Does a router send frames or packets?












2















Perhaps it's a novice question, but does a router send/receive frames?
When I read about this subject, it seems that routers decapsulate the frame on arrival, and encapsulate the packet in a frame in order to send it.



But why do people talk about packets forwarding? Also, when you ping a domain name, you have "packets transmitted, received".
Is it an abuse of language?



So, if I eavesdrop the link between two routers, do I see frames (with MAC addresses) or packets ?



Thanks !










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  • 1





    Unless the packet is large enough to require fragmentation, there's usually a one-to-one correspondence between packets and frames.

    – Barmar
    3 hours ago











  • A router (with an Ethernet interface) sends packets inside of frames. This is what "encapsulation" is about.

    – chrylis
    57 mins ago
















2















Perhaps it's a novice question, but does a router send/receive frames?
When I read about this subject, it seems that routers decapsulate the frame on arrival, and encapsulate the packet in a frame in order to send it.



But why do people talk about packets forwarding? Also, when you ping a domain name, you have "packets transmitted, received".
Is it an abuse of language?



So, if I eavesdrop the link between two routers, do I see frames (with MAC addresses) or packets ?



Thanks !










share|improve this question









New contributor




Smbbo is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
















  • 1





    Unless the packet is large enough to require fragmentation, there's usually a one-to-one correspondence between packets and frames.

    – Barmar
    3 hours ago











  • A router (with an Ethernet interface) sends packets inside of frames. This is what "encapsulation" is about.

    – chrylis
    57 mins ago














2












2








2








Perhaps it's a novice question, but does a router send/receive frames?
When I read about this subject, it seems that routers decapsulate the frame on arrival, and encapsulate the packet in a frame in order to send it.



But why do people talk about packets forwarding? Also, when you ping a domain name, you have "packets transmitted, received".
Is it an abuse of language?



So, if I eavesdrop the link between two routers, do I see frames (with MAC addresses) or packets ?



Thanks !










share|improve this question









New contributor




Smbbo is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.












Perhaps it's a novice question, but does a router send/receive frames?
When I read about this subject, it seems that routers decapsulate the frame on arrival, and encapsulate the packet in a frame in order to send it.



But why do people talk about packets forwarding? Also, when you ping a domain name, you have "packets transmitted, received".
Is it an abuse of language?



So, if I eavesdrop the link between two routers, do I see frames (with MAC addresses) or packets ?



Thanks !







routing router layer2 layer3 icmp






share|improve this question









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share|improve this question









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share|improve this question








edited 6 hours ago









Ron Maupin

64.4k1367120




64.4k1367120






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asked 9 hours ago









SmbboSmbbo

111




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  • 1





    Unless the packet is large enough to require fragmentation, there's usually a one-to-one correspondence between packets and frames.

    – Barmar
    3 hours ago











  • A router (with an Ethernet interface) sends packets inside of frames. This is what "encapsulation" is about.

    – chrylis
    57 mins ago














  • 1





    Unless the packet is large enough to require fragmentation, there's usually a one-to-one correspondence between packets and frames.

    – Barmar
    3 hours ago











  • A router (with an Ethernet interface) sends packets inside of frames. This is what "encapsulation" is about.

    – chrylis
    57 mins ago








1




1





Unless the packet is large enough to require fragmentation, there's usually a one-to-one correspondence between packets and frames.

– Barmar
3 hours ago





Unless the packet is large enough to require fragmentation, there's usually a one-to-one correspondence between packets and frames.

– Barmar
3 hours ago













A router (with an Ethernet interface) sends packets inside of frames. This is what "encapsulation" is about.

– chrylis
57 mins ago





A router (with an Ethernet interface) sends packets inside of frames. This is what "encapsulation" is about.

– chrylis
57 mins ago










3 Answers
3






active

oldest

votes


















6















it seems that routers decapsulate the frame on arrival, and
encapsulate the packet in a frame in order to send it.




Yes. A router must strip off the layer-2 frame in order to get to the layer-3 packet. The router then routes the packet to the next interface toward the destination, based on the layer-3 destination address. At the next interface, it must build a new frame for the packet for the layer-2 protocol on the next interface, which could be a completely different layer-2 protocol than the one used on the first interface.




But why people talk about packets forwarding ?




That is what the router is doing. It forwards packets from one interface to another interface (one network to another network).




Also, when you ping a domain name, you have "packets transmitted,
received". Is it an abuse of language?




No. Ping is an application that uses ICMP echo requests and replies, and ICMP is an integral part of IP, which is a layer-3 protocol that uses packets.




So, if I eavesdrop the link between two routers, do I see frames (with
mac addresses) or packets ?




