+ Reply to Thread
Page 1 of 3 1 23 Last
Results 1 to 25 of 71
  1. Senior Member notgoing2fail's Avatar
    Join Date
    Mar 2010
    Location
    New York
    Posts
    1,140

    Certifications
    CCNA, CCNA(Security), CSSA
    #1

    Default Packets or Frames

    Ok I figured I'd make a post about this because I think sometimes "packets" or "frames" are used interchangeably when they really shouldn't be.

    So I'm watching a video on STP and they are saying that the "packets" can continue on an endless loop unless STP is enabled.

    Over and over, they use "packets" and not "frames".

    I suppose if you want to get technical, the packets are encapsulated within frames but I really think one should use the correct terminology according to the layer in question.

    To me, when you're talking about L2 switches and the topic of STP, it's all about frames isn't it? Aren't the frames the actual items that are being switched around endlessly?

    When you talk about routers and L3, I don't hear anyone saying routers are forwarding frames, no they are pretty clear in saying packets.

    So why are "packets" used when talking about L2 related topics?


    Thoughts?
    Reply With Quote Quote  

  2. SS -->
  3. The Bringer of Light DevilWAH's Avatar
    Join Date
    Jan 2010
    Location
    UK
    Posts
    2,965

    Certifications
    CCENT, CCNA, CCNA Security, ITIL Foundation, CCNP SWITCH,ROUTE, Zoology BSc,
    #2
    actualy you will hear people say the router strips out the destination mac address from the packet, replaces it with the mac address of the next hop and sends it out the interface...

    of course what they mean is that the router replaces the mac address on the frame...

    Both routers and switch's really switch frames, a router on an Ethernet segment at least revives a frame and sends out a frame.

    I do agree that frames and packets are often used in the wrong terms, but i think often to begin with it makes more scene. most people know a PC has a ip address and you have IP packets. I know people who still find it hard to come to grips with the fact that pc's don't communicate by ip but with there mac address.

    I think once you can point out the error of people misplacing the terms then you show you understand.
    • If you can't explain it simply, you don't understand it well enough. Albert Einstein
    • An arrow can only be shot by pulling it backward. So when life is dragging you back with difficulties. It means that its going to launch you into something great. So just focus and keep aiming.
    Reply With Quote Quote  

  4. Audentis Fortuna Iuvat veritas_libertas's Avatar
    Join Date
    Feb 2009
    Posts
    5,654

    Certifications
    eCPPT, GPEN, GWAPT, GCIH, CISSP, CCNA (expired), MCTS
    #3
    This kind of confusion was very difficult for me during my associate degree studies. I wish authors and instructors/professors would be a little more exact. Then again, I guess I catch myself doing the same thing at times.
    Currently working on: Resting
    Reply With Quote Quote  

  5. Went to the dark side.... Moderator networker050184's Avatar
    Join Date
    Jul 2007
    Posts
    11,673

    Certifications
    CCNA, CCNP, CCIP, JNCIA-JUNOS, JNCIS-SP, JNCIP-SP, MCA200
    #4
    Its just one of those things you have to get used to. A lot of people just say packet or frame for everything. You could always just go with PDU if you want!
    An expert is a man who has made all the mistakes which can be made.
    Reply With Quote Quote  

  6. Skilled Hamburglar Monkerz's Avatar
    Join Date
    Apr 2010
    Location
    State of Dementia
    Posts
    832

    Certifications
    A+, Net+, CCENT, CCNA:R&S, CCNA:W, CCNP:R&S
    #5
    I guess you can look at it like this...

    A frame doesn't make it past a networking device, only a packet actually makes it past. The the layer 2 encapsulation is shed, then recreated at every intermediary device. This repackages the packet for "another leg of the journey".

    Therefore the packet would be the PDU that is sent in endless loops...

    Just my 2 cents.
    Reply With Quote Quote  

  7. Audentis Fortuna Iuvat veritas_libertas's Avatar
    Join Date
    Feb 2009
    Posts
    5,654

    Certifications
    eCPPT, GPEN, GWAPT, GCIH, CISSP, CCNA (expired), MCTS
    #6
    Quote Originally Posted by networker050184 View Post
    You could always just go with PDU if you want!
    That would certainly get their attention
    Currently working on: Resting
    Reply With Quote Quote  

  8. Senior Member alan2308's Avatar
    Join Date
    Apr 2010
    Location
    Ann Arbor, MI
    Posts
    1,809

    Certifications
    CCNA, CCNA Sec, MCSA 2008, MCSA 2012, CISSP
    #7
    Quote Originally Posted by notgoing2fail View Post
    So why are "packets" used when talking about L2 related topics?
    The same reason that people still can't tell the difference between they're, their, and there. And don't forget your/you're and our/are/hour.
    Reply With Quote Quote  

  9. Senior Member notgoing2fail's Avatar
    Join Date
    Mar 2010
    Location
    New York
    Posts
    1,140

    Certifications
    CCNA, CCNA(Security), CSSA
    #8
    haha nice response guys.....

