| 1. |
- Eklund, Johan, 1966-, et al.
(författare)
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Tuning SCTP failover for carrier grade telephony signaling
- 2010
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Ingår i: Computer Networks. - : Elsevier BV. - 1389-1286 .- 1872-7069. ; 54:1, s. 133-149
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Tidskriftsartikel (refereegranskat)abstract
- The Stream Control Transmission Protocol (SCTP) has not only been selected as the signaling transport protocol of choice in IETF SIGTRAN, the architecture that bridges circuit-switched and IP-based mobile core networks, but also plays a pivotal role in SAE/LTE, the next-generation UMTS/HSPA networks. To meet the redundancy requirements of telecom signaling traffic, SCTP includes a failover mechanism that enables rerouting of traffic from an unreachable network path to a backup path. However, the recommendations provided by IETF on how to configure the SCTP failover mechanism to meet telecom signaling requirements are kept quite general and leave much of the tuning to the telecom equipment vendor and/or operator. Several works by us and others have been carried out to study the effect of different SCTP parameters on the failover performance. The main contribution of this paper is that it gives a coherent treatment of how to configure the SCTP failover mechanism for carrier-grade telephony signaling, and provides practically usable configuration recommendations. The paper also discusses an alternate or complementary way of optimizing the SCTP failover mechanism by relaxing the exponential backoff that foregoes a retransmission timeout in SCTP. Some results showing significantly reduced failover times by use of this mechanism, with only marginal deteriorating effects on a signaling network, are discussed and analyzed in the paper. (C) 2009 Elsevier B.V. All rights reserved.
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| 2. |
- Hurtig, Per, 1980-, et al.
(författare)
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Recent Trends in TCP Packet-Level Characteristics
- 2011
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Ingår i: International Conference on Networking and Services (ICNS '11). - Venice/Mestre, Italy : IARIA. - 9781612080062 - 9781612081335
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Konferensbidrag (refereegranskat)abstract
- Up-to-date TCP traffic characteristics are essential for research and development of protocols and applications.This paper presents recent trends observed in 70 measurements on backbone links from 2006 and 2009. First, we provide general characteristics such as packet size distributions and TCP option usage. We confirm previous observations such as the dominance of TCP as transport and higher utilization of TCP options. Next, we look at out-of-sequence (OOS) TCP segments. OOS segments often have negative effects on TCP performance, and therefore require special consideration. While the total fraction of OOS segments is stable in our measurements, we observe a significant decrease in OOS due to packet reordering (from 22.5% to 5.2% of all OOS segments). We verify that this development is a general trend in our measurements and not caused by single hosts/networks or special temporal events. Our findings are surprising as many researchers previously have speculated in an increased amount of reordering.
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| 3. |
- Lindskog, Stefan, 1967-, et al.
(författare)
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Data Protection based on Physical Separation : Concepts and Application Scenarios
- 2005
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Ingår i: Computational Science and Its Applications. - Berlin : Springer. - 9783540258636 ; , s. 1331-1340
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Konferensbidrag (refereegranskat)abstract
- Data protection is an increasingly important issue in today's communication networks. Traditional solutions for protecting data when transferred over a network are almost exclusively based on cryptography. As a complement, we propose the use of multiple physically separate paths to accomplish data protection. A general concept for providing physical separation of data streams together with a threat model is presented. The main target is delay-sensitive applications such as telephony signaling, live TV, and radio broadcasts that require only lightweight security. The threat considered is malicious interception of network transfers through so-called eavesdropping attacks. Application scenarios and techniques to provide physically separate paths are discussed
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| 4. |
- Lindskog, Stefan, 1967-, et al.
(författare)
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Physical Separation for Data Protection based on SCTP Multihoming
- 2004
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Ingår i: Proceedings of the Second Swedish National Computer Networking Workshop. - Karlstad.
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Konferensbidrag (refereegranskat)abstract
- Network security is an increasingly important issue. Traditional solutions for protecting data when transferred over the network are almost exclusively based on cryptography. As a complement, we propose the use of SCTP and its support for physically separate paths to accomplish protection against eavesdropping attacks near the end points.
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| 5. |
- Alfredsson, Stefan, 1976-, et al.
(författare)
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A 4G Link Level Emulator for Transport Protocol Evaluation
- 2004
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Ingår i: Proceedings of The Second Swedish National Computer Networking Workshop (SNCNW). ; , s. 19-23
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Konferensbidrag (refereegranskat)abstract
- This paper presents a wireless link and networkemulator, based upon the "Wireless IP" 4G system proposalfrom Uppsala University and partners. In wireless fading down-links (base to terminals) link-level frames are scheduled andthe transmission is adapted on a fast time scale. With fastlink adaptation and fast link level retransmission, the fading properties of wireless links can to a large extent be counteractedat the physical and link layers. A purpose of the emulatoris to investigate the resulting interaction with transport layer protocols. The emulator is built on Internet technologies, andis installed as a gateway between communicating hosts. The paper gives an overview of the emulator design, and presentspreliminary experiments with three different TCP variants. The results illustrate the functionality of the emulator by showing theeffect of changing link layer parameters on the different TCP variants.
