Link Layer: setting the context error actual PDu flow di dI dI Router r1 application app ication transport network net ork data link data link data link physical dIdI d protocol I di d physica Host H1 ph/ph/Ph 回p回 network Host H2 Router R2 Router r3 Router R4 5: DataLink Layer 5a-25: DataLink Layer 5a-2 Link Layer: setting the context