    I guess it kinda irks me in that at the end of the day, it really doesn't matter, it's not going to be the end of the world.

    But I'm pushing myself to try to be consistent and make sure that I have a solid understanding of all the workings of a network.

    When I speak about L2, I will go out of my way to make sure I use "frames", it will help me as well as anyone else who may be confused.

    In a way, I kind of find it sloppy. Is it nitpicking? Yeah, I think a tad bit, I mean the author is a CCIE, so clearly he knows the subject and has much more game and credibility than me.

    Just something I wanted to bring up and see what you guys thought about it....
    Reply With Quote Quote  

  10. The Bringer of Light DevilWAH's Avatar
    Join Date
    Jan 2010
    Location
    UK
    Posts
    2,965

    Certifications
    CCENT, CCNA, CCNA Security, ITIL Foundation, CCNP SWITCH,ROUTE, Zoology BSc,
    #9
    Quote Originally Posted by alan2308 View Post
    The same reason that people still can't tell the difference between they're, their, and there. And don't forget your/you're and our/are/hour.
    See may be that why i don't find this a problem. suffering from being a dyslexic, i don't care if some one uses their in place of there.. to me as long as I can understand it then its fine by me

    Tihs snetcnee and tihs one are jsut the smae to me.
    this sentence and this one are just the same to me.

    I never been one who cares for the words used, I don't even really read words, just see the pictures in my head. so if some one said packet being looped around STP, in my head I have a picture of a layer 2 frame, as a picture of a naked packer at in STP is just plain wrong,
    • If you can't explain it simply, you don't understand it well enough. Albert Einstein
    • An arrow can only be shot by pulling it backward. So when life is dragging you back with difficulties. It means that its going to launch you into something great. So just focus and keep aiming.
    Reply With Quote Quote  

  11. Senior Member notgoing2fail's Avatar
    Join Date
    Mar 2010
    Location
    New York
    Posts
    1,140

    Certifications
    CCNA, CCNA(Security), CSSA
    #10
    Quote Originally Posted by DevilWAH View Post

    I never been one who cares for the words used, I don't even really read words, just see the pictures in my head. so if some one said packet being looped around STP, in my head I have a picture of a layer 2 frame, as a picture of a naked packer at in STP is just plain wrong,

    Right. I think for the majority of us, we "get" it.

    For newbies, I think it can really make learning a bit difficult and for exams, if they wanted to nitpick, they could really get you on this technicality.

    It's just something that I think if a CCIE is teaching a course, he/she should try to go out of their way to help reduce any possible confusion....
    Reply With Quote Quote  

  12. Senior Member alan2308's Avatar
    Join Date
    Apr 2010
    Location
    Ann Arbor, MI
    Posts
    1,809

    Certifications
    CCNA, CCNA Sec, MCSA 2008, MCSA 2012, CISSP
    #11
    Quote Originally Posted by DevilWAH View Post
    See may be that why i don't find this a problem. suffering from being a dyslexic, i don't care if some one uses their in place of there.. to me as long as I can understand it then its fine by me

    Tihs snetcnee and tihs one are jsut the smae to me.
    this sentence and this one are just the same to me.

    I never been one who cares for the words used, I don't even really read words, just see the pictures in my head. so if some one said packet being looped around STP, in my head I have a picture of a layer 2 frame, as a picture of a naked packer at in STP is just plain wrong,
    There's a huge difference between dyslexia and plain laziness. You're still typing in complete sentences with correct punctuation. I'd be a lot less likely to notice it then.

    But attention to detail matters, especially in this field. If you don't believe me, send out a batch of sloppy resumes or fat finger a single digit in an IP address.
    Reply With Quote Quote  

  13. Senior Member chmorin's Avatar
    Join Date
    Feb 2010
    Location
    Texas
    Posts
    1,443

    Certifications
    CCNP:Voice, CCNA:V(IIUC), CCNA, CCENT, Security +, Network +, A+,CIW
    #12
    Quote Originally Posted by alan2308 View Post
    or fat finger a single digit in an IP address.
    Been there, done that.
    Reply With Quote Quote  

  14. The Bringer of Light DevilWAH's Avatar
    Join Date
    Jan 2010
    Location
    UK
    Posts
    2,965

    Certifications
    CCENT, CCNA, CCNA Security, ITIL Foundation, CCNP SWITCH,ROUTE, Zoology BSc,
    #13
    I tell you the one that really gets me is

