H. Balakrishnan, S. Seshan, E. Amir, R. H. Katz. Improving TCP/IP Performance over Wireless Networks. 1st ACM Conference on Mobile Computing and Networking, November 1995.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....At this point, the client TCP completes the migration by transparently switching the client process to the local endpoint of the new TCP connection and continues data transfer on it. 4 Related Work TCP IP connection hand o protocols have been used either for mobility extensions to TCP IP [4, 5, 6] or for request distribution in clusters [3] The mobile TCP approaches do not consider the task of migrating the connection endpoints between physically distinct machines. They either rely on directly using the full connection state maintained at the physical endpoints [4, 5] or on restarting a ....

....to TCP IP [4, 5, 6] or for request distribution in clusters [3] The mobile TCP approaches do not consider the task of migrating the connection endpoints between physically distinct machines. They either rely on directly using the full connection state maintained at the physical endpoints [4, 5], or on restarting a previously established connection after a change of the IP address by reusing the state of the old connection after proper authentication [6] 3] proposes TCP connection hand o in clustered HTTP servers for distributing incoming requests from a front end machine to the ....

H. Balakrishnan, S. Seshan, E. Amir, R. H. Katz. Improving TCP/IP Performance over Wireless Networks. 1st ACM Conference on Mobile Computing and Networking, November 1995.

....(TCP tra#c constitutes 80 of all the wide area network tra#c [4] It is important that existing applications continue to work in presence of wireless links without severe degradation in their performance. The problem has been studied by several researchers, and many solutions have been proposed [1, 2, 8, 11]. Nanda et al. 8] have suggested to solve the problem by introducing reliability at the link layer for wireless link using finite number of retransmissions. This approach does not completely shield the source transport layer from all losses on the wireless link, resulting in degraded performance. ....

....significant amount of state for every TCP connection passing through it. Lastly, in Bakre s approach [1] since TCP is not tuned for wireless links, TCP sender of the wireless link often times out causing the original sender to stall. This results in performance problems. Balakrishnan et al. [2] have suggested adding a module called snoop agent to the routing code at the base station. This agent monitors packets flowing on a TCP connection and does intelligent processing, utilizing the knowledge of TCP. It maintains a cache of un acknowledged TCP packets on a per connection basis and ....

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H. Balakrishnan, S. Seshan, E. Amir, and R.H. Katz. Improving TCP/IP performance over wireless networks. In Proc. 1st ACM International Conference on Mobile Computing and Networking (Mobicom), November 1995.

....of allocating time slots on the wireless link to different data streams, based on the high level protocol requirements, and the actual physical channel constraints. 2. 1 IP over Fading Channels The problem of transmitting TCP IP flows over wireless links has been addressed in several publications [1, 11, 12]. TCP was designed for high bandwidth, wired networks, where retransmission timeouts most probably are a cause of traffic congestion at some node along the path, not due to erroneous reception because of bad channel conditions. The action taken by TCP at the source, apart from retransmitting the ....

....to counteract the effects of a lossy wireless link. In a split connection, a proxy server at the basestation handles the TCP connection with the source host at one end, and the destination host at the other. In the latter case, end to end TCP, a snoop agent could be used to improve TCP performance [1]. The snoop agent, hosted by the base station, would have a shorter retransmission timeout, expecting ACKs to come quicker from the mobile host, and thus handling some of the retransmissions that would have otherwise been done by the original TCP source. The snoop agent also selectively passes ....

H. Balakrishnan, S. Seshan, E. Amir, and R. H. Katz. Improving TCP/IP Performance over Wireless Networks. In Proc. MOBICOM, pages 2--11, Berkeley, CA, 1995.

....for the I TCP connection over wireless, but we believe that using a smaller retransmission timeout and fast retransmissions possibly coupled with selective acknowledgments should result in a much better performance by I TCP. Some such special measures were incorporated in the snoop layer protocol [15] for the wireless link resulting in large performance improvement over TCP. 4.6 Alternatives to Indirect Transport Protocols We list some of the approaches that other researchers have taken to solve mobility and wireless related problems that affect transport layer performance in a mobile ....

....need to handoff versus sub optimal quality of service effected by placing the intermediaries away from the wireless link. 3. Mechanisms for reducing handoff latency need to be explored. One such method uses multicasting to pre notify other MSRs about the state information about TCP snoop layer [15]. This however results in extra traffic and locking of additional resources at MSRs because each potential MSR that a mobile can visit next needs to be ready with the state information for smooth handoffs. Another issue is the amount of state carried by the mobile itself which may assist in ....

H. Balakrishnan, S. Seshan, E. Amir, and R.H. Katz. Improving TCP/IP performance over wireless networks. In Proc. of the 1st ACM Conf. on Mobile Computing and Networking (Mobicom-95), pages 2--11, November 1995.

.... disconnected operation via diskcaching [SK92] SNKP94] HHRB92] For improving application performance over wireless links, an M RPC system has been proposed [BB95a] Enhancements have been suggested to improve TCP performance over wireless links : split connection approaches [BB95b] YB94] BSAK95] and the fast retransmission approach [CI94] Link level retransmissions have also been proposed to improve performance over wireless links [DCY93] BBKT96] PAL 95] For reasons discussed shortly, most of these results are not directly applicable to improving NFS performance. Our research ....

....Prefetching and disk caching decrease the time spent by the user waiting for file transfers, but that by itself does not solve the problem of poor throughput and wireless link utilization. We discuss the use of disk caching in Section 5. In the TCP split connection approaches [BB95b] YB94] BSAK95] the base station 1 buffers packets being sent to the mobile hosts in its vicinity. The base station retransmits any lost packets to prevent end to end retransmission. The M RPC approach [BB95a] is a variation of the TCP split connection approach. It seeks to improve performance by separating ....

H. Balakrishnan, S. Seshan, E. Amir, and R.H. Katz. Improving TCP/IP Performance over Wireless Networks. In First ACM International Conference on Mobile Computing and Networking, November 1995.

.... reliable link layer mechanism conspire to confound the TCP congestion control mechanisms [BPK97] While many of these problems have previously been studied and understood, most solutions assume a basestation paradigm, where agents are inserted at the interface between the wired and wireless links [BKVP96, BSAK95]. In a commercial CDPD environment, however, users do not have access to the Mobile Data Base Stations (MDBS) and therefore cannot completely control the buffering, queuing, and retransmission mechanisms being used. Inverse multiplexing restores the basestation view, as one can consider the ....

....of a multiplexer failure. By terminating the connection at both ends, attention can be focused exclusively on the WWAN portion of the overall path, perhaps utilizing novel transport protocols specially designed or tuned for WWANs [AG98, DMT96, JB88] Alternatively, mechanisms such as Snoop agents [BSAK95] could be used if a transparent solution was desired in some particular environment. Rather than cloud our results with additional factors by considering various proposals for transport protocols, we instead use the performance of standard TCP as a benchmark for our multi link implementation. ....

H. Balakrishnan, S. Seshan, E. Amir, and R. Katz. Improving TCP/IP Performance over Wireless Networks. In Proceedings of the 1 st ACM International Conference on Mobile Computing and Networking (MOBICOM). November 1995.

....within the application design is given. 2 Note, the release date of this communication is 1996. However, it was not permitted to be released to the general public until 1997 (See attached note to [FI96] Network variation awareness has been addressed heavily from the system level. Snoop TCP [BSAK95] and indirect TCP [BB95] propose transport layer protocol improvement for wireless networks. Fox et al. FGBA96] showed how proxy support can be used in wireless networks. In our work, we demonstrate how to improve performance from the application level. Other approaches, such as the Rover ....

H. Balakrishnan, S. Seshan, E. Amir, and R. Katz. Improving tcp/ip performance over wireless networks. In Mobile Computing and Networking, Hong Kong, Nov 1995.

....in the performance of TCP that was originally developed for wired networks. For example, TCP misinterprets packet loss over a wireless link as a sign of network congestion, causing poor throughput. The problem has been studied by several researchers, and many solutions have been proposed [1, 2, 6, 7]. Nanda et al. 6] have suggested introducing reliability at the link layer for wireless link using finite number of retransmissions. This approach does not completely shield the source transport layer from all losses on the wireless link. Also, studies [4] have shown that linklayer ....

....However, this approach does not preserve the semantics of TCP. Also, every packet incurs the overhead of going through the TCP protocol processing twice at the base station. Further, it requires the base station to maintain state for every TCP connection passing through it. Balakrishnan et al. [2] have suggested adding a module called snoop agent to the routing code at the base station. This agent monitors packets flowing on a TCP connection. It maintains a cache of unacknowledged TCP packets on a per connection basis and performs local retransmission when it detects a packet loss. This ....

H. Balakrishnan, S. Seshan, E. Amir, and R. H. Katz. Improving TCP/IP performance over wireless networks. In Proc. 1st ACM Int'l Conf. on Mobile Comp. and Networking (Mobicom), November 1995.

....hazards. First, from an architectural standpoint, a split TCP connection that is not explicitly associated with a proxy or a cache breaks the end to end semantics of the transport layer. Although approaches for TCP improvement over local area wireless links, such as Berkeley s snoop protocol [10] and mobile TCP [21] can preserve end to end semantics, it is more difficult to do so in the satellite environment because combating the fairness problem relies on early acknowledgment of data. However, steps can be taken to ensure that the connection does not close normally unless all data has ....

H. Balakrishnan, V. Padmanabhan, E. Amir, and R. Katz. Improving TCP/IP Performance over Wireless Networks. Proceedings of First ACM/IEEE MobiCom Conference, November 1995.

....the second leg of the connection, a di erent protocol that is better suited to the characteristics of wireless link can be used. The limitations of I TCP are, breakage of TCP s end to end semantic, relinkage of applications and considerable overheads due to the additional protocol stacks at the BS [94]. Further, I TCP does not guarantee smooth hando since packets maybe lost while states are being transferred from the previous BS. A reliable transfer of states from BSs that are robust to varying migration scenario is presented in [95] The split connection approach was further improved by Wang ....

....The states are restored once interference is over. Secondly, an aggressive retransmission which enables fast recovery after retransmission is proposed. Finally, an algorithm is used at the receiver to overcome the inadequate recovery rate at receiver s side due to interference. The snoop protocol [94] involves the installation of an agent at the BS. This agent is transparent to both communicating ends. The main function of this agent is to keep track of TCP packets transmitted to the MH. The agent caches unacknowledged data thereby allowing local recovery if a given packet is lost at the ....

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H. Balakrishnan, S. Seshan, E. Amir, and R. H. Katz, \Improving TCP/IP performance over wireless networks," in Proceedings of the rst Annual International Conference on Mobile Computing and Networking (Mobicom '95), pp. 2-11, Nov. 1995.

....loss. An advanced version of SACKs is FACK [14] which uses the additional information provided by the SACK option to keep an explicit measurement of the amount of segment outstanding in the network, and then uses this information to improve congestion control. Indirect TCP(I TCP) 3] and Snoop [5] Protocols use split connections. The key idea behind these protocols is to split one TCP connection into multiple pieces in wired and wireless links. Congestion control at the wireless link is performed differently from the control at the wired link. Thus, these protocols aim to improve the ....

H. Balakrishnan, S. Seshan, and R.H. Katz. Improving TCP/IP Performance over Wireless Networks. In Proceedings of ACM MOBICOM '95, Nov. 1995.

....within the data link layer to reduce the error rate experienced by the transport layer. However, link level retransmissions and TCP s retransmissions possibly interfere and thus, cause redundant retransmissions. An approach that realizes retransmissions within the network layer is presented in [3]. To avoid redundant retransmissions, the network layer snoops TCP PDUs encapsulated within IP PDUs. Furthermore, information about TCP s connection state is utilized within the network layer of the node connecting the wireless and the wirelined subpath. However, snooping and processing transport ....

H. Balakrishnan, S. Seshan, E. Amir, and R. H. Katz. Improving TCP/IP Performance over Wireless Networks. Proceedings of Mobicom '95, Berkeley, California, November 1995.

....on two basic design principles for achieving reliance against system failures: soft state, and timeouts. The concept of soft state has been used in a number of systems to achieve better reliability. For example, many networking systems for routing protocols [39, 19] and performance optimization [9] rely on soft state, periodic update mechanisms to keep their tables up to date. By explicitly designing our system to rely entirely on soft state, we have managed to simplify our crash recovery process. No explicit crash recovery is required recovery is built into the normal functioning of the ....

....The only way to kill both ghosts was to kill them simultaneously or to deliberately crash the system. 23] A number of other systems have used the notion of soft state to achieve better performance and robustness. Networking systems for routing protocols [39, 19] and performance optimization [9] rely on soft state to update their tables; this allows them to continue operating in the event of partial failures and ensures that no special recovery protocols are needed to regenerate state that might have been lost in a crash. Various soft state systems such as Bayou [21] have explicitly ....

Balakrishnan, H., Seshan, S., Amir, E., and Katz, R. Improving TCP/IP Performance Over Wireless Networks. In Proceedings of the first ACM Conference on Mobile Computing and Networking (Berkeley, CA, Nov. 1995).

....we have observed in our experiments with the CDPD network. In recent years, there have been several proposals to optimize TCP for wireless networks. These proposals typically have had three flavors: a) improving reliability at the link layer [6] b) providing TCP aware smarts in the base station[4], and (c) splitting the TCP connection into two parts [3, 13] one in the backbone network and one over the wireless link running a specialized protocol [13] Most of these solutions focus almost exclusively on making the loss characteristics of the wireless link transparent to the sender, while ....

....To this end, we present the Wireless Transmission Control Protocol (WTCP) which enunciates the following three key principles: 1. WTCP uses purely end to end mechanisms, thereby eliminating the need for transport level support from the network infrastructure, in contrast to related work [6, 4, 3, 13]. We choose end to end mechanisms for three reasons. First, we believe that end to end mech anisms are necessary to effectively address the problems of WWAN environments. Second, the connection end points in most of the current WWAN deployment scenarios are a mobile host and a dedicated proxy ....

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H. Balakrishnan, S. Seshan, E. Amir, and R. Katz. Improving TCP/IP performance over wireless networks. In ACM MOBICOM, November 1995.

....the relevant parameters and initiates object migration if necessary. Object migration is achieved by a mobile code technology based on Java (Objectspace Voyager [24] A low level proxy supports the communication between client and high level proxy. One example of such a low level proxy is SNOOP [3]. The low level proxy operates at the data, network, and or transport layers. Protocols at these layers are typically provided as part of the operating system protocol stack, so for maximal efficiency we expect the lowlevel proxy to become part of the operating system. The low level proxy supports ....

H. Balakrishnan, S. Seshan, E. Amir, and R. H. Katz, Improving TCP/IP Performance over Wireless Networks, Proceedings of the First Annual International Conference on Mobile Computing and Communications, Berkeley, USA, November 1995, pages 211.

