LAN and SAN Separation

  • Security  Ensures protection from hacking
  • Bandwidth – SAN needs more bandwidth than LAN
  • Flow Control – SAN is lossless and LAN is lossy
    • Ethernet Flow control ( LAN ):
      • Source transmits packets untill receiver buffer overflow, then sends a “Pause” frame
      • Lost packets are retransmitted
    • Fibre Channel ( SAN ):
      • Credit based mechanism – Receiver has control
      • Source does not send a frame until the receiver telsl the source it can receive a frame by sending “Ready” signal Back
  • Performance – SAN provides more performance than LAN enviorments

LAN vs SAN flow control

  • Flow control is how data is controlled in a network
  • Ethernet Flow control ( LAN )
    • Source transmits packets until receiver buffers overflow, then sends a “Pause” frame
    • Lost packets are retransmitted
  • Fibre Channel ( SAN )
    • Credit based mechanism – Receiver has control
    • Source does not send a frame until the receiver tells the source it can receive a frame by sending “Ready” signal back.
    • “Lossless Fabric”

FibreChannel

  • San Topologies
    • Point-to-Point
      • Initiator (server) and Target (Storage) directly connected
    • Arbitraded Loop (FC-AL) (Legacy)
      • Logical ring topology, similar to token ring
      • Implies connection is required on the ring
    • Switched Fabric ( FC-SW ) ( Standard)
      • Logical equivalent to a switched ethernet LAN
      • Switches manage the fabric allowing any-to-any communication
      • Support more than 16 million device addresses
  • FibreChannel Port types
    • N_port – Node Port
    • NL_port – Node Loop Port
    • F_port – Fabric Port
    • FL_port – Fabric Loop Port
    • E_port – Expansion Port ( ISL )
    • TE_port – Trunking Expansion Port
  • FC Addressing is analogous to IP over Ethernet
    • IP addresses are logical and manually assigned
    • Ethernet MAC Addresses are physical and burned in
    • FC World Wide Names ( WWNs )  / MAC / Zoning

      • 8 byte address burned in by manufacturer
      • Word Wide Node Name
      • World Wide Port Name
    • FC Identifier ( FCID )  / IP / Routing

      • 3 byte logical address assigned by fabric
      • FCID is subdevided into three fields:
        • Domain ID
          • Each switch gets a domainID
        • Area ID
          • Group of ports on a switch have an Area ID
        • Port ID
          • End station connected to switch gets a Port ID
  • FibreChannel Nameserver ( FCNS)
    • analogous to ARP cache
    • Used to resolve WWN ( pysical address ) to FCID ( logical address )
    • Like FSPF, FCNS requires no configuration
  • FibreChannel Logins
    • Ethernet networks are connectionless
    • Fibre Channel networks are connection oriented
      • All end stations must first register with the control plane of the fabric before sending any traffic.
    • Fabric Registration has three parts
      • Fabric Login ( FLOGI)
      • Port Login ( PLOGI)
      • Process Login ( PLRI )
    • sh flogi database
    • sh fcns database
  • VSANs
    • Logical seperation of SAN traffic
  • Zoning
    • like an ACL in the IP world