a cache hierarchy mimics reliable multicast, it does not perform a perfect multicast as within an ISP the same version of the same document can be sent over a link multiple times. However, there are a number of proposals to have caches communicate via multicast [26] [16] Thus, CMP is an attractive scheme to deliver hot changing documents. However, multicast distribution of Web documents on the Internet is still in its infancy as a viable service; in fact, very few network providers offer it as a service [11] In particular, a continuous multicast ....

[Article contains additional citation context not shown here]

D. Wessels and K. Claffy, "Application of Internet Cache Protocol (ICP), version 2", Internet Draft:draftwessels -icp-v2-appl-00. Work in Progress., Internet Engineering Task Force, May 1997.

.... In hierarchical caching, caches are usually placed at the access points between two different networks to reduce the cost of transmitting across a new network [5] One popular protocol which allows Web clients to coordinate and share a hierarchy of Web caches is the Internet Caching Protocol (ICP) [15]. However, the hierarchical topology and ICP have several drawbacks: First, the disk space utilization is relatively low due to mirroring effect only a fraction of the total storage capacity contains unique objects. Second, if the document is not hit in the cache, additional latency is added ....

....2. Satellite distribution. The satellite caching distribution works as follows. Whenever there is a miss at an ISP cache, the ISP cache obtains the document from the origin Web server via HTTP protocol. The ISP cache reports the missed URL (Universal Resource Location) to a master site via ICP [15]. The master site then obtains the document from the origin server and transmits the document into the satellite channel. As a result, all ISP caches receive the broadcasted document and can decide to keep it or not. Each ISP cache receives all the documents requested by any client connected to ....

D. Wessels and K. Claffy, "Application of Internet Cache Protocol (ICP), version 2", Internet Draft:draft-wessels-icp-v2-appl-00. Work in Progress., Internet Engineering Task Force, May 1997.

....research on how to make caches cooperate to increase the total effective client population, increase the hit ratios, and reduce the document access latency. Web caching cooperation was first proposed in the context of the Harvest project [10] that designed the Internet Cache Protocol (ICP) [31], which supports discovery and retrieval of documents from neighboring caches. Today, many caches have established hierarchies of caches that cooperate via ICP [3] Other approaches to make caches cooperate have been proposed recently, such as the Cache Array Routing Protocol (CARP) 29] the ....

D. Wessels and K. Claffy, "Application of Internet Cache Protocol (ICP), version 2", Internet Draft:draftwessels -icp-v2-appl-00. Work in Progress., Internet Engineering Task Force, May 1997.

....interested in the same document. ISPs cooperate and serve each others misses to increase the number of documents that are hit at close network levels. Web caching cooperation was first proposed in the context of the Harvest project [10] The Harvest group designed the Internet Cache Protocol (ICP) [30], which supports discovery and retrieval of documents from neighboring caches. Today, many caches have established hierarchies of caches that cooperate via ICP [3] Other approaches to make caches cooperate have been proposed recently, Cache Array Routing Protocol (CARP) 28] the central ....

D. Wessels and K. Claffy, "Application of Internet Cache Protocol (ICP), version 2", Internet Draft:draftwessels -icp-v2-appl-00. Work in Progress., Internet Engineering Task Force, May 1997.

....the degree of cooperation between caches at every level of a hybrid caching scheme. 1. 1 Related Work Hierarchical Web caching cooperation was first proposed in the Harvest project [6] In the context of distributed caching, the Harvest group also designed the Internet Cache Protocol (ICP) [22], which supports discovery and retrieval of documents from neighboring as well as parent caches. Other approaches to make caches cooperate in a distributed fashion, have been recently proposed. Cache Array Routing Protocol (CARP) 20] which divides the URL space among an array of loosely coupled ....

D. Wessels and K. Claffy, "Application of Internet Cache Protocol (ICP), version 2", Internet Draft:draft-wesselsicp -v2-appl-00. Work in Progress., Internet Engineering Task Force, May 1997.

....and the new copy; otherwise, the server returns the code 304 , which stands for document unmodified. When a document is requested through a caching hierarchy some additional delays are introduced: 1) Resolution delay, which is the time to check if the document is present in an ISP (ICP queries [27], hashing function [21] routing [25] In order to keep this delay low a caching hierarchy should not have more than three levels [7] 2) TCP delay, which is due to the slow start phase of the different TCP connections between every cache level [18] The slow start is more relevant when the ....