....we have observed in our experiments with the CDPD network. In recent years, there have been several proposals to optimize TCP for wireless networks. These proposals typically have had three avors: a) improving reliability at the link layer [3] b) providing TCP aware smarts in the base station[4], and (c) splitting the TCP connection into two parts [5,6] one in the backbone net 2 work and one over the wireless link running a specialized protocol [6] Most of these solutions focus almost exclusively on making the loss characteristics of the wireless link transparent to the sender, ....

....and the majority ( 75 ) of the end to end latency is incurred 3 in the CDPD part of the network between the mobile switching station and the mobile host. We will revisit the impact of the latter point when we discuss wireless transport protocols that rely on TCP aware smarts at the base station [4]. WWAN wireless networks in general, and CDPD networks in particular, typically exhibit the following six characteristics. 1. Non congestion related packet loss: Even though CDPD adds 134 bits of Reed Solomon error correcting code to every 278 bit block of data, we have measured non congestion ....

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H. Balakrishnan, S. Seshan, E. Amir, and R. Katz, \Improving TCP/IP performance over wireless networks," Proc. of ACM MOBICOM, 1995.

....the intermediary can act not only as a filter, but also as an agent; i.e. as a permanent representative for a mobile host that might not always be powered up or connected to the Internet. Such an indirect approach has been advocated before for dealing with resource constrained mobile systems [3, 6, 8, 28, 41, 52, 64, 82]. In general, the intermediary implements an extra level of indirection, permitting run time adjustment of design time decisions about the nature and amount of client server traffic. Some of these advantages can be achieved without the use of proxies. However, without a proxy in most cases both ....

....control algorithm used by TCP is not valid in a weakly connected environment. Some solutions [8, 82] improve TCP performance at the cost of breaking TCP s end toend semantics, while other s [19] attempt to improve the protocol itself. An alternative solution investigated by Balakrishnan et al. [2, 3] proposes the use of an intermediary that snoops TCP conversations, but does not break the end to end semantics. The main purpose of the intermediary is to cache packets headed towards the Mobile Host and to perform local retransmissions when packet loss between the intermediary and Mobile Host ....

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E. Amir, H. Balakrishnan, S. Seshan, and R. H. Katz. Improving TCP/IP Performance over Wireless Networks. In Proc. First Annual International Conference on Mobile Computing and Networking, pages 2--11. ACM, November 1995.

.... machines of the agents (the server machine and the user machine) one advantage of using agent programming is that the network usage for the messages transferred can largely be reduced [29] Owing to the tremendous growth of the size of Internet and the latest development of mobile computing [1] [2] [23] 24] 27] a low usage network management technology, like mobile agent based network management, will be increasingly demanded. In recent years, many intelligence mobile agent based network management techniques have been proposed and implemented [3] 9] 25] 31] In fault diagnosis [9] ....

H. Balakrishnan, S. Seshan, E. Amir and R. Katz, Improving TCP/IP performance over wireless networks, Proc. 1st ACM International Conf. on Mobile Computing and Networking (Mobicom), Nov., 1995.

....both the drivers timeout and finally report a failure of the RPC call. However, the unmodified driver actually sends the packets over the link resulting in more energy consumption. 4. Related work Link layer retransmissions [8, 9] or transmission at higher layers only for the wireless link [4] have been suggested to handle lossy wireless links. Most of these efforts suggest aggressive transmission policies to make up for the lost packets. State dependent packet scheduling for handling bursty errors from MSR to MH has been suggested in[5] Our approach is a cautious approach for ....

H. Balakrishnan et al. Improving TCP/IP performance over wireless networks. In Proceedings of the 1st MobiCom Conference, Berkeley, CA, November 1995.

.... nomadic agents [2] and gateways are nodes that support mobility. They are located at strategic points that bridge networks with vastly different bandwidth and reliability characteristics, such as the junctions between wired and wireless networks. Application neutral work on TCP snooping [3] improves the performance of TCP connections by retaining per connection state information at wireless base stations. Application specific services performed at gateways include file caching and the transcoding of images [4] The InfoPad [5] takes the process even further, by instantiating ....

Balakrishnan, H., et al. Improving TCP/IP Performance over Wireless Networks . in Int. Conf. on Mobile Computing and Networking. 1995. Berkeley, CA.

....endto end communication in ad hoc networks, similar to that provided by TCP over the Internet. The end to end communication problem has been studied in the context of cellular wireless networks and a number of modifications and extensions to regular TCP for such networks have been proposed [1, 2, 3, 4, 18, 19]. It is desirable to use TCP directly even in ad hoc networks in order to provide seamless portability to applications like file transfer, email and WWW browsers written using standard TCP libraries. Hence, it is of interest to c e f h j a i k S1 S2 D2 D1 S1 S2 D2 D2 D1 c g i i e d f d b b a ....

Balakrishnan, H., Seshan, S., Amir, E., and Katz, R., H. Improving TCP/IP Performance over Wireless Networks. In Proceedings 1st ACM Conf. on Mobile Computing and Networking, November 1995.

....can not be directly used since most NFS implementations (using UDP) are incompatible with NFS over TCP. Although NFS uses RPC, the M RPC approach would require modifications to the RPC and NFS code on both the client and the server and endanger the consistency of NFS files. In the snoop approach [BSAK95] an agent at the base station monitors all TCP packets and caches unacknowledged segments. For the cached packets, the snoop agent suppresses any duplicate acks, which indicate packet loss, and retransmits the lost packets. This approach preserves TCP semantics, while improving performance, but ....