Not all layer-2 protocols use MAC addresses, Only the IEEE LAN protocols use MAC addresses. Often, the layer-2 connection between routers will use something like PPP, which has no addressing on the layer-2 frames because there are only two possible endpoints. If the connection between the two routers is an IEEE protocol, then, yes, you will see frames with MAC addresses. If it is frame relay, you will see frames with DLCIs; with ATM, you will see frames with VPI/VCI; etc.






share|improve this answer

































    2














    In the case of eavesdropping a web fetch over an ethernet-connected router, you could consider yourself to be looking at voltages, bits, bytes, frames, packets, segments, streams, or pages.



    For an analogy, consider whether you hear words or sounds when someone speaks to you. Obviously, it's both, and which you focus on depends on what you're thinking about.






    share|improve this answer































      0















      Perhaps it's a novice question, but does a router send/receive frames?




      Yes




      When I read about this subject, it seems that routers decapsulate the
      frame on arrival, and encapsulate the packet in a frame in order to
      send it.




      That is correct. L2 router needs to decapsulate packet data from it's framing headers (and trailers) on source port, then reencapsulate it in another frame for sending on outgoing port.
      That's because frame headers will change (for example, router might receive Ethernet II frame on one port, decapsulate packet data, and reencapsulate with different source MAC and checksum before sending it on outgoing port).



      Also, input and output ports could be of different type, so entirely different frame (like for example Frame relay could be constructed, but it will still hold the same payload ("packet data")




      But why do people talk about packets forwarding? Also, when you ping a
      domain name, you have "packets transmitted, received". Is it an abuse
      of language?




      More like ambiguity of language. You can view Network packet and Frame as synonyms. Or you can use "packet" to mean frame payload (that is just "packet data" from frame, as in for example commonly used "TCP/IP packet").




      So, if I eavesdrop the link between two routers, do I see frames (with
      MAC addresses) or packets ?




      You would see complete frames, including it's headers (like source/destination MAC on Ethernet)






      share|improve this answer








      New contributor




      Matija Nalis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.




















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        3 Answers
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        3 Answers
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        6















        it seems that routers decapsulate the frame on arrival, and
        encapsulate the packet in a frame in order to send it.




        Yes. A router must strip off the layer-2 frame in order to get to the layer-3 packet. The router then routes the packet to the next interface toward the destination, based on the layer-3 destination address. At the next interface, it must build a new frame for the packet for the layer-2 protocol on the next interface, which could be a completely different layer-2 protocol than the one used on the first interface.




        But why people talk about packets forwarding ?




        That is what the router is doing. It forwards packets from one interface to another interface (one network to another network).




        Also, when you ping a domain name, you have "packets transmitted,
        received". Is it an abuse of language?




        No. Ping is an application that uses ICMP echo requests and replies, and ICMP is an integral part of IP, which is a layer-3 protocol that uses packets.




        So, if I eavesdrop the link between two routers, do I see frames (with
        mac addresses) or packets ?




        Not all layer-2 protocols use MAC addresses, Only the IEEE LAN protocols use MAC addresses. Often, the layer-2 connection between routers will use something like PPP, which has no addressing on the layer-2 frames because there are only two possible endpoints. If the connection between the two routers is an IEEE protocol, then, yes, you will see frames with MAC addresses. If it is frame relay, you will see frames with DLCIs; with ATM, you will see frames with VPI/VCI; etc.






        share|improve this answer






























          6















          it seems that routers decapsulate the frame on arrival, and
          encapsulate the packet in a frame in order to send it.




          Yes. A router must strip off the layer-2 frame in order to get to the layer-3 packet. The router then routes the packet to the next interface toward the destination, based on the layer-3 destination address. At the next interface, it must build a new frame for the packet for the layer-2 protocol on the next interface, which could be a completely different layer-2 protocol than the one used on the first interface.




          But why people talk about packets forwarding ?




          That is what the router is doing. It forwards packets from one interface to another interface (one network to another network).




          Also, when you ping a domain name, you have "packets transmitted,
          received". Is it an abuse of language?




          No. Ping is an application that uses ICMP echo requests and replies, and ICMP is an integral part of IP, which is a layer-3 protocol that uses packets.




          So, if I eavesdrop the link between two routers, do I see frames (with
          mac addresses) or packets ?




          Not all layer-2 protocols use MAC addresses, Only the IEEE LAN protocols use MAC addresses. Often, the layer-2 connection between routers will use something like PPP, which has no addressing on the layer-2 frames because there are only two possible endpoints. If the connection between the two routers is an IEEE protocol, then, yes, you will see frames with MAC addresses. If it is frame relay, you will see frames with DLCIs; with ATM, you will see frames with VPI/VCI; etc.






          share|improve this answer




























            6












            6








            6








            it seems that routers decapsulate the frame on arrival, and
            encapsulate the packet in a frame in order to send it.