    Layer 3 Switch...

    hold on though... a switch is a device that runs at layer 2 of the OSI and "switchs frames"

    A router is a device that runs at layer 3 and "routes" packets

    So the term a layer 3 switch in my mind is plain wrong! should they not be called ethernet routers? but even this is wrong as they also switch..

    how about "multi layer ethernet networking devices"
    • If you can't explain it simply, you don't understand it well enough. Albert Einstein
    • An arrow can only be shot by pulling it backward. So when life is dragging you back with difficulties. It means that its going to launch you into something great. So just focus and keep aiming.
    Reply With Quote Quote  

  15. Senior Member notgoing2fail's Avatar
    Join Date
    Mar 2010
    Location
    New York
    Posts
    1,140

    Certifications
    CCNA, CCNA(Security), CSSA
    #14
    Quote Originally Posted by DevilWAH View Post
    I tell you the one that really gets me is

    Layer 3 Switch...

    hold on though... a switch is a device that runs at layer 2 of the OSI and "switchs frames"

    A router is a device that runs at layer 3 and "routes" packets

    So the term a layer 3 switch in my mind is plain wrong! should they not be called ethernet routers? but even this is wrong as they also switch..

    how about "multi layer ethernet networking devices"


    Yeah, since "switch" implies layer 2. And by calling it a L3 Switch, you're basically saying, "L3 Layer 2".

    Of course calling a device an "L3 Switch" has a cool factor sound to it.

    As someone mentioned up above, there is a slight "laziness or sloppiness" to it. I suppose if one were to pay $300-400 for a video tutorial, you'd really want to make sure that authors are using the right terms.

    I just feel bad for the new guys who take their words for it hook line and sinker. Video authors shouldn't assume the audience will just "get it", because that's bad practice.

    I'm telling you, one day some poor fool is going to get an exam question like this:

    A) A layer 2 device can switch packets at wire speed
    b) A router is a device that reduces broadcast domains
    c) All switches have the capability to route packets
    d) none of the above


    Some poor chap is going to pick "A".

    Then the exam simulator is going to say, "GOTCHYA!" A layer 2 device switches frames, not packets! hahaha.....
    Reply With Quote Quote  

  16. Went to the dark side.... Moderator networker050184's Avatar
    Join Date
    Jul 2007
    Posts
    11,673

    Certifications
    CCNA, CCNP, CCIP, JNCIA-JUNOS, JNCIS-SP, JNCIP-SP, MCA200
    #15
    Switching does not imply layer 2. Routing is packet switching. I think you guys are definitely going over board. Especially with assumptions.
    An expert is a man who has made all the mistakes which can be made.
    Reply With Quote Quote  

  17. Senior Member notgoing2fail's Avatar
    Join Date
    Mar 2010
    Location
    New York
    Posts
    1,140

    Certifications
    CCNA, CCNA(Security), CSSA
    #16
    Quote Originally Posted by networker050184 View Post
    Switching does not imply layer 2. Routing is packet switching. I think you guys are definitely going over board. Especially with assumptions.

    I thought routing was packet forwarding?
    Reply With Quote Quote  

  18. Went to the dark side.... Moderator networker050184's Avatar
    Join Date
    Jul 2007
    Posts
    11,673

    Certifications
    CCNA, CCNP, CCIP, JNCIA-JUNOS, JNCIS-SP, JNCIP-SP, MCA200
    #17
    Quote Originally Posted by notgoing2fail View Post
    I thought routing was packet forwarding?

    Thats just it, more than one way to skin a cat. Doesn't mean one way is wrong.
    An expert is a man who has made all the mistakes which can be made.
    Reply With Quote Quote  

  19. Senior Member notgoing2fail's Avatar
    Join Date
    Mar 2010
    Location
    New York
    Posts
    1,140

    Certifications
    CCNA, CCNA(Security), CSSA
    #18
    Quote Originally Posted by networker050184 View Post
    Thats just it, more than one way to skin a cat. Doesn't mean one way is wrong.

    I thought that you could get away with "packet switching" when you have routers with actual switching capabilities like with IP CEF enabled.

    If you turn off IP CEF/ip route cache and all processing is done at the route processor, is it fair to say that packets are now forwarded since they are never switched at the switching engine?
    Reply With Quote Quote  

  20. Senior Member chmorin's Avatar
    Join Date
    Feb 2010
    Location
    Texas
    Posts
    1,443

    Certifications
    CCNP:Voice, CCNA:V(IIUC), CCNA, CCENT, Security +, Network +, A+,CIW
    #19
    Quote Originally Posted by networker050184 View Post
    Thats just it, more than one way to skin a cat. Doesn't mean one way is wrong.
    Could this be a case of a square is a rectangle, but a rectangle is not a square?

