![]() The way that these transport layer checksums are computed have virtually identical performance for IPv4 and IPv6. These checksums are functionally equivalent and the computation of the checksum is only slightly different for IPv4 and IPv6. There are TCP checksums for IPv4 and IPv6 and UDP checksums for IPv4 and IPv6. Both IPv4 and IPv6 use checksums for TCP and UDP packets. Even though IPv6 packets are larger, they can still be hardware accelerated like IPv4 and the performance difference is negligible.īoth IPv4 and IPv6 protocols support the same transport layer protocols above them. ![]() Another difference between IPv4 and IPv6 is that IPv4 packets may be variable in length while the basic IPv6 header is a fixed 40-bytes. IPv6 still uses a Hop Limit value within its header and that is decremented every Layer-3 hop along the transmission path, but that does not result in any header checksum calculation. ![]() IPv6 does not have any type of header checksum. We now have higher quality copper connections and cables and far greater use of fiber optic communications with vastly better error rates than links from the 1980s. In contrast, IPv6 was created when transmission link quality was improving. This all adds up to lots of checking to determine if a bit error has occurred, adding to the protocol overhead, and potentially decreasing performance. There are methods to detect bit errors at Layer-1, there are checksums at Layer-2, a checksum in the header at Layer-3, and TCP implements options for retransmissions, of course, so applications can check if an error occurred in the payload. This results in the router having to re-compute the header checksum each hop along the transmission path. With IPv4, as each packet is forwarded across a Layer-3 hop, the header Time To Live (TTL) value is decremented by one. Therefore, IPv4 implements a header checksum to determine if there is an error in the fields in the IPv4 header itself. IPv4 was created at a time when WAN transmission links were prone to bit errors. IPv6 performance is streamlined as a result of its native communication.Ĭhecksums for Determining IP Packet Bit Errors Refreshingly, IPv6 does not need or use any NAT or PAT functionality and restores the native end-to-end nature of the IP protocol. ![]() Lee Howard has given presentations on the TCO for CGN and has concluded that service providers should work to deploy as little CGN as they can get away with. As ISPs explore the use of Carrier Grade NAT (CGN), they start to understand how this can negatively impact their end-user experience by negatively affecting some applications. There are many benefits to avoiding the use of NATs. The packet manipulation performed by the NAT function can add latency and jitter to IPv4 packets. As a result, there is congestion, not for Internet bandwidth, but for TCP/UDP port space and limited IPv4 address pool resources. Many applications create many connections and with numerous users behind a single NAT/PAT. The NAT/PAT system then has to maintain connection state, reversing the process on the response packets, so that the return traffic can reach the original packet source. The packet is then forwarded on to the IPv4 destination address. For IPv4, every time a packet crosses a NAT/PAT middle-box, the packet source address is re-written, and the TCP/UDP source port is changed. IPv6 uses global addresses and typically does not rely on NAT in any way. One of the key differences between IPv4 and IPv6 is that IPv4 relies heavily on Network Address Translation (NAT) and Port Address Translation (PAT) due to IPv4 address exhaustion. Now, let’s consider the IPv6 protocol and see if there are any fundamental characteristics of IPv6 that could make it faster in certain circumstances. Similar to the measurements of the amounts of IPv6 traffic observed on the Internet, it depends on where you take your measurements. Facebook’s Paul Saab concluded that their customers experience faster performance over native IPv6. Geoff Huston’s research concluded that IPv4 and IPv6 can be equivalent in many cases. In the first part of this blog, we reviewed some recent studies on the performance of IPv6 compared with IPv4.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |