Link Level Retransmissions Issues
		n How many times to retransmit at the link level before giving up? – Finite bound -- semi-reliable link layer – No bound -- reliable link layer n What triggers link level retransmissions? – Link layer timeout mechanism – Link level acks (negative acks, dupacks, …) – Other mechanisms (e.g., Snoop, as discussed later) n How much time is required for a link layer retransmission? – Small fraction of end-to-end TCP RTT – Large fraction/multiple of end-to-end TCP RTT