Midgress traffic is the requests/responses which happen between two edge servers. There can be several reasons/factors that may contribute to higher midgress traffic namely:
- Image Manager: Traffic from Edge to the midtier server is considered Midgress traffic between The traffic from image Servers to origin to fetch the original image was earlier classified as Midgress, but it is since automatically being waived in the billing system.
- Tiered Distribution: response traffic between the mid-tier servers (cache hierarchy)to the edge servers users connect to.
- SureRoute: For non-cacheable content, when the traffic that flows between the SureRoute servers and the Edge server.
- ICP peering: For cacheable content, Akamai usually requests its peer server for the presence of the content as the response is faster than going out to the network to fetch from a cache hierarchy or origin server.
- SiteShield: When SiteShield is enabled, Akamai introduces a hierarchy of servers for cacheable and non-cacheable content. Only these sets of servers contact the origin. Hence, traffic that flows between the SiteShield servers and the Edge servers also constitutes the Midgress.
- Pre-fetching: This feature improves the end-user experience as the prefetched content serves faster but could contribute high Midgress traffic than the edge (egress) traffic as there could be more contents prefetched than what the end-users requested for.
- Large File Optimization (LFO): A single client GET request (Edge response 200 OK Edge HIT) may trigger several hundred Partial Object Caching (POC) forward requests (which is part of LFO) to a Mid-tier Edge server (Midgress 206 OK partial response HIT) for fragments of a single large file.
- ESI: There may be other factors such as the Edge side includes (ESI)that also contribute to the Midgress traffic.