A lost packet in G.711 is handled by DSP. The DSP knows where the last packet level ended, if a packet is lost, it simply resends the last packet is received. Since it is either a 10 or 20 ms slice, it will not be noticed. The real problem is with consecutive lost packets. We use a method where since we know the level where the last packet ended, we can start the next one there and guess at the next missing packet. G.711 is very tolerant. The compressed codecs actualy have a harder time and the effects of lost packets may take 2 or 3 seconds to fully recover.