....state with the bad state and allow time in the bad state to be arbitrarily small. A temporal model for the error behavior of the wireless channel is desired. The quality of the channel (good or bad) in such a model depends only on the current time instant. This differs from the model used in [BSAK95] which non stochastically corrupts a small percentage of the bits in transit over the wireless channel. We implement a temporal model by using a distribution for the periods spent in the good and bad states. We perform experiments with various distributions (including uniform and deterministic) ....

H. Balakrishnan, S. Seshan, E. Amir, and R.H. Katz. Improving TCP/IP Performance over Wireless Networks. In First ACM International Conference on Mobile Computing and Networking, November 1995. An extended version appears in ACM/Baltzer Journal on Wireless Networks, December 1995.

.... nomadic agents and gateways [4] are nodes that support mobility. They are located at strategic points that bridge networks with vastly different bandwidth and reliability characteristics, such as the junctions between wired and wireless networks. Application neutral work on TCP snooping [5] improves the performance of TCP connections by retaining perconnection state information at wireless base stations. Application specific services performed at gateways include file caching and the transcoding of images [6] The InfoPad [7] takes the process even further, by instantiating ....

Balakrishnan, H., et al. Improving TCP/IP Performance over Wireless Networks. in Int. Conf. on Mobile Computing and Networking. 1995. Berkeley, CA.

....cost and handoff delay with a slight increase in packet tunneling. Compared with the related work, the extension of Mobile IP with routing agents is orthogonal to techniques for route optimization [8, 10, 13, 15] fast intra subnet handoff [5] and improving TCP performance in wireless networks [3, 4, 9]. In fact it can be combined with these techniques for a better overall support for mobility. Although the extension of Mobile IP with routing agents can be viewed as a dynamic two level hierarchical architecture, it is different from other hierarchical schemes such as [7, 12] Unlike redirection ....

H. Balakrishnan, S. Seshan, E. Amir, and R.H. Katz. Improving TCP/IP performance over wireless networks. In ACM International Conference on Mobile Computing and Networking (Mobicom), November 1995.

....wireless links, it has been necessary to implement new wireless aware protocols. Because wireless links are both lossy and exhibit high latency, congestion based error correction protocols such as TCP are not appropriate for transmitting real time data from remote instruments to database nodes [1, 16]. However, since reliable transport must still be guaranteed to insure that all data eventually migrates from remote instrument logs into a stream log, some form of retransmission protocol is necessary. REINAS has adopted a simple User Datagram Protocol (UDP) based retransmission scheme utilizing ....

H. Balakrishnan, S. Seshan, E. Amir, and R. Katz. Improving TCP/IP performance over wireless networks. In Proceedings of the First ACM International Conference on Mobile Computing and Networking, San Jose, CA, November 1995.

....home office. Transport Gateways Transport gateways are nodes located at strategic points that bridge networks with vastly different bandwidth and reliability characteristics, e.g. at the junctions between wired and wireless networks. To support mobile access to wired networks, TCP snooping [4] retains per connection state information at wireless base stations. Application Services Application specific gateways support services such as the transcoding of images [5] among video conference users with differing bandwidth constraints. Similarly, InfoPad [6] instantiates user specific pad ....

Balakrishnan, H., et al. Improving TCP/IP Performance over Wireless Networks. in Intl. Conf. on Mobile Computing and Networking. 1995. Berkeley, CA.

....bandwidth, e.g. at wireless base stations. Services performed at these gateways include file caching and image transcoding [4] The InfoPad [5] takes this process further, instantiating user specific pad servers at intermediate nodes. Finally, researchers have investigated TCP snooping [6], in which per connection state information is retained at wireless base stations. 3. Active Technologies One of the reasons it will be possible to build and secure active networks is the availability of active technologies mechanisms that allow users to inject customized programs into shared ....

Balakrishnan, H., et al. Improving TCP/IP Performance over Wireless Networks. in Int. Conf. on Mobile Computing and Networking. 1995. Berkeley, CA.

....Our Charon prototype client for the Sony MagicLink [13] a then popular PDA, had a client footprint of only 45KB, including stack and heap usage. 5 Related Work At the network level, various approaches have been used to shield clients from the effects of poor (especially wireless) networks [17, 4]. At the application level, data transformation by proxy interposition has become particularly popular for HTTP, whose proxy mechanism was originally intended for users behind security firewalls. The mechanism has been harnessed for anonymization [7] Kanji transcoding [36, 40] ....

H. Balakrishnan, S. Seshan, E. Amir, and R. Katz. Improving tcp/ip performance over wireless networks. In Proc. of the 1st ACM Conference on Mobile Computing and Networking (MOBICOM 95), Berkeley, CA, November 1995.

....over the wireless network. This enables each part of the connection to be treated in a way that is well suited to the underlying communication media. In wireless LAN environment, similar approaches have successfully been used to improve the performance of TCP based communication (See [BB95, YB94, BSAK95] However, our approach is more general and allows improvements at the higher levels of communication, because it also supports application level mediators that are transparent to clients and servers. We also take into account the speci c characteristics of the low bandwidth wireless links by ....

