Middleboxes come in all shapes and flavors. The most popular are firewalls:
- [ Check Point VPN-1 & FireWall-1 NG Performance Tuning Guide|http://www.checkpoint.com/techsupport/documentation/FW-1_VPN-1_performance.html]
Examples of experienced performance issues
Two examples in the beginning of 2005 in SWITCH:
- HttpProxy: very slow response from a webserver only for a specific circle of people
- GatewayProxy: tcp transfers get stalled as soon as a packet is lost on the local segment from the middlebox to the end host.
A Cisco IOS Firewall in August 2006 in Funet:
- WindowScalingProblems: when window scaling was enabled, TCP performance was bad (10-20 KBytes/sec). Some older versions of PIX could also be affected by window scaling issues.
DNS Based global load balancing problems
- Counting IPv6 DNS
This firewall (up to at least version 11.4R3.7) performs fragment reassembly in order to apply certain checks to the entire datagram, for example in "DNS ALG" mode. It then tries to forward the reassembled packet instead of the initial fragments, which triggers ICMP "packet too big" messages if the full datagram is larger than the MTU of the next link. This will lead to a permanent failure on this path, because the (correct) fragmentation at the sender is annihilated by the erroneous reassembly at the firewall.
The same issue has also been found with some models of the Fortigate firewall.
– Main.ChrisWelti - 01 Mar 2005
- Main.PekkaSavola - 10 Oct 2006
-- Main.PekkaSavola - 07 Nov 2006
-- Main.AlexGall - 2012-10-31