A very common question I have been asked many times is the difference between Edge Traffic and Midgress Traffic.
Midgress traffic is the requests/responses which happen between two edge servers. This traffic is typically seen when Tiered Distribution, SureRoute or SiteShield are enabled/used.
There are few factors that contribute to the midgress traffic (traffic flowing between Akamai servers), namely:
- Tiered Distribution: response traffic between the parent servers (cache hierarchy) to the edge servers users connect to.
- Sureroute: For uncacheable content, when the traffic that flows between the Sureroute parent 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 teh network to fetch from a cache hierarchy or origin server.
- Siteshield: When Siteshield is enabled, Akamai introduces a hierarchy of servers for cacheable and uncacheable content. Only these parent servers contact the origin. Hence, traffic that flows between the Siteshield servers and the Edge servers also constitutes the midgress.
- Prefetching: This features improves 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.
- ESI / LFO: There may be other factors such as Edge side includes (ESI), Partial object caching / Large file optimization (POC / LFO) that also contribute to the midgress traffic.
Understanding where midgress traffic comes from can be very beneficial. You can always check the Monitor > Offload report to find out more about Edge Traffic vs Midgress Traffic and of course Origin Traffic.