H. Balakrishnan, S. Seshan, E. Amir, and R. Katz. Improving TCP/IP Performance over Wireless Networks. In Proc. of the First ACM International Conf. on Mobile Computing and Networking (MobiCom '95), Berkeley, California, USA, November 1995.

....product. A natural solution to the above problem is to hide the random loss in the wireless links from the TCP connection. Examples of some recently proposed solutions along these lines include a link layer retransmission of lost packets in the wireless link [2] and a TCP aware snoop protocol [1]. Both of these approaches are appropriate for situations where random loss occurs in the last hop of an Internet connection and it is difficult to evaluate the performance of such schemes in networks with multiple wireless hops. An alternative approach that addresses this problem effectively for ....

....in Section 2.2.1 and study the fairness of the congestion avoidance schemes in these cases. ffl So far, we have assumed that the output rate is fed back to the source which then increases or decreases its rate. Now, let s assume that the wireless link losses are isolated from the sources as in [2, 1] and instead of the output rate, the rate received at the switch is available to the user. Then, all losses perceived by the user are due to congestion in the network. This is similar to the problem studied in [3] Theorem 2.2 then holds in this case with p 1 = p 2 = 0, j 1 = j 2 = 1 and ....

H. Balakrishnan, S. Seshan, E. Amir, and R.H. Katz. Improving TCP/IP performance over wireless networks. In ACM Conference on Mobile Computing and Networking, 1995.

....bandwidth. There are other mobility induced variations that affect multimedia applications. Wireless networks have different characteristics associated with them, such as high bit 6 See http: www.ricochet.com for more information. error rates. Rutgers I TCP [3] and Berkeley s snoop protocol [4] use a specialized retransmission mechanism to avoid the performance problems that occur when TCP inappropriately invokes congestion control mechanisms in response to packet lost to bit errors. Systems that are highly mobile will require more advanced handoff schemes to reduce the disruption of ....

Balakrishnan, H., Seshan, S., Amir, E., and Katz, R. H. Improving TCP/IP Performance over Wireless Networks. In Proceedings of the First Annual International Conference on Mobile Computing and Networking (Berkeley, California, November 1995), pp. 2--11.

....on lossy wireless links. To alleviate these problems, various strategies have been used. Loss of throughput during cell handoff has been reduced by taking advantage of features in modern TCP implementations to restart TCP s retransmission timer [5] and multicasting packets to adjacent cells [3]. Bandwidth over lossy wireless networks has been improved by the use of a snoop protocol [3] where a local agent retransmits packets over the wireless connection. File systems can also make assumptions about the characteristics of the underlying network. For example, you can move a NFS client ....

.... Loss of throughput during cell handoff has been reduced by taking advantage of features in modern TCP implementations to restart TCP s retransmission timer [5] and multicasting packets to adjacent cells [3] Bandwidth over lossy wireless networks has been improved by the use of a snoop protocol [3] where a local agent retransmits packets over the wireless connection. File systems can also make assumptions about the characteristics of the underlying network. For example, you can move a NFS client away from its home network. Using Mobile IP, you can connect it to a foreign network and tunnel ....

Balakrishnan, H., Seshan, S., Amir, E., and Katz, R. H. Improving TCP/IP Performance over Wireless Networks. In Proceedings of the First Annual International Conference on Mobile Computing and Networking (Berkeley, California, November 1995), pp. 2--11.

....layer reliability guarantees. Other changes to TCP IP are that, when a connection migrates during cell handoffs, the slow start timer is reset so that the new MSR has time to establish a connection before other packets are sent. Other versions of modified TCP for mobile computing are described in [BSAK95, ABSK95, BKPV95] When the mobile hosts moves in Dataman, the mobile host requests that the new MSR ask the previous MSR to migrate its I TCP connection. The migration includes the TCP IP connection, sockets, protocol numbers, and any buffers to be received or sent. 2.3.6 Crosspoint Crosspoint ....

H. Balakrishnan, S. Seshan, E. Amir, and R. H. Katz. Improving TCP/IP performance over wireless networks. In Proceedings of the 1st ACM Conference on Mobile Computing and Networking, November 1995.

....been defined and the mobile issues discuss ed, the interaction between the MH and the network during a query will be shown. First, a detailed trace of a query will be presented followed by some examples. The MH will initiate the connection with the network. Using the TCP IP method discussed in [3] a wireless connection will be established between the MH and an MSR when the MH responds to an MSR s beacon with a GREETING packet. Once the network connection has been established, the CP must validate the MH s service authorization. When handshaking at all levels has been successfully ....

H. Balakrishnan, S. Seshan, E. Amir, and R. Katz. Improving TCP/IP Performance over Wireless Networks. In Proceedings of the 1st ACM Conference on Mobile Computing and Networking, 1995.

....load at the base station. File systems have high consistency requirements and would be vulnerable under some of the split connection approaches. Although NFS uses RPC, the M RPC approach would require modifications to the RPC and NFS code on both the client and the server. In the snoop approach [BSAK95] an agent at the base station monitors all TCP packets and caches unacknowledged segments. For the cached packets, the snoop agent suppresses 1 A base station is a bridge between the wired and the wireless segments of a network. any duplicate acknowledgments, which indicate packet loss, and ....

.... bad state to be arbitrarily small. A temporal model for the error behavior of the wireless channel is desired to capture the temporal nature of burst errors. The quality of the channel (good or bad) in such a model depends only on the current time instant. This differs from the model used in [BSAK95] which non stochastically corrupts a small percentage of the bits in transit over the wireless channel. We implement a temporal model by using a distribution for the periods spent in the good and bad states. We perform experiments with various distributions (including uniform and deterministic) ....

H. Balakrishnan, S. Seshan, E. Amir, and R.H. Katz. Improving TCP/IP Performance over Wireless Networks. In First ACM International Conference on Mobile Computing and Networking, November 1995. An extended version appears in ACM/Baltzer Journal on Wireless Networks, December 1995.

....I TCP [1] uses a non standard Mobile IP implementation developed at Columbia University to solve mobile routing and at the same time uses two separate TCP links to provide different services for varying wireless and fixed environments. A different solution for handling mobile routing is Snoop [2] which attempts to use multicast addresses to hide the location of mobile computer. 4. Study of the effects of the mobile routing handoffs When the mobile computer moves into a new network region, mobile routing services will have to change to reflect this. These changes generally require an ....

H. Balakrishnan, S. Seshan, E. Amib and R. Kratz, Improving TCP/IP performance over wireless networks, in: Proc. of 1st Int. ACM Conf. on Mobile Computing and Networking (MOBICOM) (November 1995).

....hazards. First, from an architectural standpoint, a split TCP connection that is not explicitly associated with a proxy or a cache breaks the end to end semantics of the transport layer. Although approaches for TCP improvement over local area wireless links, such as Berkeley s snoop protocol [4] and mobile TCP [9] can preserve end to end semantics, it is more difficult to do so in the satellite environment because combating the fairness problem and speeding up slow start both rely on the early acknowledgment of data. However, steps can be taken to ensure that the connection does not ....

H. Balakrishnan, V. Padmanabhan, E. Amir, and R. Katz. Improving TCP/IP Performance over Wireless Networks. Proceedings of First ACM/IEEE MobiCom Conference, November 1995.

.... presents a brief summary of the techniques that we have investigated and our findings: To improve performance over wireless links, we have implemented a TCP aware link layer protocol called the snoop protocol that shields a TCP sender from the lossy characteristics of the wireless link [6, 7]. We have also compared this approach to a variety of other approaches for improving wireless TCP performance[4] To improve performance over asymmetric links, we have implemented techniques for eliminating the acknowledgment (ack) bottleneck that comes about as a result of bandwidth ....

....TCP performance over wireless links. In Section 4 we describe our improvements for overcoming asymmetries in network characteristics between the forward and reverse directions. In Section 5 we describe our improvements for Web traffic and conclude in Section 6. 2. The Snoop Protocol [6] Reliable transport protocols like TCP [10, 20, 8] have been tuned for traditional networks made up of wired links and stationary hosts. Due to the relatively low bit error rates over wired networks, all packet losses are assumed to be due to congestion. In the presence of the high error ....

H. Balakrishnan, S. Seshan, E. Amir, and R.H. Katz. Improving TCP/IP Performance over Wireless Networks. In Proc. 1st ACM Conf. on Mobile Computing and Networking, November 1995.

....retransmit lost packets at the link layer to hide packet loss from the sender of a TCP connection at the expense of increased delay and delay variations, and introduced packet reordering. These two schemes can be combined to improve the quality of a wireless link. Snooping Protocol (e.g. [15]) If only the last hop to a mobile host is a wireless link, a TCP aware agent can be run on the base station to snoop passing TCP packets and do some local control. For example, by caching recently transmitted TCP packets sent to a mobile host and monitoring the acknowledgment packets returning to ....

H. Balakrishnan, S. Seshan, E. Amir, R.H. Katz, Improving TCP/IP Performance over Wireless Networks, ACM MOBICOM '95.

....paper a soft state approach for controlling archive sessions. The concept of soft state has been widely used for building robust and reliable systems. A number of network protocols for Internet routing [MRR80] IP multicast routing [DEF 96] and wireless TCP optimizations such as TCP Snoop [BSAK95] use soft state to achieve scalability and good performance. We heavily rely on the 1 Submitted to NOSSDAV 98 2 use of soft state throughout our design. As we will demonstrate, this design choice has greatly simplified our fault management and availability mechanisms. The remainder of the ....

....schedule, cancel playback or perform seek or pause operations. A number of other systems outside the realm of archive control have used the notion of soft state to achieve better performance and robustness. Networking systems for routing protocols [MRR80, DEF 96] and performance optimization [BSAK95] rely on soft state to update their tables; this allows them to continue operating in the event of partial failures and ensures that no special recovery protocols are needed to regenerate state that might have been lost in a crash. A number of soft state systems such as Bayou [DPS ] have ....

