Chapter6-helmy - TC ove ATM: Pr UBR: for de lay-tole...

Info iconThis preview shows pages 1–13. Sign up to view the full content.

View Full Document Right Arrow Icon
6: Wireless and Mobile Networks 6-1 TCP over ATM: UBR: for delay-tolerant applications e.g., ftp, telnet ABR: for delay sensitive applications, e.g., on-line sessions provides explicit congestion signaling TCP over UBR: - observation: when ATM cell is dropped, all other ATM cells that belong to the same IP datagram are useless
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
6: Wireless and Mobile Networks 6-2 - solution: develop discard strategy to minimize transmission of useless cells (1) Partial Packet Discard (PPD): - when a cell is dropped at a switch, all cells belonging to the same datagram are dropped - switch identifies the end of IP datagram using type-bit in ATM header in AAL 5 - on average: ½ datagram worth of ATM cells are transmitted uselessly
Background image of page 2
6: Wireless and Mobile Networks 6-3 (2) Early Packet Discard (EPD): - when buffer exceeds a threshold, drop complete IP datragrams - problem of fairness: the shorter the datagram, the higher the probability of drop (3) add fairness using fair buffer allocation (FBA): when EPD is invoked drop from connections using more than their fair share
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
6: Wireless and Mobile Networks 6-4 - the number of VC connections is V - if N is the current occupancy, then the fair share is N/V - the weight w(i)=N(i)/[N/V], where N(i) is occupancy of connection I - policy to drop: if (N>R) and w(i)>z then drop, where R is the congestion threshold and z~1
Background image of page 4
6: Wireless and Mobile Networks 6-5
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
6: Wireless and Mobile Networks 6-6
Background image of page 6
6: Wireless and Mobile Networks 6-7 Chapter 6 Wireless and Mobile Networks Computer Networking: A Top Down Approach 4 th edition. Jim Kurose, Keith Ross Addison-Wesley, July 2007.
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
6: Wireless and Mobile Networks 6-8 Chapter 6: Wireless and Mobile Networks Background: # wireless (mobile) phone subscribers now exceeds # wired phone subscribers! computer nets: laptops, palmtops, PDAs, Internet-enabled phone promise anytime untethered Internet access two important (but different) challenges wireless: communication over wireless link mobility: handling the mobile user who changes point of attachment to network
Background image of page 8
6: Wireless and Mobile Networks 6-9 Chapter 6 outline 6.1 Introduction Wireless 6.2 Wireless links, characteristics 6.3 IEEE 802.11 wireless LANs (“wi-fi”) 6.4 Cellular Internet Access architecture standards (e.g., GSM) Mobility 6.5 Principles: addressing and routing to mobile users 6.6 Mobile IP 6.7 Handling mobility in cellular networks 6.8 Mobility and higher-layer protocols 6.9 Summary
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
6: Wireless and Mobile Networks 6-10 Elements of a wireless network network infrastructure wireless hosts laptop, PDA, IP phone run applications may be stationary (non-mobile) or mobile wireless does not always mean mobility
Background image of page 10
6: Wireless and Mobile Networks 6-11 Elements of a wireless network network infrastructure base station typically connected to wired network relay - responsible for sending packets between wired network and wireless host(s) in its “area” e.g., cell towers, 802.11 access points
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
6: Wireless and Mobile Networks 6-12 Elements of a wireless network network
Background image of page 12
Image of page 13
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 137

Chapter6-helmy - TC ove ATM: Pr UBR: for de lay-tole...

This preview shows document pages 1 - 13. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online