    Muaahhahah. This is one of those topics that if you think to hard about it, you are going to get confused. Break out packet tracer and follow the packet from hop to hop. You get to see what changes in the frame and packet if I remember correctly.
    Reply With Quote Quote  

  21. Went to the dark side.... Moderator networker050184's Avatar
    Join Date
    Jul 2007
    Posts
    11,673

    Certifications
    CCNA, CCNP, CCIP, JNCIA-JUNOS, JNCIS-SP, JNCIP-SP, MCA200
    #20
    Switching has nothing to do with the layer. Its just a name for having a packet/frame come in one interface and have it "switched" out another interface. That is all it means. Nothing to do with the routers architecture.
    An expert is a man who has made all the mistakes which can be made.
    Reply With Quote Quote  

  22. chX
    chX is offline
    Member
    Join Date
    Jun 2010
    Location
    Adelaide, Australia
    Posts
    96

    Certifications
    CCNA
    #21
    I read once something similar to:

    The process of receiving a packet on one interface, making a decision about what to do with it, and emitting it on another interface is not routing, it's switching.

    Routing is what OSPF, BGP, RIP, etc, do. Which is populating the routing table with information which can be used to make a switching decision.

    Interesting way to look at it.
    Last edited by chX; 06-30-2010 at 03:11 PM.
    Reply With Quote Quote  

  23. cisco noob fly351's Avatar
    Join Date
    Mar 2010
    Location
    TN
    Posts
    357

    Certifications
    CCNA, Net+, A+
    #22
    Quote Originally Posted by DevilWAH View Post
    I tell you the one that really gets me is

    Layer 3 Switch...

    hold on though... a switch is a device that runs at layer 2 of the OSI and "switchs frames"

    A router is a device that runs at layer 3 and "routes" packets

    So the term a layer 3 switch in my mind is plain wrong! should they not be called ethernet routers? but even this is wrong as they also switch..

    how about "multi layer ethernet networking devices"
    I am pretty sure a Layer 3 switch is still considered a switch because of how it compiles a TCAM table, which a router does not. Single table look ups vs multi-table look ups.
    Reply With Quote Quote  

  24. cisco noob fly351's Avatar
    Join Date
    Mar 2010
    Location
    TN
    Posts
    357

    Certifications
    CCNA, Net+, A+
    #23
    Quote Originally Posted by chX View Post
    I read once something similar to:

    - Switching is receiving a frame/packet/whatever on one interface, making a decision about what to do with it and sending it out another inteface, and;

    - Routing is what OSPF, BGP, RIP, etc, do. Which is filling the routing table with information which can be used to make a switching decision.

    Interesting way to look at it.
    But if you look at what you just said... basically that boils down to...

    "Switching forwards"
    "Routing forwards"

    So what is the difference?
    Reply With Quote Quote  

  25. Senior Member chmorin's Avatar
    Join Date
    Feb 2010
    Location
    Texas
    Posts
    1,443

    Certifications
    CCNP:Voice, CCNA:V(IIUC), CCNA, CCENT, Security +, Network +, A+,CIW
    #24
    Quote Originally Posted by fly351 View Post
    But if you look at what you just said... basically that boils down to...

    "Switching forwards"
    "Routing forwards"

    So what is the difference?
    The end does not define the means.

    Switching and routing have different tools and different algorithms associated with each set in order to accomplish the task that they are assigned. A hub forwards too, but it certainly is no router. It is the decision making process that decides the term.
    Reply With Quote Quote  

  26. chX
    chX is offline
    Member
    Join Date
    Jun 2010
    Location
    Adelaide, Australia
    Posts
    96

    Certifications
    CCNA
    #25
    Quote Originally Posted by fly351 View Post
    But if you look at what you just said... basically that boils down to...

    "Switching forwards"
    "Routing forwards"

    So what is the difference?
    I've edited my post a little bit.

    At the end of the day I see it as:

    A layer 2 Ethernet switch (since you can have ATM/FR/MPLS switches, right?) moves frames around a LAN based on Layer2 addressing.

    A router separates and interconnects networks and stops broadcasts (by default). It can make switching decisions based on routing information it acquires.

    A layer 3 switch is a layer 2 switch with routing capabilities, or perhaps you could say a router with a lot more ports.


    That's my fairly narrow view, purely from the networking I've been exposed to so far.
    Last edited by chX; 06-30-2010 at 03:33 PM.
    Reply With Quote Quote  

+ Reply to Thread
Page 1 of 3 1 23 Last

Social Networking & Bookmarks