H. Balakrishnan, S. Seshan, E. Amir, and R. Katz. Improving TCP/IP Performance Over Wireless Networks. In Proceedings of the first ACM Conference on Mobile Computing and Networking, Berkeley, CA, November 1995.

....bandwidth, latency, and bit error rates. The Daedalus group is developing network management software and application support services to allow mobile computers to dynamically adapt to the state of their network connectivity. The problems being examined include: improving TCP performance [BSAK95] supporting routing and handoff in heterogeneous networks, characterizing network performance, and supporting applications that are aware of the quality of their network connections and adapt to changes in this quality [Kat94] The group is also developing applications to drive the design and ....

H. Balakrishnan, S. Seshan, E. Amir, and R.H. Katz. Improving TCP/IP Performance over Wireless Networks. In Proc. 1st ACM Conf. on Mobile Computing and Networking, Berkeley, CA, November 1995. To appear.

....systems, potentially without communications at all. Using such an approach requires the devices to be manually adapted to new environments. Our conception of a proxy server is based on the model ex pressed explicitly in the Berkeley Client Proxy Server model [10] and implicitly in other work [6, 2] that places application level or network level entities near, but not at, the endpoints of communications. This is another way of thinking about Active Networks [33] driven by end to end design principles [25] push agents to as close to the endpoints as possible. This concept of leveraging the ....

BALAKRISHNAN, H., SESHAN, S., AMIR, E., AND KATZ, R. Improving TCP/IP Performance over Wireless Networks. In Proc. 1st ACM Conf. on Mobile Computing and Networking (San Franscisco, California, November 1995), pp. 2--11.

....systems, potentially without communications at all. Using such an approach requires that devices be manually adapted to new environments. Our conception of a proxy server is based on the model expressed explicitly in the Berkeley Client Proxy Server model [15] and implicitly in other work [8, 3] that places application level or network level entities near, but not at, the endpoints of communications. This is another way of thinking about Active Networks [47] driven by end to end design principles [36] push agents to as close to the endpoints as possible, but no further. This concept ....

BALAKRISHNAN, H., SESHAN, S., AMIR, E., AND KATZ, R. Improving TCP/IP Performance over Wireless Networks. In Proc. 1st ACM Conf. on Mobile Computing and Networking (San Franscisco, California, November 1995), pp. 2--11.

....systems, potentially without communications at all. Using such an approach requires that devices be manually adapted to new environments. Our conception of a proxy server is based on the model expressed explicitly in the Berkeley Client Proxy Server model [12] and implicitly in other work [6, 2] that places application level or network level entities near, but not at, the endpoints of communications. This is another way of thinking about Active Networks [41] driven by end to end design principles [31] push agents to as close to the endpoints as possible, but no further. This concept of ....

BALAKRISHNAN, H., SESHAN, S., AMIR, E., AND KATZ, R. Improving TCP/IP Performance over Wireless Networks. In Proc. 1st ACM Conf. on Mobile Computing and Networking (San Franscisco, California, November 1995), pp. 2--11.

....include implicit error recovery. The concept of soft state has been widely used for building robust and reliable systems. A number of network protocols for Internet routing [MRR80] IP multicast routing [DEF 96] and the Snoop protocol for improving TCP performance over wireless networks [BSAK95] use soft state to achieve robustness and good performance. We heavily rely on the use of soft state throughout our design. As we will demonstrate, this design choice greatly simplifies fault management resulting in high availability. Soft state protocols are also amenable to implementation on ....

....schedule, cancel playback or perform seek or pause operations. A number of other systems outside the realm of archive control have used the notion of soft state to achieve better performance and robustness. Networking systems for routing protocols [MRR80, DEF 96] and performance optimization [BSAK95] rely on soft state to update their tables; this allows them to continue operating in the event of partial failures and ensures that no special recovery protocols are needed to regenerate state that might have been lost in a crash. A number of soft state systems such as Bayou [DPS ] have ....

H. Balakrishnan, S. Seshan, E. Amir, and R. Katz. Improving TCP/IP Performance Over Wireless Networks. In Proceedings of the first ACM Conference on Mobile Computing and Networking, Berkeley, CA, November 1995.

No context found.

H. Balakrishnan, V. Padmanabhan, E. Amir, and R. Katz. Improving TCP/IP Performance over Wireless Networks. Proceedings of First ACM/IEEE MobiCom Conference, November 1995.

No context found.

H. Balakrishnan et al. Improving TCP/IP Performance over Wireless Networks. In Proc. ACM Mobicom '95, November 1995.

No context found.

H. Balakrishnan, S. Seshan, E. Amir, and R.H. Katz. Improving TCP/IP performance over wireless networks. In ACM Conference on Mobile Computing and Networking, 1995.

No context found.

H. Balakrishnan et al. Improving TCP/IP Performance over Wireless Networks. In 1st Intl. Conf. on Mobile Computing and Networking, Berkeley, CA, November 1995.

No context found.

Balakrishnan,H., Seshan, S., Amir, E., Katz, R., Improving TCP/IP Performance over Wireless Networks, 1st ACM Int'l Conf. on Mobile Computing (Mobicom), November 1995.

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