            Yes. A router must strip off the layer-2 frame in order to get to the layer-3 packet. The router then routes the packet to the next interface toward the destination, based on the layer-3 destination address. At the next interface, it must build a new frame for the packet for the layer-2 protocol on the next interface, which could be a completely different layer-2 protocol than the one used on the first interface.




            But why people talk about packets forwarding ?




            That is what the router is doing. It forwards packets from one interface to another interface (one network to another network).




            Also, when you ping a domain name, you have "packets transmitted,
            received". Is it an abuse of language?




            No. Ping is an application that uses ICMP echo requests and replies, and ICMP is an integral part of IP, which is a layer-3 protocol that uses packets.




            So, if I eavesdrop the link between two routers, do I see frames (with
            mac addresses) or packets ?




            Not all layer-2 protocols use MAC addresses, Only the IEEE LAN protocols use MAC addresses. Often, the layer-2 connection between routers will use something like PPP, which has no addressing on the layer-2 frames because there are only two possible endpoints. If the connection between the two routers is an IEEE protocol, then, yes, you will see frames with MAC addresses. If it is frame relay, you will see frames with DLCIs; with ATM, you will see frames with VPI/VCI; etc.






            share|improve this answer
















            it seems that routers decapsulate the frame on arrival, and
            encapsulate the packet in a frame in order to send it.




            Yes. A router must strip off the layer-2 frame in order to get to the layer-3 packet. The router then routes the packet to the next interface toward the destination, based on the layer-3 destination address. At the next interface, it must build a new frame for the packet for the layer-2 protocol on the next interface, which could be a completely different layer-2 protocol than the one used on the first interface.




            But why people talk about packets forwarding ?




            That is what the router is doing. It forwards packets from one interface to another interface (one network to another network).




            Also, when you ping a domain name, you have "packets transmitted,
            received". Is it an abuse of language?




            No. Ping is an application that uses ICMP echo requests and replies, and ICMP is an integral part of IP, which is a layer-3 protocol that uses packets.




            So, if I eavesdrop the link between two routers, do I see frames (with
            mac addresses) or packets ?




            Not all layer-2 protocols use MAC addresses, Only the IEEE LAN protocols use MAC addresses. Often, the layer-2 connection between routers will use something like PPP, which has no addressing on the layer-2 frames because there are only two possible endpoints. If the connection between the two routers is an IEEE protocol, then, yes, you will see frames with MAC addresses. If it is frame relay, you will see frames with DLCIs; with ATM, you will see frames with VPI/VCI; etc.







            share|improve this answer














            share|improve this answer



            share|improve this answer








            edited 6 hours ago

























            answered 9 hours ago









            Ron MaupinRon Maupin

            64.4k1367120




            64.4k1367120























                2














                In the case of eavesdropping a web fetch over an ethernet-connected router, you could consider yourself to be looking at voltages, bits, bytes, frames, packets, segments, streams, or pages.



                For an analogy, consider whether you hear words or sounds when someone speaks to you. Obviously, it's both, and which you focus on depends on what you're thinking about.






                share|improve this answer




























                  2














                  In the case of eavesdropping a web fetch over an ethernet-connected router, you could consider yourself to be looking at voltages, bits, bytes, frames, packets, segments, streams, or pages.



                  For an analogy, consider whether you hear words or sounds when someone speaks to you. Obviously, it's both, and which you focus on depends on what you're thinking about.






                  share|improve this answer


























                    2












                    2








                    2







                    In the case of eavesdropping a web fetch over an ethernet-connected router, you could consider yourself to be looking at voltages, bits, bytes, frames, packets, segments, streams, or pages.



                    For an analogy, consider whether you hear words or sounds when someone speaks to you. Obviously, it's both, and which you focus on depends on what you're thinking about.






                    share|improve this answer













                    In the case of eavesdropping a web fetch over an ethernet-connected router, you could consider yourself to be looking at voltages, bits, bytes, frames, packets, segments, streams, or pages.



                    For an analogy, consider whether you hear words or sounds when someone speaks to you. Obviously, it's both, and which you focus on depends on what you're thinking about.







                    share|improve this answer












                    share|improve this answer



                    share|improve this answer










                    answered 8 hours ago









                    jonathanjojonathanjo

                    11.4k1934




                    11.4k1934























                        0















                        Perhaps it's a novice question, but does a router send/receive frames?




                        Yes




                        When I read about this subject, it seems that routers decapsulate the
                        frame on arrival, and encapsulate the packet in a frame in order to
                        send it.




                        That is correct. L2 router needs to decapsulate packet data from it's framing headers (and trailers) on source port, then reencapsulate it in another frame for sending on outgoing port.
                        That's because frame headers will change (for example, router might receive Ethernet II frame on one port, decapsulate packet data, and reencapsulate with different source MAC and checksum before sending it on outgoing port).



                        Also, input and output ports could be of different type, so entirely different frame (like for example Frame relay could be constructed, but it will still hold the same payload ("packet data")




                        But why do people talk about packets forwarding? Also, when you ping a
                        domain name, you have "packets transmitted, received". Is it an abuse
                        of language?




                        More like ambiguity of language. You can view Network packet and Frame as synonyms. Or you can use "packet" to mean frame payload (that is just "packet data" from frame, as in for example commonly used "TCP/IP packet").




                        So, if I eavesdrop the link between two routers, do I see frames (with
                        MAC addresses) or packets ?




                        You would see complete frames, including it's headers (like source/destination MAC on Ethernet)






                        share|improve this answer








                        New contributor




                        Matija Nalis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
                        Check out our Code of Conduct.

























                          0















                          Perhaps it's a novice question, but does a router send/receive frames?




                          Yes




                          When I read about this subject, it seems that routers decapsulate the
                          frame on arrival, and encapsulate the packet in a frame in order to
                          send it.




                          That is correct. L2 router needs to decapsulate packet data from it's framing headers (and trailers) on source port, then reencapsulate it in another frame for sending on outgoing port.
                          That's because frame headers will change (for example, router might receive Ethernet II frame on one port, decapsulate packet data, and reencapsulate with different source MAC and checksum before sending it on outgoing port).



                          Also, input and output ports could be of different type, so entirely different frame (like for example Frame relay could be constructed, but it will still hold the same payload ("packet data")




                          But why do people talk about packets forwarding? Also, when you ping a
                          domain name, you have "packets transmitted, received". Is it an abuse
                          of language?




                          More like ambiguity of language. You can view Network packet and Frame as synonyms. Or you can use "packet" to mean frame payload (that is just "packet data" from frame, as in for example commonly used "TCP/IP packet").




                          So, if I eavesdrop the link between two routers, do I see frames (with
                          MAC addresses) or packets ?




                          You would see complete frames, including it's headers (like source/destination MAC on Ethernet)






                          share|improve this answer








                          New contributor




                          Matija Nalis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
                          Check out our Code of Conduct.























                            0












                            0








                            0








                            Perhaps it's a novice question, but does a router send/receive frames?




                            Yes




                            When I read about this subject, it seems that routers decapsulate the
                            frame on arrival, and encapsulate the packet in a frame in order to
                            send it.




                            That is correct. L2 router needs to decapsulate packet data from it's framing headers (and trailers) on source port, then reencapsulate it in another frame for sending on outgoing port.
                            That's because frame headers will change (for example, router might receive Ethernet II frame on one port, decapsulate packet data, and reencapsulate with different source MAC and checksum before sending it on outgoing port).



                            Also, input and output ports could be of different type, so entirely different frame (like for example Frame relay could be constructed, but it will still hold the same payload ("packet data")




                            But why do people talk about packets forwarding? Also, when you ping a
                            domain name, you have "packets transmitted, received". Is it an abuse
                            of language?




                            More like ambiguity of language. You can view Network packet and Frame as synonyms. Or you can use "packet" to mean frame payload (that is just "packet data" from frame, as in for example commonly used "TCP/IP packet").




                            So, if I eavesdrop the link between two routers, do I see frames (with
                            MAC addresses) or packets ?




                            You would see complete frames, including it's headers (like source/destination MAC on Ethernet)






                            share|improve this answer








                            New contributor




                            Matija Nalis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
                            Check out our Code of Conduct.











                            Perhaps it's a novice question, but does a router send/receive frames?




                            Yes




                            When I read about this subject, it seems that routers decapsulate the
                            frame on arrival, and encapsulate the packet in a frame in order to
                            send it.




                            That is correct. L2 router needs to decapsulate packet data from it's framing headers (and trailers) on source port, then reencapsulate it in another frame for sending on outgoing port.
                            That's because frame headers will change (for example, router might receive Ethernet II frame on one port, decapsulate packet data, and reencapsulate with different source MAC and checksum before sending it on outgoing port).



                            Also, input and output ports could be of different type, so entirely different frame (like for example Frame relay could be constructed, but it will still hold the same payload ("packet data")




                            But why do people talk about packets forwarding? Also, when you ping a
                            domain name, you have "packets transmitted, received". Is it an abuse
                            of language?




                            More like ambiguity of language. You can view Network packet and Frame as synonyms. Or you can use "packet" to mean frame payload (that is just "packet data" from frame, as in for example commonly used "TCP/IP packet").




                            So, if I eavesdrop the link between two routers, do I see frames (with
                            MAC addresses) or packets ?




                            You would see complete frames, including it's headers (like source/destination MAC on Ethernet)







                            share|improve this answer








                            New contributor




                            Matija Nalis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
                            Check out our Code of Conduct.









                            share|improve this answer



                            share|improve this answer






                            New contributor




                            Matija Nalis is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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                            answered 18 mins ago









                            Matija NalisMatija Nalis

                            1013




                            1013




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