816d5c23   
   XPost: comp.arch.embedded, sci.electronics.design   
   From: gah@ugcs.caltech.edu   
      
   In comp.protocols.tcp-ip Didi  wrote:   
   > On Mar 29, 7:37?am, "JosephKK" wrote:   
   (snip)   
      
   >> APR lower level than UDP? ?I don't think so. ?Same   
   >> level at best, below UDP is MAC and PHY only.   
      
   > Uhm, not so sure. Same level as UDP in that they both have the   
   > Ethernet protocol type set to "internet", perhaps; but the   
   > data inside a UDP packet are encapsulated into that level,   
   > whereas the ARP data are purely Ethernet encapsulated.   
   > This should put it one level lower - at least unofficially?   
      
   MAC at layer 2 (ethernet switch level), IP at layer 3,   
   TCP and UDP at layer 4.   
      
   Sometimes I think that ICMP should be layer 4 (as in ping),   
   other times in layer 3.  It does go inside an IP packet.   
      
   ARP does not have the IP (X'0800') ethernet type, so it   
   seems that it should also be layer 3.   
      
   -- glen   
      
   --- SoupGate-Win32 v1.05   
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