....source and the receivers. Although a cache hierarchy mimics reliable multicast, it does not perform a perfect multicast as within an ISP the same version of the same document can be sent over a link multiple times. However, there are a number of proposals to have caches communicate via multicast [27] [17] Thus, CMP is an attractive scheme to deliver hot changing documents. However, multicast distribution of Web documents on the Internet is still in its infancy as a viable service; in fact, very few network providers offer it as a service [12] In particular, a continuous multicast ....

D. Wessels and K. Claffy, "Application of Internet Cache Protocol (ICP), version 2", Internet Draft:draftwessels -icp-v2-appl-00. Work in Progress., Internet Engineering Task Force, May 1997.

....as there may be on a file system. However, going through a caching hierarchy to obtain a document has several additional delays that a multicast distribution has not: ffl Resolution delay: This delay accounts for the time to check if the document is kept by any cache at that level (ICP queries [26], hashing function [21] routing [24] ffl TCP delay: This delay is due to the slow start phase of the different TCP connections between every cache level [17] The slow start is more relevant when the completion time of the document is small. The effect of this delay gets very reduced when ....

....distribution uses bandwidth efficiently by sharing all common paths between the source and the receivers. In the current caching hierarchy, communication is generally done via unicast between the different cache levels (there have been a number of proposals to communicate caches via multicast [26] [15] A continuous multicast push for popular documents that change frequently seems to be the best way to deliver this kind of information. However, multicast distribution of Web documents on the Internet is still in its infancy as a viable service; in fact, very few network providers offer it ....

D. Wessels and K. Claffy, "Application of Internet Cache Protocol (ICP), version 2", Internet Draft:draft-wessels-icp-v2-appl-00. Work in Progress., Internet Engineering Task Force, May 1997.

....as there may be on a file system. However, going through a caching hierarchy to obtain a document has several additional delays that a multicast distribution has not: ffl Resolution delay: This delay accounts for the time to check if the document is kept by any cache at that level (ICP queries [26], hashing function [21] routing [24] ffl TCP delay: This delay is due to the slow start phase of the different TCP connections between every cache level [17] The slow start is more relevant when the completion time of the document is small. The effect of this delay gets very reduced when ....

....distribution uses bandwidth efficiently by sharing all common paths between the source and the receivers. In the current caching hierarchy, communication is generally done via unicast between the different cache levels (there have been a number of proposals to communicate caches via multicast [26] [15] A continuous multicast push for popular documents that change frequently seems to be the best way to deliver this kind of information. However, multicast distribution of Web documents on the Internet is still in its infancy as a viable service; in fact, very few network providers offer it ....

D. Wessels and K. Claffy, "Application of Internet Cache Protocol (ICP), version 2", Internet Draft:draft-wessels-icp-v2-appl-00. Work in Progress., Internet Engineering Task Force, May 1997.

....of cooperating caches. In Section 7 we summarize our findings and conclude the paper. 1. 1 Related Work Hierarchical Web caching cooperation was first proposed in the Harvest project [6] In the context of distributed caching, the Harvest group also designed the Internet Cache Protocol (ICP) [20], which supports discovery and retrieval of documents from neighboring caches as well as parent caches. Other approach to distributed caching is the Cache Array Routing Protocol (CARP) 19] which divides the URL space among an array of loosely coupled caches and lets each cache store only the ....

....their content, and keep local directories to facilitate finding documents in other caches. Concerning a hybrid scheme, ICP allows for cache cooperation at every level of a caching hierarchy. The document is fetched from the parent neighbor cache with a document copy that has the lowest RTT [20]. Rabinovich et al. 10] proposed to limit the cooperation between neighbor caches to avoid obtaining documents from distant or slower caches, which could have been retrieved directly from the origin server at a lower cost. In this paper we analyze the advantages and inconvenient of both, ....

D. Wessels and K. Claffy, "Application of Internet Cache Protocol (ICP), version 2", Internet Draft:draft-wessels-icp-v2-appl-00. Work in Progress., Internet Engineering Task Force, May 1997.

....distribution uses bandwidth efficiently by sharing all common paths between the source and the receivers. In the current caching hierarchy, communication is generally done via unicast between the different cache levels (there have been a number of proposals to communicate caches via multicast [49] [32] Therefore a continuous multicast push for popular documents that change frequently seems to be the best way to deliver this kind of information on the Internet. However, multicast distribution of Web documents on the Internet is still in its infancy as a viable service; in fact, very few ....

