Packet Encapsulation and Link Bonding Protocols
|Overture’s market segment of Carrier Ethernet includes equipment that supports a wide array of protocols and encapsulations. How these protocols interact with each other can be very confusing. This blog provides a handy infographic that clarifies the relationships between and among these protocols.|
The point of the infographic below is to provide a visual map of the relationship of the myriad protocols and encapsulations involved in Carrier Ethernet. It is targeted for engineers and product managers that work with Carrier Ethernet equipment.
The infographic shows three levels of protocols and encapsulations. Each service protocol may feed into one or more encapsulating protocols and on to media mappings and bondings, as indicated by the arrows.
Click on the infographic for a high-resolution image.
Legend for the Infographic
The layers are:
- Service Protocols – This infographic is focused on Carrier Ethernet, so the main protocols of interest are Ethernet itself, and its primary payload of IP.
- Encapsulations – These protocols serve to map the IP and Ethernet packets into various media. Often, several layers of protocols are needed to handle multiple payload types and/or to bond media links.
- Media Mappings – These are specifications for the physical media itself along with payload and/or bonding options. Note that some of the media such as T1s can either be the final physical layer, or can be mapped to a higher speed protocol such as DS3 or SONET.
Examples of Using the Infographic
Same protocol, different uses
Some of the depicted protocols are multipurpose, such as PPP/RFC1661. PPP can carry Ethernet frames or IP packets, but equipment configured for PPP carrying IP (using IPCP/RFC1332) won’t work directly with equipment configured for PPP carrying Ethernet (using BCP/RFC3518), even if the Ethernet is carrying IP. That relationship is shown clearly in the infographic.
Different encapsulations that look similar
Some encapsulations are confusingly similar. ITU G.8040 and G.7043 both support carrying Ethernet in GFP frames over T1s and DS3s. However, G.8040 is for single T1s or DS3s, while G.7043 is for bonded T1s or DS3s. Again, equipment supporting G.8040 won’t work with equipment supporting G.7043. This can be determined by following the respective paths for G.8040 and G.7043.
Same media, different encapsulations
A single media such as a clear channel OC-n (or STM-n) can carry Ethernet frames with a variety of encapsulations, such as POS/RFC2615, EoLAPS/X.86 and GFP/G.7041.
Same media, different bondings
Links such as T1s or E1s can be bonded in a variety of ways, including MLPPP/RFC1990, VCAT/G.7043 or EFM/802.3ah.
About the Author
Prayson Pate is Chief Technologist and co-founder at Overture. Prayson is a technology evangelist with a proven track record leading teams and delivering products. Since 1983 he has been building Carrier Ethernet and telecom products for service providers and network operators around the world - both as an individual developer and as a leader of development teams. Prayson spends much of his time driving adoption of Overture's new Ensemble Open Service Architecture, which includes aspects of automation, virtualization, SDN and NFV. He has a BSEE from Duke, an MSECE from NC State and is the holder of nine US patents.