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| 6. |
- Alfredsson, Stefan, 1976-, et al.
(författare)
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Bit Error Tolerant Multimedia Transport
- 2004
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Ingår i: Perspectives on Multimedia. - Chichester : John Wiley & Sons. - 9780470868638 ; , s. 175-191
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 7. |
- Alfredsson, Stefan, 1976-, et al.
(författare)
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Cross-layer analysis of TCP performance in a 4G system
- 2007
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Ingår i: Proceedings of the 15th International Conference on Software, Telecommunications and Computer Networks. - : IEEE Computer Society. - 953611495X - 9789536114931
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Konferensbidrag (refereegranskat)abstract
- This paper presents results from an experimental study of TCP in a wireless 4G evaluation system. Test-bed results on transport layer performance are presented and analyzed in relation to several link layer aspects. The aspects investigated are the impact of channel prediction errors, channel scheduling, delay, and adaptive modulation switch level, on TCP performance. The paper contributes a cross-layer analysis of the interaction between symbol modulation levels, different scheduling strategies, channel prediction errors and the resulting frame retransmissions effect on TCP. The paper also shows that highly persistent ARQ with fast link retransmissions do not interact negatively with the TCP retransmission timer even for short round trip delays.
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| 8. |
- Alfredsson, Stefan, 1976-, et al.
(författare)
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Emulation and Validation of a 4G System Proposal
- 2005
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Ingår i: Proceedings of RadioVetenskap och Kommunikation 2005. - 9170561222 ; , s. 357-362
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Konferensbidrag (refereegranskat)abstract
- This paper presents a wireless link and network emulator,along with experiments and validation against the "Wireless IP" 4G system proposal from Uppsala University and partners. In wireless fading downlinks (base to terminals) link-level frames are scheduled and the transmission is adapted on a fast time scale. With fast link adaptation and fast link level retransmission, the fading properties of wireless links can to a large extent be counteracted at thephysical and link layers. The emulator has been used to experimentally investigate the resulting interaction between the transport layer and the link layer. The paper gives an overview of the emulator design, and presents experimental results with three different TCP variants in combination with various link layer characteristics.
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| 9. |
- Alfredsson, Stefan, 1976-, et al.
(författare)
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Impact of 4G Wireless Link Configurations on VoIP Network Performance
- 2008
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Ingår i: Proceedings of the 2008 IEEE International Symposium on Wireless Communication Systems. - : IEEE Communications Society. - 9781424424894 - 9781424424887 ; , s. 708-712
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Konferensbidrag (refereegranskat)abstract
- The performance of applications in wireless networks is partly dependent upon the link configuration. Link characteristics varies with frame retransmission persistency, link frame retransmission delay, adaptive modulation strategies, coding, and more. The link configuration and channel conditions can lead to packet loss, delay and delay variations, which impact different applications in different ways. A bulk transfer application may tolerate delays to a large extent, while packet loss is undesirable. On the other hand, real-time interactive applications are sensitive to delay and delay variations, but may tolerate packet loss to a certain extent. This paper contributes a study of the effect of link frame retransmission persistency and delay on packet loss and latency for real-time interactive applications. The results indicate that a reliable retransmission mechanism with fast link retransmissions in the range of 2-8 ms is sufficient to provide an upper delay bound of 50 ms over the wireless link, which is well within the delay budget of voice over IP applications.
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| 10. |
- Alfredsson, Stefan, 1976-, et al.
(författare)
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TCP-L : Allowing Bit Errors in Wireless TCP
- 2003
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Ingår i: Proceedings of the 12th IST Summit on Mobile and Wireless Communications. - : Institute for Operations Research and the Management Sciences (INFORMS). - 9729836817 ; , s. 149-154
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Konferensbidrag (refereegranskat)abstract
- This paper presents a technique to improve the performance of TCP and the utilization of wireless networks.Wireless links exhibit high rates of bit errors, compared to communication over wireline or fiber. Since TCP cannotseparate packet losses due to bit errors versus congestion,all losses are treated as signs of congestion and congestionavoidance is initiated. This paper explores the possibility of accepting TCP packets with an erroneous checksum, toimprove network performance for those applications that can tolerate bit errors. Since errors may be in the TCP header aswell as the payload, the possibility of recovering the headeris discussed. An algorithm for this recovery is also presented.Experiments with an implementation have been performed,which show that large improvements in throughput can beachieved, depending on link and error characteristics.
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