D. Wessels and K. Claffy, "Application of Internet Cache Protocol (ICP), version 2", Internet Draft:draft-wessels-icp-v2-appl-00. Work in Progress., Internet Engineering Task Force, May 1997.

....consists of a fixed, 20 octet header plus a variable sized payload, the latter of which typically contains a URL. Figure 2 shows the ICP message format; all fields are represented in network byte order. 3 3 As of this writing the most current description of ICP is in Wessels Internet Drafts [47, 48]. ffl OPCODE: indicates the type of message. Some common opcodes are icp query, icp miss, and icp hit. ffl VERSION: ICP protocol version, for maintaining backward compatibility. ffl PACKET LENGTH: total size of the ICP message. ffl REQUEST NUMBER: an opaque integer identifier to match queries ....

....hit obj feature does pose a potential problem if the source IP address can be spoofed (another reason to avoid using icp hit obj) Nonetheless, a cache should verify the address and port number of every ICP message it receives, and only accept ICP replies from known peers. The ICP Internet Draft [48] has additional details on security concerns. 6.4.3 ICP Scales Poorly ICP has poor scaling characteristics. It is not really practical to send more than about five ICP queries for each HTTP request, if only because it increases the chance of losing at least one ICP reply and therefore frequently ....

D. Wessels and K. Claffy, "Application of internet cache protocol (ICP), version 2," draftwessels -icp-v2-appl-02.txt, July 1997. http://ds.internic.net/internet-drafts/draftwessels -icp-v2-appl-03.txt.

....has a given document, sibling relationships would not even be possible. ICP provides this functionality. In this article we assume the reader is already familiar with HTTP 1.0[2] and at least aware of HTTP 1. 1[3] For additional information on ICP, please see our Internet Drafts (soon to be RFCs)[4, 5] and other work[6] 2 Squid 2.1 History Squid was developed as a follow on to one component of the Harvest project[7] the latter effort originally funded in 1994 by the U.S. Advanced Projects Research Agency (ARPA) Harvest focused on developing tools for effective use of Internet ....

D. Wessels and K. Claffy, "Application of internet cache protocol (ICP), version 2," draft-wesselsicp -v2-appl-02.txt, July 1997. http://ds.internic.net/internet-drafts/draft-wessels-icp-v2appl -03.txt.

....the design of Web cache hierarchies is efficiently locating objects held in neighbor caches. When a cache needs to forward a request, how does it know whether to use a sibling, a parent, or perhaps the origin server directly Many caches in operation today utilize the Internet Cache Protocol (ICP)[1, 2] for this purpose. Although ICP works reasonably well, it can add significant delays to cache misses. When neighbor caches are located close to each other (e.g. within an organizational LAN) ICP delays are usually not significant. In a wide area environment, however, ICP becomes troublesome. This ....

....memory, but ICP does not. 2 The Problem Connecting a Web cache into a hierarchy or mesh offers additional benefits from Web caching technology. To determine which member of a cache group (if any) a cache miss should be forwarded to, many caches use the lightweight Internet Cache Protocol (ICP)[1, 2]. ICP messages are transmitted via UDP. A message consists of a 20 byte fixed format header plus a URL. A cache sends an icp query message to one or more neighbor caches. The neighbors reply with icp hit or icp miss messages to indicate the presence or absence of the named object in their cache. ....

D. Wessels and K. Claffy, "Application of internet cache protocol (ICP), version 2," Network Working Group RFC 2186, September 1997. http://ds.internic.net/rfc/rfc2187.txt.

No context found.

D. Wessels and K. Claffy, "Application of Internet cache protocol (ICP), version 2," Internet Engineering Task Force, Internet Draft:draft-wessels -icp-v2-appl-00. Work in Progress., May 1997.

No context found.

D. Wessels and K. Claffy, "Application of Internet Cache Protocol (ICP), version 2", Internet Draft:draftwessels -icp-v2-appl-00. Work in Progress., Internet Engineering Task Force, May 1997.

No context found.

Wessels, D. and K. Claffy, "Application of Internet Cache Protocol (ICP), Version 2", RFC 2187, September 1997.

No context found.

D. Wessels, and K. Claffy. "Applications of Internet Cache Protocol (ICP), version 2," RFC-2186, September 1997.

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