{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

lecture_21_bridges

lecture_21_bridges - andComputerNetworks Lecture 21 Bridges...

Info icon This preview shows pages 1–12. Sign up to view the full content.

View Full Document Right Arrow Icon
CS 536 Data Communica0ons and Computer Networks Lecture 21: Bridges and Switches 11/25/2008 Some slides courtesy George Varghese and Nick McKeown 1 CS536 : Computer Networks
Image of page 1

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

View Full Document Right Arrow Icon
Link Layer 5.1 Introduction and services 5.2 Error detection and correction 5.3 Multiple access protocols 5.4 Link-layer Addressing 5.5 Ethernet 5.6 Link-layer switches 5.7 PPP 5.8 Link Virtualization: ATM, MPLS 2 CS536 : Computer Networks
Image of page 2
Hubs … physical-layer (“dumb”) repeaters: bits coming in one link go out all other links at same rate all nodes connected to hub can collide with one another no frame buffering no CSMA/CD at hub: host NICs detect collisions twisted pair hub 3 CS536 : Computer Networks
Image of page 3

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

View Full Document Right Arrow Icon
Bridges (precursor to switches) Circa 1980 at DEC: Ethernets under attack Ethernet had limited distance (2.5km) and limited number of stations (8000) Perception that Ethernet collapsed under high loads. Question: How to extend 2 Ethernets to make a larger ethernet that has twice the distance, bandwidth and # of stations. 4 CS536 : Computer Networks
Image of page 4
Bridges Solution 1: Use repeaters Does not work since repeaters/hubs repeat each and every bit, so every node still part of the collision domain. Solution 2: Use routers Routers are expensive Many routers are required if want to interconnect several types of LANs (XEROX, DEC, etc.) Main problem : How to extend LANs transparently. 5 CS536 : Computer Networks
Image of page 5

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

View Full Document Right Arrow Icon
Bridge Basic idea: Learn the locations of individual machines and selectively repeat frames A B C D Bridge 6 CS536 : Computer Networks
Image of page 6
Code 7 CS536 : Computer Networks
Image of page 7

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

View Full Document Right Arrow Icon
Bridge Generaliza0ons Any LAN or Data Link that puts both source and destination addresses in frames (includes all types of 802 LANs) Any topology that has no cycles More than two bridge ports. 8 CS536 : Computer Networks
Image of page 8
Realiza0on Need much higher performance than router which handles only frames address to it Need to make decision with 51.2usec on each port. First DEC implementation by Mark Kempf using 1984 technology. Achieved forwarding in min frame time within 1000$s. 9 CS536 : Computer Networks
Image of page 9

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

View Full Document Right Arrow Icon
Basic architecture 3 bus design to avoid congestion on Proc Bus 4 port memory design Hardware Binary Search takes log (8K)=13 memory accesses of 100nsec ~ 1.3 usec Processor stays in loop after a packet interrupt servicing as many packets to reduce context switching overheads 10 CS536 : Computer Networks
Image of page 10
Switch (new versions of bridges)
Image of page 11

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

View Full Document Right Arrow Icon
Image of page 12
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern