Bridges Store and forward device u Data link layer device u Buffers entire

Bridges store and forward device u data link layer

This preview shows page 13 - 17 out of 20 pages.

Bridges Store and forward device u Data-link layer device u Buffers entire packet and then rebroadcasts it on other ports Creates separate collision domains u Uses link-layer protocol for access to each LAN (i.e., acts like a host on that LAN) u Can accommodate different speed interfaces (issues?) u Separate CDs improves throughput (why?) Can significantly improve performance u Not all frames go everywhere. (Why did they with a hub?) CSE 123 – Lecture 7: Bridging 13
Image of page 13

Subscribe to view the full document.

Selective Forwarding Only rebroadcast a frame to the LAN where its destination resides u If A sends packet to X , then bridge must forward frame u If A sends packet to B , then bridge shouldn’t CSE 123 – Lecture 7: Bridging 14 D C B A bridge LAN 1 Z Y X W LAN 2 Who should receive a frame sent from A to Z? A. Only Z B. W, X, Y, and Z C. B, C, D, and Z D. B, C, D, W, X, Y, and Z
Image of page 14
Forwarding Tables Need to know “destination” of frame u Destination address in frame header (48bit in Ethernet) Need know which destinations are on which LANs u One approach: statically configured by hand » Table, mapping address to output port (i.e. LAN) u But we’d prefer something automatic and dynamic… Simple algorithm: Receive frame f on port q Lookup f.dest for output port /* know where to send it? */ If f.dest found then if output port is q then drop /* already delivered */ else forward f on output port; else flood f; /* forward on all ports but the one where frame arrived*/ 15 CSE 123 – Lecture 7: Bridging
Image of page 15

Subscribe to view the full document.

Learning Bridges Eliminate manual configuration by learning which addresses are on which LANs Basic approach u If a frame arrives on a port, then associate its source address with that port u
Image of page 16
Image of page 17
  • Fall '08
  • Varghese,G

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

Ask Expert Tutors You can ask 0 bonus questions You can ask 0 questions (0 expire soon) You can ask 0 questions (will expire )
Answers in as fast as 15 minutes